Oleoresins from Capsicum spp.: Extraction Methods

Oleoresins from Capsicum spp.: Extraction Methods and Bioactivity

Guiomar Melgar-Lalanne, Alan Javier Hernández-Álvarez, Maribel JiménezFernández & Ebner Azuara Food and Bioprocess Technology An International Journal ISSN 1935-5130 Volume 10 Number 1 Food Bioprocess Technol (2017) 10:51-76 DOI 10.1007/s11947-016-1793-z

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Author's personal copy Food Bioprocess Technol (2017) 10:51–76 DOI 10.1007/s11947-016-1793-z

ORIGINAL PAPER

Oleoresins from Capsicum spp.: Extraction Methods and Bioactivity Guiomar Melgar-Lalanne 1 & Alan Javier Hernández-Álvarez 2 & Maribel Jiménez-Fernández 1 & Ebner Azuara 1

Received: 7 January 2016 / Accepted: 16 August 2016 / Published online: 9 September 2016 # Springer Science+Business Media New York 2016

Abstract Capsicum spp. fruit is one of the most produced vegetables around the world, and it is consumed both as fresh vegetable and as a spice like a food additive for their characteristic red color and, in many cases, its pungency. In addition to its economic importance, the bioactivity of some important compounds such as capsaicinoids and carotenoids has promoted its research. The use of Capsicum oleoresins has been increased due to its advantages comparing with the traditional dry spice. These include obtaining higher quality products with the desired content of bioactive and flavored substances. The wide diversity of extraction methods including water extraction, organic solvent extraction, microwave-assisted extraction, and ultrasound assisted extraction as well as supercritical fluid extraction among others are discussed in the present review. Moreover, pretreatments such as chemical treatments, osmotic dehydration, sun and oven drying, and freeze-drying commonly used before the extraction are also presented. Due to its importance, Capsicum oleoresins produced with Bgreen^ solvents and the improvement of fractional extraction techniques that allow to obtain separately the various bioactive fractions will continue under research for further development.

Keywords Capsicum spp. extraction . Oleoresin . Essential oil . Bioactivity . Antioxidant activity

* Ebner Azuara [email protected] 1

Instituto de Ciencias Básicas, Universidad Veracruzana, Av. Dr. Luis Castelazo Ayala s/n. Col Industrial Ánimas, 91192 Xalapa, Veracruz, Mexico

2

Food Research and Development Center, Agriculture and Agri-Food Canada, 3600 Casavant West, St. Hyacinthe, QC J2S 8E3, Canada

Introduction The Capsicum genus consists, up to date, of 31 species, five of which are used as fresh vegetables and species: Capsicum annum, Capsicum baccatum, Capsicum chinense, Capsicum frutescens, and Capsicum pubescens (Moscone et al. 2007). The center of domestication and dispersal patterns of these species remains speculative, although it has been suggested that C. annum was initially domesticated in Mexico, C. frutescens in the Caribbean, C. baccatum in Bolivia, and C. pubescens in south of the Andes (Perry et al. 2007). In general, Capsicum spp. are commonly divided/distributed/ split into two main groups, depending on their Scoville heat units (SHU), a measurement of their pungency: sweet or nonpungent fruits (syn. bell pepper, pepper, paprika, moron chili, or sweet chili) and hot or pungent fruits (syn. chili, red pepper, hot pepper, spicy pepper, cayenne, hot paprika). Only in Mexico, there are about a hundred cultivars of hot Capsicum spp., more or less spicy, more or less large, with a long or rounded shape and colors varying from pale yellow to dark red. Some varieties of C. annuum L. (Serrano, Jalapeño, Poblano, Guajillo) and C. chinense (Habanero) are currently cultivated worldwide (Katz 2009). Their particular characteristics of pungency, aroma, and flavor made this product an important ingredient in millions of people’s daily diets (Meckelmann et al. 2015). In many Latin American and Asian countries, it is an essential part of their daily cooking; in India, it is a basic ingredient in the traditional curry blends, and in the Mediterranean region, it is widely used as dye, preservative, and seasoning in many meat sausages both fresh and dehydrated. Green and red bell peppers at different maturity stages can be from the same cultivar. Green fruits are immature and usually consumed as fresh or minimally processed vegetables and red fruits are consumed both as fresh vegetables and as spice (as powder). Nowadays, red

Author's personal copy 52

dehydrated fruits in powder or as oleoresins are commonly used to modify color and flavor of many dishes such as soups, stews, sausages, cheese, snacks, salad dressings, pizza, confectionaries, and beverages (Arimboor et al. 2015). Moreover, dehydrated chili powder is used in poultry feed as egg pigment and as prophylactic antimicrobial against some pathogens (Vicente et al. 2007; Lokaewmanee et al. 2013). Fruits of Capsicum spp. vary in color, sharp, and size between and within species. Ripe fruits display a range of colors from white to deep red. The intensity of red color and the degree of pungency are valued as major quality parameters. The pungency depends on capsaicinoids content which in turns depends on the variety and maturation stage and is commonly measured in Scoville heat units (SHU). The red color is imparted mainly by carotenoids with more than 50 identified structures. Capsainthin, capsorubin, and cryptocapsin impart brilliant red color to ripen fruits while the yellow orange color is given by βcarotene, zeaxanthin, violaxanthina, and b-cryptoxantin (Hornero-Méndez and Mínguez-Mosquera 2001; CervantesPaz et al. 2012). Capsicum spp. fruits are considered as nonclimacteric fruits. Green or deep green harvest fruits have failed to reach a fully red color after harvest while fruits that were harvested at or after the breaker stage completed their color change to a fully red. However, the different color stages in mature fruits affect the color development and quality, but not the pungency level. Therefore, to ensure the highest quality, it is necessary to harvest the fruit when a completely red color has been developed in the plant (Krajayklang et al. 2000). Despite being one of the most consumed vegetables worldwide, there is scarce information about the proximate composition of different commercial Capsicum spp. both in dried or fresh forms (see Table 1) and, in general, is incomplete. Only Esayas et al. (2011) determined fiber as crude fiber and carbohydrates as available carbohydrates, and Abdou Bouba et al. (2012) also determined the available carbohydrates, but not crude fiber hinders the comparison with the rest; most of authors determined the total carbohydrates. Most of the articles do not specify the botanical species of the analyzed chili or the maturity grade. In commercial dried Capsicum spp., moisture varies from 5.5 to 13.0 g/100 g of fresh sample while in fresh Capsicum spp. the moisture varies from 89.90 to 94.1 g/ 100 g fresh sample, depending the variety analyzed. Orellana-Escobedo et al. (2013) found the highest differences in carbohydrate (between 69.9 and 58 g/100 g), similar to Esayas et al. (2011) who found similar quantities of carbohydrates and crude fiber in common dried Capsicum spp. Finally, only Abdou Bouba et al. (2012) found minor quantities of carbohydrates in bird Capsicum (7.0 g/100 g) calculated as available carbohydrates without the incorporation of the fiber fraction, but without consider it. Protein is the less variable parameter both in dried and fresh samples, and the fat portion ranges between 4.2 and 13.8 g/100 g in dried samples and from 0.16 to 0.54 g/100 g in fresh samples. It is

Food Bioprocess Technol (2017) 10:51–76

important to highlight that the maturity grade affected the proximate chemical composition, color, total capsaicinoids, and ascorbic acid contents in analyzed samples (Zaki et al. 2013; Martínez et al. 2007). There are several groups of valuable compounds in Capsicum spp. including carbohydrates, which constitute approximately 85 % of the dry weight, polyphenols (0.5 % of dry weight) and minor but important compounds such as capsaicinoids, carotenoids, and vitamins (Arimboor et al. 2015). The physico-chemical parameters and mineral composition depend directly on the maturity stage of the fruit. The soluble solid content and titratable acidity increase during ripening as well as the fat, the protein, and the ascorbic acid content (Martínez et al. 2007). The flavor profile of Capsicum spp. from several parts of the world has been reported in many studies describing the changes in volatile organic compounds during ripening, showing that the producer aroma compounds differ significantly during the maturity process (Liu et al. 2009). In the food industry, the presence of pungent principles (capsaicinoids) in oleoresins of hot Capsicum spp. may represent a limitation for its application as a food dye and restricts the exploration of a large number of high yielding pungent varieties. Efforts to improve extraction methods to prepare non-pungent oleoresins from pungent Capsicum fruits by the selective removal of capsaicinoids are in continuous research mostly focused in the development of fractionated extraction techniques (Arimboor et al. 2015).

Drying as Pretreatment for Extraction Chemical Pretreatments The use of chemical pretreatments such as sodium and potassium hydroxide, potassium meta bisulphate, potassium carbonate, methyl and ethyl ester emulsions, and ascorbic and citric acid have been suggested to obtain better quality characteristics of dehydrated Capsicum spp. (see Table 2). Therefore, the treatment with ethyl oleate and citric acid solutions before the drying process can reduce the drying time and the mass-transfer resistance both in red pepper (Doymaz and Kocayigit 2012) and green pepper (Doymaz and Ismail 2013). Red C. annuum L. previously treated with a solution containing NaCl, CaCl2, and Na2S2O3 prior to drying at 70 °C showed the best firmness and color quality (Vega-Gálvez et al. 2008). The use of a pretreating solution with 2 % of ethyl oleate and 5 % of K2CO3 was found to be effective to provide the best yield and color quality in Capsicum spp. dried at 50 °C. Moreover, pretreated fruits dried faster and were found to have the highest drying rate. Color analysis showed that red color is preserved better in pretreated fruits and in slices (Doymaz and Pala 2002). Similar results were obtained in oven-drying previously treated with ethyl oleate and citric

Author's personal copy Food Bioprocess Technol (2017) 10:51–76 Table 1

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Proximate chemical composition (g / 100 g) of different commercial Capsicum spp.

Common name

Fresh/dried Moisture

Ash

Protein

Fat

Fibera

Carbohydrateb Reference

Ancho

D

7.8 ± 0.0

12.0 ± 0.1

9.8 ± 0.1

nd

60.2 ± 2.3

10.1 ± 0.1

c

Orellana-Escobedo et al. 2013

Bako

D

9.0 ± 0.2

7.3 ± 0.1

8.7 ± 0.4

9.5 ± 0.1

26.0 ± 1.3

39.5 ± 0.9

Esayas et al. 2011

Bird

D

9.3 ± 0.1

9.4 ± 0.2

9.4 ± 0.8

11.1 ± 0.2

nd

60.8 ± 0.1

Abdou Bouba et al. 2012

Chipotle

D

8.8 ± 0.2

6.9 ± 0.2

12.7 ± 0.0

8.6 ± 0.8

nd

63.0 ± 1.2


Chipotle meco

D

8.5 ± 0.4

9.5 ± 0.2

15.2 ± 0.5

9.1 ± 0.0

nd

57.7 ± 1.1


De arbol

D

5.6 ± 0.2

8.8 ± 0.6

12.7 ± 0.6

13.4 ± 1.0

nd

59.4 ± 0.4


Guajillo

D

9.1 ± 0.6

7.5 ± 0.0

12.8 ± 0.1

12.4 ± 0.1

nd

58.0 ± 0.6


Habanero

D

13.0 ± 2.0

7.5 ± 0.0

13.5 ± 0.4

4.6 ± 0.2

nd

61.3 ± 2.4


Jalapeño

D

10.1 ± 0.9

7.3 ± 0.1

14.3 ± 0.4

4.2 ± 0.2

nd

64.0 ± 0.8


Marako fana

D

9.2 ± 0.1

5.3 ± 0.6

11.8 ± 0.1

11.2 ± 0.2

27.3 ± 0.2

35.3 ± 0.6c

Esayas et al. 2011

Mirasol

D

9.9 ± 0.2

9.6 ± 0.1

14.1 ± 0.4

7.5 ± 0.1

nd

59.0 ± 0.5


Morita

D

10.7 ± 0.9

8.6 ± 1.4

14.1 ± 0.6

7.6 ± 0.2

nd

59.0 ± 1.3


Oda haro

D

8.8 ± 0.1

7.3 ± 2.2

9.2 ± 0.2

9.2 ± 0.4

28.6 ± 0.8

37.1 ± 2.1c

Esayas et al. 2011

Pasado

D

8.9 ± 0.5

7.2 ± 1.2

12.6 ± 0.3

5.4 ± 0.1

nd

66.2 ± 1.0


Pasilla

D

7.6 ± 0.2

5.8 ± 0.0

12.3 ± 0.9

13.8 ± 0.3

nd

60.5 ± 0.8


Pepper

D

5.70 ± 0.1

4.35 ± 0.1

11.7 ± 0.1

12.7 ± 0.1

2.6 ± 0.0

62.9 ± 0.0c

Otunola et al. 2010

Piquin

D

5.5 ± 0.1

7.3 ± 0.0

13.7 ± 0.3

11.0 ± 1.0

nd

62.5 ± 1.1


Puya

D

7.0 ± 0.2

7.8 ± 0.1

13.2 ± 0.3

8.1 ± 0.7

nd

63.8 ± 1.3


Serrano

D

11.2 ± 0.4

5.8 ± 0.0

12.8 ± 0.6

2.3 ± 0.1

nd

67.9 ± 0.8


Tres venas

D

9.0 ± 0.0

7.0 ± 0.2

13.3 ± 0.6

9.6 ± 0.1

nd

61.0 ± 0.3


Arnoia (green )

F

92.7 ± 1.4

0.40 ± 0.08 0.80 ± 0.15 0.22 ± 0.04 1.63 ± 0.24 3.84 ± 0.78

Martínez et al. 2007

Arnoia (green B)

F

93.7 ± 0.1

0.33 ± 0.02 0.71 ± 0.07 0.16 ± 0.03 1.31 ± 0.15 3.51 ± 0.18


Arnoia (red)

F

Green bell pepper F

89.90 ± 1.2 0.62 ± 0.09 1.13 ± 0.21 0.54 ± 0.15 1.62 ± 0.15 6.23 ± 1.36


92.56

Faustino et al. 2007

0.3

1.05

0.38

0.73

4.98

nd not determined a

When determined calculated as crude fiber

b

Determined as total carbohydrates at least otherwise stated

c

Available carbohydrates

acid solutions where the drying, rehydration, and color characteristics were significantly influenced by air temperature and pretreatments (Doymaz and Kocayigit 2012). The color of paprika is drastically affected by the drying process of red peppers through non-enzymatic reactions that gives the powder a brown tonality. To solve this, the dip in a solution of 2 % of ethyl oleate solutions plus 2 % of NaOH and 4 % of K2CO3 and an air drying temperature of 60 °C is a good solution that retains the red color of the original fruit (Ergüneş and Tarhan 2006). Sodium metabisulfite at a drying temperature of 70 °C can provide a more bright red color because the sulfite inhibits the non-enzymatic browning reactions. Moreover, soaking the Capsicum in sodium metabisulfite combined with CaCl2 produced the highest color stability (Wiriya et al. 2009). Blanching inactivates deteriorative enzymes such as peroxidase isoenzymes and reduces the microbiological rate and improves the color characteristic of the fruits (Schweiggert et al. 2006). In non-pungent C. annuum L. shreds in boiling

water (3 min) followed by pre-treatments with 0.20 % of potassium metabisulfite and 0.50 % of citric acid for 5 min before drying in a solar poly tunnel produced a dehydrated product with high color quality and stability cid (Sharma et al. 2015). Blanching of sweet C. annuum L. at 95 °C for 5 min improved the drying rate by reducing the process time (Vengaiah and Pandey 2007). In pungent Capsicum spp., blanching slightly reduces the initial capsaicinoids content but avoids their oxidation during storage (Schweiggert et al. 2006). Osmotic Dehydration Osmotic dehydration is a process for the partial removal of water in which cellular materials are placed in a concentrated solution of soluble solute through semi-permeable membrane results in the equilibrium conditions in both sides of membrane (Arvanitoyannis et al. 2012). It has been used for improving the quality of fruit products and reducing energy

Author's personal copy 54 Table 2

Food Bioprocess Technol (2017) 10:51–76 Chemical pretreatments used before drying Capsicum spp.

Species

Common name

Treatment conditions

Chemical pretreatments

Room temperature / 1 min a) 2 % ethyl oleate +4 % K2CO3 b) 2 % ethyl oleate +5 % K2CO3 a c) 2 % ethyl oleate +6 % K2CO3 C. annuum L. Charliston Room temperature / 1 min a) 2 % ethyl oleate +3 % K2CO3 a b) 0.5 % Citric acid C. annuum L Green bell pepper Room temperature / 1 min a) 2 % ethyl oleate +3 % K2CO3 a b) 0.5 % Citric acid C. annuum

Kahramanmaras

C. annuum L. Paprika

23 °C / 1 min 60 °C / 1 min

C. annuum L Lamuyo variety

25 °C /10 min

C. annuum L Huarou Yin

90 °C / 3 min

a

Reference Doymaz and Pala 2002

Doymaz and Kocayigit 2012 Doymaz and Ismail 2013

a) 2 % Ethyl oleate (33 °C) Ergünes and Tarhan 2006 b) 2 % ethyl oleate +2 % NaOH (23 °C) c) 2 % ethyl oleate +2 % NaOH +4 % K2CO3 (23 °C) d) 2 % Ethyl oleate (60 °C) e) 2 % ethyl oleate +2 % NaOH (60 °C) f) 2 % ethyl oleate +2 % NaOH +4 % K2CO3 (60 °C) a 20 % NaCl +1.0 % CaCl2 + 0.3 % NaS205 Vega-Gálvez et al. 2008 a) 0.3 % NaS205 b) 0.1 % ascorbic acid c) 0.3 % NaS205 + 1 % citric acid d) 0.3 % NaS205 + 1 % CaCl2a

Wiriya et al. 2009

Best attributes found

consumption. It is used to reduce the water content of the food from 30 to 70 % as an upstream step of the dehydration of food before they are subjected to further processing such as freezing, freezing-drying, vacuum drying, and air drying (Levent and Ferit 2014). Since osmotic dehydration as a pretreatment of many processes improves nutritional, sensorial, and functional properties of food without changing its integrity, it was exploited as a pretreatment to Capsicum spp. dehydration. During osmotic treatment, mass transfer occurs through semi-permeable cell membranes present in biological materials, which offers the dominant resistance to the process. The state of the cell membrane can change from being partially to totally permeable, and this can lead to significant changes in tissue architecture. Various osmotic agents such as sucrose, glucose, fructose, corn syrup, sodium chloride, and their combination have been used for osmotic dehydration (see Table 3). The addition of small quantities of sodium chloride to osmotic solutions increased the driving force of the drying process and synergistic effects between sucrose and sodium chloride have been reported (Ade-Omowaye et al. 2002). In general, osmotic dehydration pretreatment has a positive effect in the color and other quality attributes of the final dehydrated Capsicum both in the case of red (Falade and Oyedele 2010) and green fruits (Quintero-Chávez et al. 2012). In red Capsicum, a pretreatment with sucrose solutions from 40 to 60° Brix resulted in a significant effect on the conservation of redness value (a*), a mark of color quality of dry red Capsicum (Falade and Oyedele 2010). The osmotic dehydration in greenyellow Padron pepper (C. annuum L. Longum) could be considered as an impregnation process because the solid gain, the

weight reduction, and the water loss increased with the temperature and salt concentration. However, the concentration of NaCl did not develop significant changes in color working at lowest temperatures (25 °C) (Chenlo et al. 2006). The great limitation of osmotic dehydration is that the final product shows an intermediate humidity and the product cannot be considered shelf stable (Levent and Ferit 2014). Most studies related with the color stability have been done in red fruits. However, in green fruits, an important conservation of color was also found (Chenlo et al. 2006) using a combination salt–sorbitol (Ozen et al. 2002; Ozdemir et al. 2008). Salt–sorbitol combination significantly increases weight loss, solids gain, and tissue brix and decreased water activity in green fruits. Moreover, the presence of sorbitol hindered the entrance of salt into the product improving the sensorial properties of the final product (Ozen et al. 2002; Ozdemir et al. 2008). Temperature is another important parameter to take account because high temperatures can affect the structure of the fruit in a similar way that blanching and room temperatures are preferred. Red C. annuum (varieties Sombo, Rodo, Bawa and Tatase) osmotically dehydrated with sucrose or a combination of sucrose–salt was tested, resulting to higher sucrose concentrations that gave better results while improved solute gain were obtained using binary mixture with lower processing time, energy, and cost. Moreover, this pretreatment protects the fruits against the discoloration in the posterior sun drying process (Raji Abdul Ganiy et al. 2010). The salt (NaCl) also has different effects on osmotic dehydration, depending of the salt source, concentration, temperature, and time. Best results have been found with saturated sea salt at 25 °C (Levent and Ferit 2014).


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Osmotic dehydration treatments used in Capsicum spp.

Species

Common name

Treatment conditions

Osmotic solution

Fruit: solution ratio (w/w)

Reference

C. annuum

Red paprika

25 °C 5h 30 °C, 30, 60 min

Sucrose (5 to 45 %) and NaCl (0 to 15 %) Sucrose: NaCl (21.86:2.02 )

1:25

Ade-Omowaye et al. 2002

1:10

Ade-Omowaye et al. 2003

25 °C 90 min 20, 30, 40 °C 9h

Sucrose /NaCl 1:3 (w/w)

1:4

Da Silva et al. 2012

Sucrose (40, 50, 60 brix) Sucrose 50 brix + NaCl (5, 10, 15 %)

1:10

Raji Abdul Ganiy et al. 2010

40, 60 °C 18 min

NaCl (7.5, 5, and 2.5 %)

Hernández et al. 2009

Common salt (20 %, 30 %, saturated) Sea salt (20 %, 30 %, saturated) Sucrose: NaCl 1:3

1:2 1:3 1:4 1:20

1:4

da Silva et al. 2012

C. annuum L.

Red bell pepper Moema

C. annum C. frutescens

C. chinense

Rodo (hot) Tatase (bell) Sombo Bawa Habanero

C. annuum L.

Maras (red pepper)

25, 35, 45 °C 30, 60, 90, 120 min

C. chiense

Moema

25 °C, 90 min

C. annuum C. frutensces

9h 30 °C

Sucrose (40, 50, 60 brix)

–

Falade and Oyedele 2010

C. annum

Rodo tatashe Shombo Bawa Jupiter (green bell)

Ozdemir et al. 2008

Fresh green bell pepper

NaCl (0–10 g) and/or sorbitol ( 0–10 g) 5.5. g NaCl +6 g Sorbitol NaCl (2–10 %) and /or Sorbitol (0–10 %)

1:3

–

1:3, 1:6, 1: 4.5

Ozen et al. 2002

C. annum L.

Verdel (green bell)

Sorbitol (7, 24, 41 brix) or NaCl ( 30, 40, 110 g/L)

1:4

Quintero-Chávez et al. 2012

C. annuum L.

Fresh chili

20. 25, 30. 35, 40 °C 36 to 600 min 30 °C, 240 min 20, 35, 50 °C 15, 30, 60, 90, 120, 1200 min 6 to 60 min Room temperature Pressure (4.05, 44.66 and 85.33 kPa) 30 °C, 8 h

10 % NaCl +50 % sucrose

1:10

Zhao et al. 2013

In the case of red Capsicum spp. in addition to the combination sorbitol–salt (Quintero-Chávez et al. 2012), the most widely used is the combination sucrose–salt (Ade-Omowaye et al. 2002; Zhao et al. 2013). In general, the use of combined solutes results in better sensory quality attributes of dehydrated Capsicum spp. than the solutes alone (AdeOmowaye et al. 2002). The presence of high levels of sucrose reduces the saltiness and the presence of salt enhances the sucrose sweetness (Sacchetti et al. 2001). Osmotically treated Capsicum spp. in a mixed solution (10 % NaCl +50 % sucrose) had the best dehydration effect reaching 66 % in water loss and preventing the penetration of salt to some extent because of the existence of sugar showing the preferable color both in traditional drying and in microwave drying. However, the samples pretreated with osmotic dehydration and dried by microwaves at 60 W needed less drying time (Zhao et al. 2013). Similar results were obtained in other research where Capsicum was osmotically pretreated previously to be dried by microwaves concluding that the pretreatment can be used as criteria for faster drying thereby maintain final product quality (Swain et al. 2012). Similar results were observed with

Levent and Ferit 2014

the combination of pulsed electric fields and partial osmotic dehydration with sucrose–salt before air drying that enhanced the mass transfer rates and preserved the color quality of red Capsicum spp. (Ade-Omowaye et al. 2003). In intermediate humidity products, such as pickled, the osmotic pretreatment with sucrose–salt reduced the drying time to obtain a pickled product with 45 % humidity. Moreover, the acceptability was no influenced by the treatment (da Silva et al. 2012). The presence of 2.5 % of NaCl at pH 3.0, 40 °C and at chili/brine ratio 1:2 resulted in capsaicin extraction up to 25 % in Habanero chili (C. chinense) (Hernández et al. 2009). Drying To maximize the color quality in red Capsicum spp. fruits and to provide remunerative profits, it is necessary to harvest at maturity stage, when completely red fruit color is achieved (Krajayklang et al. 2000). There are many techniques to improve the shelf life of a product as the use of refrigeration, freezing as well as modified


atmospheres. However, drying is still the most common preservation method for most vegetables and spices. Drying has been successfully applied to decrease physical, biochemical, and microbiological deterioration of food products due to the reduction of moisture content to an appropriate level, which allows safe storage over a long period which results in substantial reduction in weight and volume, minimizing packing, storage, and transportation costs (Doymaz and Kocayigit 2012). However, drying is one of the most time and energyconsuming processes in the food industry. The quality of dried Capsicum fruits is assessed by a wide number of different parameters such as color, hotness, ascorbic acid content, and volatile flavor compounds (Toontom et al. 2012). To accelerate the drying process with the aim of improving the final quality of the dehydrated final product, mostly in color terms, some pretreatments can be implemented both in sun and industrial drying. Between these treatments, the use of chemical pretreatments and osmotic dehydration seen above is the most common. Usually, the term drying is used for drying under the influence of non-conventional energy sources like sun and wind, and dehydration is considered the process of removal moisture by application of artificial heat under controlled conditions of temperature, humidity, and air flow. Drying involves heat and mass transfer that results in reversible and irreversible changes (either physical or as a result of chemical or biochemical reactions) in the product (TundeAkintunde and Afolabi 2010). Drying temperature as well as the drying method used influence different factors such as the drying rate, the drying time, and the effective moisture diffusivity. Usually, there is an inverse relationship between air temperature and drying time (Kooli et al. 2007). Increased drying temperature results in reduced drying times and rates as well as increase moisture diffusivity, but in worse quality final products (Tunde-Akintunde and Afolabi 2010). In general, the quality characteristics of dried Capsicum spp. depend on cultivar, maturity, and storage conditions of the fresh fruits as well as the drying method used (Topuz et al. 2009). Energy consumption and quality of dried products are critical parameters in the selection of drying process. Moreover, to reduce the energy utilization and operational costs in the process, it is necessary and appropriate election of the drying technique. Among the technologies, sun drying, hot drying, and freeze drying have great scope for the production of quality dried Capsicum spp. Sun Drying Capsicum spp. fruits on harvesting have moisture content of 65–80 %, depending on whether partially dried on the plant or harvested while still succulent; this must be reduced to 10 % to prepared dried spice. Traditionally, this can be achieved by


sun-drying fruits immediately after harvesting without any special form of treatment. In the traditional open sun drying, the product is exposed directly to the sun allowing the solar radiation to be absorbed by the material. It is one of the most practiced, traditional, and oldest methods employed for food preservation. This technique requires an area with a large, open space, and long drying times (usually more than 10 days) (Elkhadraoui et al. 2015). It is hardly dependent on the ability of sunshine, and it is susceptible to contamination with foreign material, insects, and fungal infestations, resulting in lowquality products (Fudholi et al. 2013; Topuz et al. 2009). This low quality includes red color fading, development of browning pigment, and loss of carotenoids (Vega-Gálvez et al. 2008). However, the sun’s free energy for drying in open air is counterbalanced by a multitude of disadvantages which reduce not only the quantity but also the quality of the final product. To improve dried chili quality, some mechanical and solar dryers have been introduced for drying chili in order to decrease drying time (Vega-Gálvez et al. 2008). Between these technologies, there are promising applications of promising solar energy systems. The mild temperature mediates the selection and proliferation of microbiota that may contribute to enzymatic PG activity modifying the pectin fraction. The enzymatic activity generates rises in the calcium pectate fraction which favors the drying of the fruit with an initial low content of soluble pectins and calcium pectate. The changes in texture help during the transfer of moisture facilitating the dehydration process helping bioactive compounds such as carotenoids and capsaicinoids to remain almost unaltered. On the other hand, when the soluble pectins increases during dehydration, the process is delayed negatively affecting the carotenoid content, responsible of red color of the fruits (Gallardo-Guerrero et al. 2010). Recently, attempts have been made to develop solar equipment’s to improve upon the sun-drying techniques which lead to better use of available solar radiation, reduction in drying time and cleaner and better quality product, free from dust, dirt, and insect infestation. Greenhouse dryers showed that the moisture contented could be reduced to 16 % in 17 h instead of 24 h for traditional open sun dryers with a rapid payback of the investment (Elkhadraoui et al. 2015). A solar drying by forced convection was used to dry C. annum resulting in a 49 % saving in drying time compared with open sun drying (Fudholi et al. 2013). The use of solar tunnel dryers gave acceptable moisture content and capsaicin recovery in C. frutenscens (Yaldiz et al. 2010). Finally, a study comparing a sun traditional oven (50 and 70 °C) and microwave oven (210 and 700 W) drying behaviors of red bell pepper slices concluded that both the method as well as the temperature had a significant effect on the moisture loss rate being microwave the best method (Arslan and Özcan 2011).

Author's personal copy Food Bioprocess Technol (2017) 10:51–76

Conventional Drying Hot air drying is probably the most popular technique for drying Capsicum spp. in developed countries due to this relatively short drying time, uniform heating, and hygienic characteristics of the final product compared with sun drying. Usually, temperature ranges from 45 to 70 °C reducing drying time to less than 20 h. This temperature range provides maximum color values and minimizes the loss of volatile oils and discoloration (Arslan and Özcan 2011). However, hot air drying causes structural and physicochemical damages for the overheating during the second stage of drying as a result of shrinkage phenomenon which is taken place during the drying process. A lab-scale tray dryer using a one-temperature regime (50, 60 and 70 °C) provided a darker color for dried chili and low values of lightness (L*), chroma (C*), and hue angle (H*) compared with those when a two-stage temperature process was used (Arslan and Özcan 2011). Drying influences the chemical composition of green peppers (C. annuum L.) due to volatilization of some components, oxidation processes, and protein denaturalization, but temperature does not have a significant role in this phenomenon (Faustino et al. 2007). The radical scavenging activity showed higher antioxidant activity at high temperatures (80– 90 °C) respect to low temperatures (5–70 °C), and the ASTA color was affected by temperature and presented the lowest color value at 90 °C. Moreover, all chromatic parameters (L*, a*, b*, C*, and H) were affected by temperature. In addition, the development of the Maillard reaction which occurs in association with other events could contribute to color and antioxidant capacity (Vega-Gálvez et al. 2009). Other Drying Techniques Freeze-drying supports enzyme deactivation, thus rapidly inhibiting enzymatic oxidation offering a superior product quality. However, the final products result strongly hygroscopic that may adversely affect the moisture content and the water activity during storage. Besides, the freeze-drying increases the porosity and consequently the surface area of the product is highly exposed to the damaging activity of free radicals and oxygen. However, this sensitivity to the process depends on the freeze-drying conditions, the variety of Capsicum spp., and the part of the fruit processed (Materska 2014). Furthermore, freeze-drying of C. annuum Linn. Var. acuminatum Fingarh resulted in more bright red color than other drying methods without affecting the capsaicin concentration and with a similar sensorial profile than fresh chili. However, in spite of its great quality, freeze-drying is still a very expensive method to implant at industrial level (Toontom et al. 2012). Instant Controlled Pressure Drop stops the thermal degradation and induces swelling and possibility the rupture of the

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cell walls. This technique can be used as an alternative with high-quality final product decreasing the operation cost (Téllez-Pérez et al. 2012) with a direct impact on active molecules and functional activity in green C. annuum L. (Poblano pepper). Moreover, results showed that the process could preserve the main nutritional and sensorial characteristics of the raw material as phenolics and flavonoids (Téllez-Pérez et al. 2013). Reflectance Windows™ drying helps to prevent quality degradation of the product. In the case of Capsicum spp., this seems to be a promising processing method showing a good overall color quality, except for the ASTA values comparable with freeze-dried samples (Topuz et al. 2009). Finally, far-infrared radiation has significant advantages over conventional drying such as higher drying rate, energy saving, uniform temperature distribution, and reduced drying time, giving a better quality product (Saengrayap et al. 2015).

Conventional Extraction Procedures Water Extraction Water, used as an extraction solvent, mainly extracts the hydrophilic compounds present in vegetable materials. It is a safe and cheap solvent widely used mainly in cooking and in the preparation of water infusions. Moreover, in some cases, water can enhance the nutritionally value of some spices. Water can be added hot (boiling point) or cold (at room temperature) to the drying plan extracts refluxing for a period of time. After that, extracts are filtered and/or centrifuged. In some cases, the extracts can be freeze-dried before being analyzed (Aliakbarlu et al. 2014; Gonçalves et al. 2013). The traditional water extraction techniques usually include maceration with or without stirring, mild heating, or heating under reflux. It is the simplest and oldest extraction method. This technique requires generally long extraction times and large amounts of sample and water. The most traditional use is as infusions and the hydro-distillation (El Asbahani et al. 2015). However, the heating process may destroy thermalsensitive compounds. To improve the efficiency, ultrasoundassisted extraction, pressurized hot water extraction, negative pressure cavitation-assisted extraction, and pulsed electric fields have been used to assist the process (Meng and Lozano 2014). In general, the inedible portions of the fruits are removed from the edible portion and washed in distillated water. Then, fresh fruits can be previously dried and powdered or not. The aqueous extract is prepared homogenizing the fruit in distillated water, and it can be boiled (100 °C, 10 min) or not and then centrifuged to obtain the supernatant. The supernatant is usually cool, filtered, and freeze-dried prior to use. A technique of simultaneous steam distillation and solvent extraction in a Likens-Nickelson apparatus has been used to


determine the capsaicinoids content in a C. chinense Jack cultivar (Habanero) (Pino et al. 2007). Water, which is a very polar solvent, has a poor extraction capacity of capsaicinoids that are non-polar. This reduced effectiveness is accentuated in the case of t he less polar capsaicinoids such as dihydrocapsaicin, homocapsaicin, and homodihydrocapsaicin (Barbero et al. 2008). Distillation with water is, despite its low efficiency, the simplest form to obtain an essential oil. The essential oil forms an azeotropic mixture with water. Subsequently, after the condensation, they can be separated easily by decantation. The sample is exposed to temperatures close to 100 °C which can lead to changes in thermolabile compounds. Prolonged heating in contact with water can lead to hydrolysis of esters, polymerization of aldehydes, or decomposition of other components, reducing the quality in the final product (El Asbahani et al. 2015). As in almost all the extraction methods, the compounds extracted and the antioxidant activity obtained depend on the extraction time and the temperature (Stanojević et al. 2015; Sintim et al. 2015). When water distillation has been compared with other water extraction procedures, such as subcritical water extraction, results showed better extracting values with subcritical water (Gahungu et al. 2011). Due to extremely high temperatures, steam distillation under reduced pressure (0.0125 MPa) at 55 °C for 4 h has been successfully used to avoid production of artificial reaction flavor compounds (Jang et al. 2008) (Table 4). Pressurized hot water extraction (PHWE) is an attractive and environmentally friendly alternative for extraction since, at elevated temperatures, the viscosity and high surface tension of water decrease, while diffusivity and solubility of the capsaicinoids increase. However, the PHWE requires a sophisticated instrumentation since it needs an application of high pressures and temperatures (Bajer et al. 2015). However, this method has resulted more efficient to extract capsaicinoids than traditional Soxhlet extraction using methanol as solvent (Bajer et al. 2015). Maceration Mixing of a solvent and a solid matrix is one of the oldest and simplest technologies to transfer some compounds from a food matrix (in this case the fruit) to a solvent bulk. The plant extracts can be prepared directly from fresh fruit or from previously dried fruits. To avoid thermal degradation, maceration is carried out at room temperatures or under vacuum. The basic procedure consists of transferring the sample into the solvent for a long period, protected from light and with one daily agitation. The most common solvents used are methanol, ethanol, water or a mixture of them (Sasidharan et al. 2011; de Aguiar et al. 2015) although maceration with vegetable oils is increasing. More expensive methods such as homogenization with liquid nitrogen (Jang et al. 2008) and carbonic


maceration (Liu et al. 2014) have been used at experimental level. (Table 4). Generally, after maceration, the solid material dissolvent in the solvent phase is separated by filtration or centrifugation. Olive Oil Maceration The addition of aromatizers to the olive oil influences several characteristics and properties. Their inclusion improves olive oils sensorial characteristics, but concentration must be kept at low or moderate levels in terms of sensorial acceptability by consumers to avoid over-aromatization (Sousa et al. 2015). There is an increasing demand for top quality, healthy, and innovative food products. Consequently, flavored oils and oil macerated extract methodologies have been increasing developing. Flavored extra-virgin olive oil is the most aromatic oil commercialized. It could be done with essential oils, fruits, herbs, mushrooms, spices, and vegetables. These flavorings could be added to the olive oil before or after the oil extraction (Sousa et al. 2015). Cold pressing process, used to obtain extra-virgin olive oil, has been analyzed in two ways to flavor the final product: mixing the Capsicum seeds or fruits with olives before the pressing to obtain the flavored olive oil or by cold pressing of the Capsicum seeds. In the first case, the extraction is made of the mixture of olives and Capsicum powder and the yield and functional properties (as antioxidant) of this extraction is low (Baiano et al. 2009). In the second case, seeds are cold pressed alone to obtain the oil but the yield and the consumer acceptance are low for the high pungency of the oil (Yılmaz et al. 2015). The production of flavored oils by maceration for a long time period (between 1 and 3 months) in darkness and at room temperature is the most common technique to conserve the nutritional and bioactive quality of oils (Caporaso et al. 2013; Sousa et al. 2015; Ciafardini et al. 2006; Ciafardini et al. 2004) (see Table 4). In order to accelerate the olive oil aromatization, new techniques have been developed as the use of supercritical fluid extraction (SFE) with supercritical CO2 to extract oil from red fruits of Capsicum spp. The Capsicum oleoresin was then added to an extra-virgin olive oil and its oxidative stability was evaluated. Results showed that the Capsicum oleoresin produced by SFE can be used to produce stable flavored olive oils (Gouveia et al. 2006). Other accelerated methods such as ultrasound-assisted extraction (UAE) (10–20 % w/v, 20 min) and microwave-assisted extraction (MAE) (10–20 % w/v, 1– 60s) have been employed using 10–20 % of red chili powder. The content of capsaicinoids extracted by traditional infusion was higher than the non-conventional techniques. However, the production of flavored olive oils using technologies such as ultrasounds and microwaves could allow the production of high quality oils with an important time reduction (Paduano et al. 2014).


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Various experimental conditions to obtain Capsicum spp. oleoresins by non-conventional maceration

Maceration type

Common solvent used

Temperature (°C)

Pressure (MPa)

Time required

Reference

Solvent maceration

55 (steam distillation under reduced pressure)

0.0125 (steam distillation under reduced pressure)

4h (steam distillation under reduced pressure)

Jang et al. 2008

Solvent maceration

Liquid nitrogen to prevent the loss of volatiles (pretreatment) Deionized water (steam distillation under reduced pressure) Carbonic maceration

30

0.2000

30 h

Liu et al. 2014

Flavored olive oil

Olive oil

Room temperature

Room pressure

3 months

Sousa et al. 2015

Oil infusion

Olive oil

Room temperature

Room pressure

7–30 days

Caporaso et al. 2013; Paduano et al. 2014

Flavored olive oil

Olive oil

Room temperature

Room pressure

14 days

Ciafardini et al. 2004

Non-aqueous extracts

Corn, Sunflower and safflower oils

60–70-80

Room pressure

5–10 min

Guadarrama-Lezama et al. 2012

Extraction in vegetable oils

Mustard, sunflower, olive, coconut, palm, castor, neem, ground nut and gingelly oils

65

Room pressure

1h

Amruthraj 2014

Vegetable Oil Maceration The maceration of dehydrated Capsicum spp. in vegetable oils has been recently carried out using some comestibles (olive, corn, sunflower, safflower, coconut, and palm) and medicinal oils (mustard, neem, ricinums, ground nut, and ginger) at different temperatures and extraction times and then filtered and centrifuged to separate the solids to obtain the non-aqueous extracts of chili (Guadarrama-Lezama et al. 2012; Amruthraj 2014). The extraction of components from C. chinense (Bhut Jolokia) in different vegetable oils depends on the solubility of capsaicin and other compounds present in the oil, and it was also an efficient solvent to extract capsaicinoids for biological applications (Amruthraj 2014). Vegetable oil extracts of C. annuum L. showed high antioxidant activity without the use of organic solvents potentially harmful to the environment. Results depended on the extraction conditions and the refined vegetable oil employed so that, in general, lower temperatures resulted in higher antioxidant activity and the best vegetable oil was corn oil due to its particular fatty acids profile (Guadarrama-Lezama et al. 2012) (see Table 4). The use of ozonated oil has been developed with industrial purposes. However, this oil must not be consumed because the hazards related with ozone. Basically, the mixture with the vegetable oil and the chili powder is bubbled with oxygen gas and ozone until a grease with antimicrobial properties is obtained (Özyildiz et al. 2013). Cold Pressing Cold pressing is the most antique process to obtain oils consisting only in a mechanical pressing without heating.

This method has the advantage or little or no heat generation during the process giving good quality products that do not require refining but gives low yields (Reyes-Jurado et al. 2015). It has traditionally been employed to obtain virgin olive oil and in the last years to produce avocado oil and other oils seeds (Dos Santos et al. 2014; Febrianto and Yang 2011). In the case of essential oils, it has been traditionally used to extract essential oils from citrus fruits. During extraction, oil sacs break down and release volatile oils. Then the oil is removed mechanically by cold pressing yielding a watery emulsion. Oil is recovered by centrifugation (El Asbahani et al. 2015). Capia pepper seed oil was produced by a cold pressing technique; however, the extraction yield was very low compared with the traditional Soxhlet extraction with hexane and the resulted oil was not accepted by consumers (Yılmaz et al. 2015). Organic Solvent Extraction The plant material is macerated in an organic solvent; the extract is usually concentrated by removing the solvent under atmospheric or reduced pressure (El Asbahani et al. 2015). Many materials including oils, fats, and proteins are recovered from diverse biological sources by this type of extraction. The bioactive compounds in Capsicum fruits vary in chemical structure between cultivars; the solvent characteristics have a strong effect on the compounds present in the extract and their tested activity (Bae et al. 2012b) (see Table 5). Experimental data indicates that the concentration and activity of bioactive compounds in natural foods may be directly related to solvent properties such as lipophilic and hydrophilic solvents and their respectively polarity. Hence, lipophilic carotenoids are better extracted in non-polar solvents, such as

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0.654 0.762 1.000 Total Total Total 0.789 0.792 0.998 1.08 0.6 0.89 1.359 1.326 1.332 78 64 100 −114 −98 0 Ethanol Methanol Water

13 15 Would not flash

0.460 0.546 Total Total 0.782 0.785 0.38 2.1 1.342 1.377 81.6 82.6 −44 −89 Acetonitrile Isopropanol

6 11.7

0.228

0.309 0.355 1.30 Total

7.7 0.867

1.326 0.79 0.44 0.33

0.72 1.375

1.421 1.357 −95 −95 Methylene-chloride Acetone

−4 83

40 56

−84 Ethyl acetate

Would not flash −18

9.5 × 10−4 6.9 0.659 0.715 0.31 0.24 1.372 1.352 69 34.5 −95 −116 n-hexane Diethyl ether

−22 −45

Solubility in water at 25 °C (% w/w) Density at 25 °C (g/cm3) Absolute viscosity at 25 °C (cP) Refractive index at 25 °C Flash point at 0.1013 MPa (°C) Boiling point at 0.1013 MPa (°C) Melting point at 0.1013 MPa (°C) Solvent

Solvent characteristics and relative polarity of commonly used solvents in Capsicum spp. extraction. Adapted from Jouyban et al. 2011 and Reichardt 2004. Table 5

0.009 0.117

Food Bioprocess Technol (2017) 10:51–76 Relative polarity

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hexane, but flavonoids being hydrophilic are easily extracted in polar solvents as water (see Table 5). However, the antioxidant activity of each extract does not represent the total amount of bioactive compounds present in the whole fruit since the fruit has a wide variety of compounds with various polarities and they cannot be extracted totally by only one solvent (Bae et al. 2012b). There are many physical and chemical differences between the diverse biological materials. However, oils (edible and industrial) and other useful lipidic materials (vitamins, nutraceuticals, fatty acids, phytoesterols, etc.) can be extracted by mechanical pressing, solvent extracting, or a combination. The preparation of the material to be extracted differs, but generally cleaning and drying are steps required. For solvent extraction, the plant material is dissolved in a solvent to separate the oil from the insoluble meal. Many solvents have been evaluated for commercial extraction. In a typical chemical extraction process, solvents are used for dissolving reactants, solvating molecules, extracting products, and separating mixtures. However, the major part of the organic solvents currently found in industry is characterized by several dangerous effects for the human health and environment (Vian et al. 2014). The solvent extraction is the most commonly used technique to obtain oleoresins from Capsicum spp. usually used as color additive. The current European regulation (Commission regulation N° 231/2012) allows the use of ethyl acetate, methanol, ethanol, acetone, hexane, and isopropanol with a solvent residue of not more than 50 mg/kg individually or in combination and no more of 10 mg/Kg of solvent residue in dichloromethane. Meanwhile, FDA (2006) allows the use of acetone, ethanol, ethylene dichloride, hexane, isopropanol, methanol, methylene choride, and trichloroethylene. The extracted profile obtained depends on the solvent polarity and other physico-chemical properties of the particular solvent (see Table 5) and from the extraction conditions (time and temperature) (see Table 6). Therefore, less polar solvents as hexane, acetone, and methanol can extract carotenoids easily (Arimboor et al. 2015) and are less recommended to extract capasaicinoids than polar aprotic solvents such as acetone and acetonitrile and even for polar protic solvents such as methanol and ethanol (Amruthraj 2014). At high temperatures and long times, some reactions can occur and extraction rates of some compounds can decrease (El Asbahani et al. 2015). Solvent polarity could significant increase the extraction efficiency of specific lipophilic or hydrophilic compounds in different peppers as well as antioxidant activity. Hexane and methanol have a fairly narrow boiling point that makes them easy to recover (Yılmaz et al. 2015; Wang and Weller 2006). However, both are considered toxics for human health and for the environment and their presence in food is strictly regulated (with a maximum allowed of 290 ppm) (de Aguiar et al. 2013; Fernández-Ronco et al. 2013;

Author's personal copy

Dorantes et al. 2000 Conforti et al. 2007 Sasidharan et al. 2011 1:1 1:10 1:1 Room temperature Room temperature Depending the solvent used Maceration with shaking Maceration Maceration

15 min 144 h × 3 times 1h

Bae et al. 2012a, b 1:25 60 Soxhlet extraction

10 h

Chinn et al. 2011 De Aguiar et al. 2013 Fernández-Ronco et al. 2012 De Aguiar et al. 2014 1:6.6 1:30 1:1 1:30

Ethanol, acetone, acetonitrile Hexane Hexane, ethanol Hexane, ethanol, acetone and methanol Hexane, ethyl acetate, acetone, methanol, methanol/water (80:20, v/v) Isopropanol Methanol Methanol, ethanol, or mixture of alcohol and water

Maceration with shaking Soxhlet extraction Maceration Maceration

1h 6h 48–72 h 6h

Dong et al. 2014 1:10 followed by 1:4

40–50 % ethanol at room temperature 95 % ethanol at 90 °C 50 69 25–65 Until boiling Two stages extraction

30 min followed by 120 min

Gao et al. 2005 Menichini et al. 2009 1:10 Not specified 70 Not specified Maceration Maceration

Ethanol (70 %) Ethanol n-Hexane Methanol Ethanol

Temperature (°C) Extraction type

30 min Not specified

61

Solvent used

Table 6

Some experimental conditions to obtain Capsicum spp. oleoresins by organic solvent extraction

Time required

Sample (g)/solvent (mL) ratio

Reference


Menchini et al. 2009). Other organic solvents used to obtain Capsicum oleoresins are acetone, acetonitrile, isopropanol, and ethanol (Table 6) (Dorantes et al. 2000; Chinn et al. 2011; de Aguiar et al. 2014). However, besides the organic solvent used, the capsaicinoids yield depends on the part of the fruit examined. There are few solvents that can be used directly to obtain carotenoids and capsaicinoids from fresh fruits (high moisture samples). These solvents should be hydrophilic such as methanol, ethanol, and acetone (Dong et al. 2014). Nowadays, the use of non-polluting and non-toxic solvents is imperative in most countries, so solvent byproducts from petroleum are being substituted from less toxic alternatives, such as ethanol, particularly in products for human consumption (Arimboor et al. 2015). Hence, a Japanese research of the organic solvent residues levels from 145 food additives, 23 health food materials, and 19 commercial health food products found that ethanol was the dominant commercial solvent followed by methanol, acetone, isopropanol, and ethyl acetate. In this study, three samples of commercial paprika oleoresin were analyzed showing that two of them were extracted with ethanol and one with methanol (Uematsu et al. 2008). N-Hexane is the most traditional solvent for oil extraction (Table 6). It is a non-polar solvent mostly used for the extraction of vegetable oils. Hexane has a fairly narrow boiling point range of approximately 63–65 °C, and it is an excellent oil solvent in terms of oil solubility and ease of recovery and recycling. However, acute inhalation exposure of humans to high levels of hexane causes mild central nervous system effects and chronic exposure is associated with polyneuropathology (Wang and Weller 2006). Hexane leads to the extraction of dyes and substances (carotenoids) in Capsicum oleoresins and shows higher extraction yield than ethanol in some studies of conventional solvent extraction due to the low relatively polarity of the solvent (Fernández-Ronco et al. 2013). Typically, dried red Capsicum is extracted as a mash in a large heated volume of n-hexane; the extracted liquid is recovered and the hexane is evaporated or distilled from the sample leaving an oleoresin and recovering the solvent. However, capsaicinoids are partially soluble in hexane. For this to obtain non-pungent Capsicum oleoresins, only mild or non-pungent fruits can be used (Richins et al. 2010). Finally, conventional extraction with n-hexane is used as a solvent in non-conventional methods such as MAE (Williams et al. 2004), UAE (Fernández-Ronco et al. 2013) and SFE (Duarte et al. 2004), although with less favorable results to extract capsacinoids in comparison with other more polar solvents such as acetone. Acetone and methanol are used both to extract carotenoids (Hornero-Méndez and Mínguez-Mosquera 2001) and capsaicinoids (Amaya-Guerra et al. 1997; Amruthraj 2014) for their medium relative polarity. However, at


industrial level, these solvents are not commonly used because their toxicity and flammability. Acetone is considered the best polar aprotic solvent for the efficient extraction of capsaicinoids for pharmacological and biological purposes (Amruthraj 2014). Acetonitrile is not allowed in foods, but it has been used to extract capsaicinoids and carotenoids for scientific purposes (de Aguiar et al. 2013; Al Othman et al. 2011; Arimboor et al. 2015). Isopropanol was used to obtain lipidic extracts of Capsicum with antimicrobial properties (Dorantes et al. 2000). It has also been used combined with n-hexane to determine tocopherols in Capsicum spp. a (Abbeddou et al. 2013) and capsaicinoids by HPLC (Caporaso et al. 2013) and with methanol–water to determine carotenoids (Daood et al. 2002). Finally, ethanol is the most used organic solvent in the food industry because of their low toxicity both to humans and environment (Singh et al. 2014). Although the extraction yield of carotenoids is not higher, some authors have reported a good extraction yield of capsaicinoids with ethanol/water mixtures both in maceration (Amaya-Guerra et al. 1997; Al Othman et al. 2011) and Soxhlet extraction (de Aguiar et al. 2014). However, to extract color pigments (carotenoids), other solvents such as acetone (Chinn et al. 2011) or hexane (Fernandez Ronco et al. 2012) provided oleoresins with better color quality. Because of their low toxicity, ethanol has been widely researched as an organic solvent in Capsicum extractions. Therefore, despite not having the best extraction yield, it has been optimized in many researches. Therefore, Gao et al. 2005 tried to optimize the process of extracting capsaicinoids in C. annuum L. with a mixture of 70 % ethanol/water at 70 °C, 0.5 h and a stock ratio 1:10 (mass/volume) in a three-step extraction. Different ethanol/water solutions have been used to extract selectively carotenoids and capsaicinoids in dried hot Capsicum spp. (Santamaría et al. 2000) and fresh hot red Capsicum (Dong et al. 2014) with great yield rates. Most of the solvents are employed to extract from previously dried fruits in order to avoid the water oxidation and to improve the solubilization of the lipophilic substances. However, there is interest in the development of extraction methods with fresh fruits in order to reduce the total costs of the process and to improve the colorant capacity since carotenoids may be partially destroyed during the drying process. The first step with a 40–50 % ethanol in fresh fruits (with high water content) was used to extract most of capsacinoids and the second step with 95 % of ethanol was used to extract carotenoids by Dong et al. 2014. In the case of dried Capsicum (Santamaría et al. 2000), the extraction of capsaicinoids was performed with a 30 % ethanol solution followed by a carotenoids extraction with a 96 % ethanol solution.


Emergent Technologies for Extraction There is an increasing demand for new extraction techniques with the properties of amenable to automation, shortened extraction time, and reduced organic solvent consumption which not only prevents pollution but also reduces sample preparation costs. (Yu et al. 2009). Between them, microwaveassisted extraction (MAE), ultrasound-assisted extraction (UEA), and supercritical fluid extraction (SFE) are the most important technologies developed during the last years. Microwave-Assisted Extraction MAE is mostly used to extract water from the particles to dry them or as a pretreatment before or at the same time that conventional dehydration processes. For example, it is commonly used in combination with air-drying system during drying increasing the drying rate of the final product and the quality of the dried product obtained (Arslan and Özcan 2011; Swain et al. 2012). However, MAE efficiency and selectivity depend significantly on the dielectric constant of the extraction solvent mixture, namely its chemical polarity that defines the compounds extracted (Csiktusnádi Kiss et al. 2000). The MAE process allows higher recovery of analytes and reproducibility than conventional techniques. Also, it is an easy to use and relatively low-cost technology (Yu et al. 2009). Many MAE techniques have been developmental for natural products such as open system microwave heating with water or organic solvents, compressed air microwave distillation, vacuum microwave hydrodistillation, solvent-free microwave extraction, and microwave hydrodiffusion and gravity (Mason et al. 2011). However, in Capsicum spp. extraction, the most used technique is the MAE extracted with hexane as organic solvent where the fruit is immersed in a non-absorbing microwave solvent such as hexane and irradiated by microwave energy (Gogus et al. 2015). Here, the MAE is an alternative extraction method because of their considerable saving in processing time, solvent consumption, and energy having a high extraction rate of volatile compound in Capsicum spp. compared with other traditional techniques and even with MAE extracted with water as solvent, probably because the low solubility of volatile compounds (Gogus et al. 2015). However, the severe thermal stress and localized high pressures produced during MAE cause the cell rupture more rapidly than in conventional extraction. Because of that, it is convenient that volatile oils are dissolved in the organic solvent before being separated by liquid–liquid extraction (Mason et al. 2011; Gogus et al. 2015). Normally, the sample (between 1 and 10 g) is immersed in non-microwave absorbing solvent (such as hexane) for 3–30 min, and then microwaves are applied into a low volume of solvent (aprox. 40 mL). To avoid these drawbacks, recently, microwave-


vacuum drying and far infrared-assisted microwave vacuum that are a free solvent extractions have been successfully used for drying red Capsicum spp., but not to extract its components. In MAE extraction, no degradation of capsaicinoids from fresh samples of Capsicum spp., at laboratory level, was observed up to 150 °C being a faster method compared with traditional ones and the better parameters to extract capsaicinoids have been the following: 125 °C, 500 W, 25 mL of 100 % of ethanol as solvent, 0.5 g of triturated fresh fruits, and 5 min of extraction time (Barbero et al. 2006). Similar results were obtained using acetone at 30 % where the extraction time was considerably reduced (Williams et al. 2004). However, in a research to extract capsaicin from C. frutescens with different methods, MAE showed a lower extraction recovery probably because the lack of proper stirring of the solvent during the extraction process (Nazari et al. 2007). Microwave vacuum drying was initially developed to increase the extraction yield of oxidable components such as antioxidants, which are important bioactive compounds in Capsicum spp. in this technology, the extraction can be performed at lower temperature and the air in the extraction system is mostly pumped out, so the oxidation is avoided or reduced since there is little oxygen in the process of extraction (Yu et al. 2009). Far infrared could be used as an additional energy source to assist microwave-vacuum drying improving the drying rate and giving a better quality product with lower changes of all color parameters, shrinkage coefficient, and hardness while rehydration ability was found higher. Consequently, the optimum condition for drying Capsicum spp. was a microwave power of 300 W under absolute pressure of 21.33 kPa with the applied far-Infrared power of 300 W (Saengrayap et al. 2015). Finally, osmotic dehydration has been successfully used as a pretreatment before MAE for faster drying, thereby maintaining final product quality (Swain et al. 2012). Ultrasound-Assisted Extraction Ultrasounds can enhance the extraction process by increasing the mass transfer between the solvent and plant material. In addition, the collapse or cavitation bubbles leads to better cell disruption via the formation of microjets due to asymmetrical bubble collapse near a solid surface. This allows for improved solvent penetration into the plant body and can also break down cell walls (Mason et al. 2011). The method is inexpensive, simple, and an efficient alternative to conventional extraction techniques that increase the extraction yield, reduce the process time and the operating temperature, and even increase the quality of the extract (Wang and Weller 2006). However, these benefits depend on the nature of the plant matrix. In hot varieties of C.annuum and C. chinense, UAE has been successfully used to extract capsaicinoids using methanol as solvent at relatively low temperatures (50 °C)

63

and short time (10–15 min) and 360 W of power (Barbero et al. 2014; Barbero et al. 2008; Sganzerla et al. 2014). Ethanol (a much less toxic solvent) has also been used to extract capsaicinoids from dried C. frutescens on a pilot scale, but the yield extraction was lower than the obtained from traditional industrial scale maceration with organic solvents. However, the results showed that the potential use of UAE could shorten the extraction time and lower the operating temperature which resulted in lower operation costs (Boonkird et al. 2008). This method has been successfully used to extract colorants from Capsicum spp. varieties obtained a high concentration in caroteonids using hexane and ethanol as solvents in contrast to the classical process of maceration using the same solvents mostly because the extraction time was reduced (FernándezRonco et al. 2013). Supercritical Fluid Extraction SFE has been applied as an alternative to traditional methods for the extraction and fractionation of active compounds, mainly lipid compounds from natural matrices. Carbon dioxide is the most common supercritical fluid employed. It behaves a critical temperature of 31.35 °C and critical pressure of 7.39 MPa expanding to fill its container like a gas but with a density like that of a liquid. It is an appropriate solvent for the extraction of bioactive compounds from biological substrates due to its low cost, non-toxicity, non-flammability, inertness, and good extraction capacity although limited to dissolve compounds with high molecular weight, regardless of their polarity such as carotenoids. Indeed, the critical properties of CO2 are moderated when compared with other green solvents allowing SFE to be carried out with low-cost energy for pressurization and temperatures that do not damage the target compounds (Santos et al. 2015; Araus et al. 2012). The obtained extracts in red C. annuum L. vary from orange, light red, to intense dark red, depending on process conditions, and have several advantages over extracts conventionally obtained with organic solvents because they do not have residues of toxic solvents and it is possible to vary the content of capsacinoids and carotenoids by changing the extraction parameters (Perva-Uzunalić et al. 2004). Extraction using CO2 is generally carried out with two-stage separation of extracts into a pungent oleoresin and an essential oil fraction. The extract is viscous, pasty, and semisolid and thus difficult to recover from separation vessels (Catchpole et al. 2003). The main disadvantage of this technology in comparison to the conventional methods is the high investment requirements related to the high pressure operation, although results have demonstrated the economic feasibility of the process to obtain bioactive compounds from Capsicum oleoresin (Fernández-Ronco et al. 2013). The development of commercial SFE systems requires the economical evaluation of the process at different


levels. At the initial stage, the cost of equipment and cost of fabrication can be approximate but needs to make into account both the capacity and the inflation in a detailed way. In the case of C. chinense (Habanero) oleoresins is possible to obtain oleoresins free of organic solvents that may be used for human consumption without risk. Moreover, the difference between the manufacturing cost and the probably selling price presents a good perspective for industrial application (Rocha-Uribe et al. 2014). The particle size, moisture content, and oil content affect the SFE. A decrease in particle size increases the extraction efficiency and moisture levels higher than 18 % decrease the efficiency (Nagy and Simándi 2008). Fractionation of spice extracts with SFE using CO2 as solvent using 2, 3, or 4 separator vessels at different pressures and temperatures to obtain fractions with different characteristics has been reported (Jarén-Galán et al. 1999). These authors found that, in the case of hot fruits, an orange-yellow pungent tasting extract containing capsaicin and few carotenoids was extracted in the first stages at lower pressures. However, in the second stages, at higher pressures, a darkness extract containing carotenoids and fatty acid was obtained. In sweet fruits, approximately 62 % of total carotenoids in raw material was recovered in the extract, and the rest remained occluded in the heat exchanger (Ambrogi et al. 2002). For the analysis of short and long chain free fatty acids from seeds of Capsicum spp., SFE with supercritical CO2 using ethanol as co-solvent was successfully employed (Li et al. 2011). Only few researches have been reported using others extraction fluids, such as sub-critical propane and dimethyl ether. Propane is cost-effective alternative to SFE using CO2 due to the lower operating pressures and lower energy consumption required. Dimethyl ether has similar advantages to propane (Catchpole et al. 2003). Results showed that subcritical dimethyl ether was as effective at extracting the pungent principles as supercritical carbon dioxide, although a substantial amount of water was also extracted. However, subcritical propane was less effective, obtaining a half yield of capsaicinoids than supercritical CO2 and subcritical dimethyl ether (Daood et al. 2002; Catchpole et al. 2003). The yield of paprika extracts (C. annuum L.) was found fairly constant with subcritical propane at different conditions and resulted superior than CO2 to extract carotenoids and thocopherols (Gnayfeed et al. 2001). However, the partial extraction of pungent compounds with subcritical propane may be useful for the production of oleoresin with slight pungency and high color intensity. Subcritical propane may be useful to extract fatty acids, tocopherols and carotenoids (Gnayfeed et al. 2001). SFE with CO2 has been used to extract both carotenoids and capsaicinoids from varieties of C. annum, C. frutescens, and C. chinense under different process conditions. In general, Capsicum oleoresins are mainly composed by lipid matter,


carotenoids, and capsaicinoids. Between carotenoids, capsorubin, capsainthin, zeaxanthin, β-cryptoxanthyn are mainly responsible from the red color while β-carotene acts mainly as an antioxidant. Most commercial valued oleoresins are those that present at high red coloring capacity that is caused by carotenoids pigment with or without pungent flavor due to the presence of absence of capsaicinoids (FernándezRonco et al. 2011). In few cases, tocopherols have been analyzed (Abbeddou et al. 2013). Capsicum oleoresin has one of the highest carotenoids pigment concentration of products derived from natural sources. The use of supercritical CO2 reduces the isomerization and decomposition of carotenoids and increases the extraction yield because of the low polarity of these compounds (Barros et al. 2015). In non-pungent varieties of C. annuum L., the highest extraction yield was found at 60 °C, 24 MPa, and 12 min and with 0.2–5 mm of particle size. Applying these conditions, the extraction yield was 97.0 and 68.1 % for tocopherols and carotenoids, respectively (Romo-Hualde et al. 2012). In pre-pelletized Jalapeño peppers (C. annuum L.), the flakes were conditioned to low moisture, ground finely, and pelletized at high pressure before the SFE using CO2 as solvent. The oleoresin obtained after 4 h at 40 °C and 12 MPa resulted in a light yellow tinge (del Valle et al. 2003). A fractioned extraction has been used in other non-pungent C. annuum L. varieties using 1 % of ethanol or acetone as cosolvent to obtain highest red pigment yields. During the fractioned extraction, in the first step, at low pressure, the compound extracted is almost exclusively β-carotene while in the second stage, at high pressure, carotenoids responsible from red color (capsorubin, capsanthin, zeaxanthin, and βcryptoxanthyn) were mainly obtained (Jarén-Galán et al. 1999). Ethanol as co-modifier and tapping solvent has also used in hot Capsicum varieties allowing the inclusion of a differential precipitation step without extract of chlorophyll pigments that may present as contaminants in dried fruit samples (Richins et al. 2010). Recently, avocado oil has been used as co-solvent in simultaneous extraction using SFE to extract capsainthin from C. annuum L. with a clean technology. For that, freeze-dried avocado and Capsicum fruits were separately packaged in a single-bed extractor in which supercritical CO2 was passed through the bed at 50 °C and 40 MPa. The target compounds were simultaneously extracted from both sources extracted giving intensely red-colored oil containing 280–460 μg/g capsanthin with an extraction yield of around 30–50 % of capsanthin was extracted (Barros et al. 2015). The extraction of capsainthin has been successfully improved with the use of triolein-entrained SFE with CO2 as solvent because the triolein increases the solubility of capsanthin independent on system temperature and pressure because of their nonpolar interactions between the 18-C fatty acid chains in triolein and the 22-C nonpolar core of carotenoids (Araus et al. 2012).


Capsaicinoids has been extracted both in hot C. annuum L., C. chinense, C. baccatum, and C. frutescens varieties. In the case of red hot C. annuum L. with high pressure apparatus using near and supercritical CO2 results showed that the highest yield of oil and capsaicin content was found at 60 °C and 35 MPa (Kwon et al. 2011). Moreover, at lab level, SFE with supercritical CO2 has been used to extract capsacinoids with a wide concentration range (Peusch et al. 1997; Sato et al. 1999). In C. frutescens SFE with supercritical CO2 as solvent, high extraction yields in oleoresins and capsaicinoids were obtained at pressures around 20–22 MPa. The extract obtained gave similar pungency virgin olive oil than commercial flavored olive oils without modification of the original oil color (Duarte et al. 2004). In native Brazilian Capsicum spp., the highest concentration of capsaicinoids was found in C. frutescens. Using supercritical carbon dioxide, the highest concentration was found at the lower pressures, indicating that it may be a competition between capsaicinoids and other soluble compounds for supercritical CO2 at higher pressures being the best extraction conditions 15 MPa and 40 °C. Moreover, the extraction kinetics of capsaicinoids showed that these substances are extracted in the first minutes of extraction, when mass transfer rate is high (de Aguiar et al. 2013). Recently, SFE has been successfully assisted by ultrasounds to extract capsaicinoids from C. frutescens L. using CO2 as solvent increasing the global yield of the oleoresin up to 30 % when compared to SFE without changing the total capsaicinoids and phenolics profile. The best operating conditions resulted 360 W for 60 min and 40 °C, 15 MPa, and 1.673 × 10−4 kg/s (Santos et al. 2015). Moreover, the highest extraction rates were obtained for high CO2 flow rates, low particle diameter, and low extraction bed volume. These results could be explained by the high importance of the convective phenomenon under these conditions (Silva and Martínez 2014). The extraction of capsinoids with SFE using supercritical CO2 has been studied in sweet C. chinense where high capsaicinoids and low capsaicinoids concentrations are naturally presents. SFE process with CO2 resulted in low extraction yields when compared to solvent extraction with methanol and acetone. However, the extract obtained with the lowest CO2 density had a high concentration of capsinoids, suggesting that the SFE using CO2 without co-solvent process can be used to obtain concentrated extract of these extracts for further application in food and pharmaceutical industry (de Aguiar et al. 2014). Pelletization can increase the volumetric yield of SFE with supercritical CO2 at 40 °C and 32 MPa, in green C. annuum L. (jalapeño). Sample compactation by pelletization appeared to be slightly less effective when using flakes than ground material, independent on the initial sample moisture. A reduction in the particle size of the pellets improved the mass transfer

65

but caused a reduction in packing density, and these two factors had opposite effects on the volumetric yield of the process (mass of recovered solute per unit time and per unit volume of extraction vessel), which was also affected by prepelletizing sample conditioning. (Uquiche et al. 2005). Others Application of high intensity pulsed electric field (PEF), a low thermal short time process induces membrane permeabilization in various biological cell systems due to electrical breakdown of the membrane. The resultant membrane permeabilization affects heat and mass transfer processes in subsequent unit operations such as extraction with improved quality of the extracted juices. In C. annum L. (paprika), an extraction yield about 91 % and good quality of juice was obtained from the fruit mass after a pretreatment with electric pulsed electric fields followed by pressing at 10 MPa (Ade-Omowaye et al. 2001). As a drying pretreatment, PEF was applied to C. annuum L. with electric field strength of 1.0–2.5 kV/ cm using a fixed pulse width of 30 μs and at a pulse frequency of 100 Hz. The pretreatment resulted in cell membrane disruption without visible changes in the surface structure of the fruit. The reduction in drying time by PEF pretreatment was beneficial to color quality of dried red pepper (Won et al. 2014). Pressurized liquid extraction (PLE) is a relatively novel extraction method in which temperature and pressure are utilized to accelerate the extraction of compounds originated from solid or semisolid samples. The application of high temperature and high pressures modifies the physical properties of the extraction solvents, with the effect of increasing selectivity in the extraction working above the boiling point of the solvent and enhances the extraction efficiency because it decreases the viscosity of the solvent, allowing a better penetration of solvent molecules into the sample matrix. PLE uses less organic solvent, and the extraction time is reduced compared with traditional techniques. However, the equipment is highly expensive due to its precision. In addition, PLE can be performed in the absence of oxygen and light which reduce the oxidative degradation of sensible compounds such as antioxidants (Liu et al. 2014; Barbero et al. 2006). PEL has been used with water, ethanol, or methanol (0–20 % in water) to extract capsaicinoids in C. annuum varieties of different pungency showing that methanol was the best extraction solvent (Barbero et al. 2006). Finally, PEL has method has been optimized with methanol as solvent at 100 °C and 10.3 MPa to extract capsaicinoids from a dried C. annuum cultivar (Liu et al. 2014). However, methanol is not a good solvent for the food and pharmaceutical industry for its high toxicity and flammability (Jin et al. 2004).


Bioactivity Health Benefits from Capsicum spp. Capsicum spp. are one of the most consumed vegetables worldwide, mainly due to the diversity of culinary purposes and its handling plasticity. The consumption of both fresh and dry as spice seems to have positive effects on human health (Tundis et al. 2011). From a nutritional point of view, Capsicum spp. fruits are generally considered good sources of most essential nutrients. They are rich in antioxidants, colors, flavor, and vitamins such as vitamins E, A, C, and B complex. The quality of the fruit depends on its chemical composition. Among most important factors that affect composition, environmental and growth conditions, variety, ripeness, maturity, and handling can be found (Martínez et al. 2007). The total soluble solid content and acidity increases during ripening. The fat, ash, and protein contents are generally higher in red pepper than in green peppers (see Table 1). In the case of Arnoia peppers (C. annuum L. var. annuum cv. Arnoia), potassium was the most abundant mineral both in green (2.80 g/100 g) and red peppers (251 g/100 g) (Martínez et al. 2007). Moreover, the quantity and composition of bioactive compounds found in Capsicum spp. depends from the extraction method and solvent used in its extraction (see Table 7). This results in a difficult accurately measure of bioactive metabolites in different Capsicum varieties. Thus, besides being used fresh or uncooked in many diets, fruits are subjected to several industrial transformations to convert them to preserves, condiments, species, etc. Much of the nutraceutical value resides in their low calorie content and high antioxidant levels, especially ascorbic acid (vitamin C) and β-carotene (provitamin A). In fact, fruits are one of the agricultural products with the highest ascorbate content. One hundred grams of Capsicum fruits provide approximately 25 % of the recommended daily amount of vitamin A, and 50 g of fresh fruit is enough to exceed the daily recommendation for vitamin C (Palma et al. 2015; Guil-Guerrero et al. 2006). Moreover, in the case of Jalapeño (C. annuum L.), the profiles of antioxidant capacity were completely different for green and red peppers and were more abundant in red fruits. Chlorophyll a (67.71 μg/g) and free all-trans-lutein (4.39 μg/g) were the major pigments in raw green peppers, whereas free all-trans-capsanthin (37.60 μg/g) was the most abundant in raw red pepper. The heat treatment generated at least 12 compounds, mainly pheophytins and cis isomers of carotenoids and reduced the fruits antioxidant capacity (Cervantes-Paz et al. 2012). Capsicum fruits exhibit a high antioxidant activity due to a wide variety of compounds such as phenols, flavonoids, capsaicinoids, and carotenoids. A strong correlation between the presence of bioactive compounds in Capsicum spp. and their antioxidant activity evaluated by means of DPPH


radical-scavenging (Bae et al. 2012a, b), and ABTS (Xin et al. 2014) has been found in some studies, but not in others (Rahiman et al. 2013). This strong antioxidant activity plays an important role in the prevention of cardiovascular diseases, cancer, and neurological disorders. However, the content and biodisponibility depend on the fruit ripening stage and the post-harvesting process, so freezing and boiling process negatively influenced the content of these active compounds (Loizzo et al. 2015). Water extracts from hot fruits of C. annuum L. (Tepin) and C. chinense (Habanero) have prevented ferrous lipid peroxidation in rat’s brain. However, Tepin fruits are more potent inhibitors than Habanero fruits; meanwhile, unripe Tepin showed the highest protective ability due to its higher total phenolic content and ferrous chelating activity; furthermore, while ripening decreased the antioxidant properties in Tepin, it showed a reversed effect in Habanero increasing its antioxidant capacity (Oboh et al. 2007). The consumption of C. frutensces (cayenne pepper) and their mixtures with garlic and ginger may help to modulate oxidative stress caused by hypercholesterolemia in rats (Otunola et al. 2010). Hot pepper such as Jalapeño, Scotch Bonnet, and Bhut Jolokia showed identical non-pungent water-soluble components similar to sweet peppers, regardless of their pungency level. This is probably due to the biosynthetic origin of most of these compounds in the chloroplast. Moreover, hot chili contained other anti-inflammatory compounds than capsaicinoids (Liu et al. 2009).

Antioxidant Activity Antioxidant Compounds in Capsicum spp. As previously mentioned above, Capsicum spp. are known to be a good source of different phytochemicals including vitamins A and C, phenolic compounds, flavonoids and carotenoids, among others. More than 125 volatile compounds have been identified in fresh and processed Capsicum fruits, although the significance of these compounds for the aroma is not yet well known (El-Ghorab et al. 2013). Hot Capsicum varieties are the only plants that are able to produce capsaicinoids, responsible for their characteristic hot taste. The concentration of these compounds depends on cultivar, maturity stage, growing conditions, and postharvest manipulation. In this way, the concentration of phenols varied from 745 to 1032 mg/100 g, flavonoids from 201 to 389 mg/100 g, and ascorbic acid from 694 to 2153 mg/100 g in some jalapeño and Serrano cultivars (Alvarez-Parrilla et al. 2011). Some hot C. annuum L. (Jalapeño and Serrano), both fresh and processed, are good sources of antioxidants such as phenolics and ascorbic acid (Alvarez-Parrilla et al. 2011). Moreover, these two varieties showed a lipid-protective effect


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Bioactive products from Capsicum spp. extracted with different solvents and extraction methods

Solvent used

Extraction methods

Bioactive compound extracted

Reference

None

Cold pressing

Capsaicinoids

Yılmaz et al. 2015

Acetone + Ethanol/water (9:1) Ethanol/Water

Fractioned extraction

Amaya-Guerra et al. 1997

Al Othman et al. 2011

Acetonitrile

HPLC

Capsaicinoids Carotenoids Carotenoids Capsaicinoids Capsaicin and Dihydrocapsaicin

Isopropanol + methanol/water

HPLC

Carotenoids

Daood et al. 2002

Fractioned extraction

Santamaría et al. 2000; Dong et al. 2014

Isopropanol + n-hexane

HPLC

Tocopherols

Abbeddou et al. 2013

Acetone

Maceration

Carotenoids

Hornero-Méndez and Mínguez-Mosquera 2001

Acetonitrile

Maceration

Capsaicinoids

Chinn et al. 2011

Comestible and medicinal oil

Maceration

Capsaicionoids

Amruthraj 2014

Ethanol

Maceration

Capsaicinoids

De Aguiar et al. 2014

Ethanol/Water

Maceration

Capsaicinoids

Gao et al. 2005

Isopropanol

Maceration

Capsaicinoids

Dorantes et al. 2000

n-Hexane

Maceration

Capsaicinoids

Fernández-Ronco et al. 2013; Richins et al. 2010

Olive oil

Maceration

Capsaicinoids

Paduano et al. 2014

Refined vegetable oil

Maceration

Carotenoids

Guadarrama-Lezama et al. 2012

Water

Maceration

Capsaicinoids

Pino et al. 2007

Acetone

MAE

Capsaicinoids

Williams et al. 2004

Ethanol

MAE

Capsaicinoids

Barbero et al. 2006

Methanol

PLE

Capsaicinoids

Liu et al. 2014; Barbero et al. 2006

Water

PHWE

Capsaicinoids

Bajer et al. 2015

CO2

SFE

Perva-Uzunalić et al. 2004

CO2 + dimethyl ether

SFE

Carotenoids Capsaicinoids Carotenoids

Catchpole et al. 2003

CO2

SFE

Carotenoids

Barros et al. 2015

CO2

SFE

Capsaicinoids

Kwon et al. 2011; Peusch et al. 1997; Sato et al. 1993; Duarte et al. 2004; de Aguiar et al. 2013; de Aguiar et al. 2014

CO2 + ethanol

SFE

Ambrogi et al. 2002; Li et al. 2011

Propane

SFE

CO2

SFE + UAE

n-Hexane

Soxhlet

Carotenoids Free fatty acids Carotenoids Tocopherols Free fatty acids Capsaicinoids Phenols Capsaicinoids

Ethanol

UAE

Capsaicinoids

Gnayfeed et al. 2001; Romo-Hualde et al. 2012 Santos et al. 2015 Fernández-Ronco et al. 2013; Richins et al. 2010 Boonkird et al. 2008

Hexane–methanol

UAE

Carotenoids

Fernández-Ronco et al. 2013

Methanol

UAE

Capsaicinoids

Barbero et al. 2014 Sganzerla et al. 2014

MAE microwave-assisted extraction, PLE pressurized liquid extraction, PHWE pressurized hot water extraction, SFE supercritical fluid extraction, UAE ultrasound-assisted extraction

mainly due to the presence of the phenolic compounds (Alvarez-Parrilla et al. 2012).

Capsaicinoids which consist on capsaicin, dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, and homocap


saicin can exert multiple pharmacological and physiological effects. They are biosynthesized by condensation of fatty acids and vanillyllamine, and the placenta of the fruit is the major site for their biosynthesis. Capsaicinoids are stable in both polar and nonpolar solvents and produce the sensation of burning in the body when comes into contact (Luo et al. 2011). In plants, capsaicin purportedly plays a role in preventing microbial infections and suppressing unsuitable infestations as well as being a deterrent to depredators (Singletary 2011). In human health, it has demonstrated benefits as a topical pharmaceutical to mitigate pain and other neurological conditions. However, the capacity of dietary capsaicin to manage gastrointestinal distress is unclear, due to the lack of understanding its apparent contradictory actions within various segments of the gastrointestinal tract. Capsaicin’s pungency has limited its use in clinical trials to support its biological activity (Reyes-Escogido et al. 2011). In the last years, a lot of data has been published about linking capsaicin and hot Capsicum spp. to improve weight loss and weight maintenance as a promising alternative, as well as leasing glucose intolerance and insulin resistance. (Sharma et al. 2015; Singletary 2011). Consumed worldwide, the capsaicin present in hot Capsicum spp. has a long story of controversy about whether its safety. However, the US Food and Drug Administration considered that the Capsicum fruits are completely safe, but not pure capsaicin that it is considered not totally safe. High consumptions of hot fruits may be a risk factor for gastric cancer, but this is not entirely demonstrated (Bode and Dong 2011). Capsinoids are less pungent than its analogs of capsaicinoids found in some sweet cultivars of Capsicum spp. They consist mainly on capsiate, dihydrocapsiate, and nordihydrocapsiate, presenting a similar structure as capsaicinoids. In the last years, capsinoids have been related with a strong thermogenic activity and visceral fat burning and also have been successfully used to control weight management without the inconvenient of capsaicinoids consumption. The health benefits of non-pungent components from Capsicum spp. such as carotenoids have been poorly explored. Carotenoids are responsible for the yellow-orangered color of Capsicum spp. and are composed by more than 50 identified structures being the most important β-carotene, α-carotene, capsanthin, capsorubin, crytpocapsin, αcryptoxanthin, β-cryptoxanthin, lutein, antheraxanthin, violxanthin, and zeaxanthin (Giuffrida et al. 2013). These pigments are commonly found in photosynthetic plants, algae, and microorganisms and play an important role in protecting tissues from light and oxygen. β-Carotene, α-carotene, and βcryptoxanthin are important sources of provitamin A. Carotenoids bearing a k-ring as end group have been shown to have strong reactive oxygen scavenging potential and an inverse relationship between human chronic disease incidents and intake of carotenoids has been found. Other health


benefits such as cancer prevention and eye protection have also been described (Arimboor et al. 2015; Abdel-Aal et al. 2013). Capsanthin, which is the major carotenoid present in Capsicum spp., is present in an acylated form with fatty acids. This carotenoid does not possess provitamin A activity but has been shown to be effective as a free radical scavenger. It has been proved that it has a plasma HDL cholesterol raising effect in plasma (Aizawa and Inakuma 2009). Phenolic compounds are found in considerable quantities in many fruits and vegetables and thus form an integral part of the human diet. Their consumption is related with reduced risk of cardiovascular diseases and certain types of cancer. In C. baccatum L. var. pendulum, the antioxidant activity was positively correlated with the amount of phenolics found in each sample (Kappel et al. 2008). In C. annuum L. cultivars, the phenolic content depended strongly on the cultivar, maturity stage, part of the fruit analyzed, and the drying process, freeze drying being the most conservative method although the loss of phenolics could be higher than 50 % (Materska 2014). As previously said, all Capsicum spp. are a rich source of an extensive diversity of bioactive compounds with potential health benefits. However, the bioactivity depends on the maturity stage, the specific variety of Capsicum spp., and the extraction method (Conforti et al. 2007; Gahungu et al. 2011; Jang et al. 2008; Aliakbarlu et al. 2014). Antioxidant Activity in Different Extracts Capsicum spp. hydrophilic fraction represents the main contribution to the total antioxidant activity of the fruits and mainly depends on the cultivar and maturity stage of the fruit. Although small differences in the lipophilic fraction have been found under different cropping systems (organic or conventional) and the growth medium (soil or soilless) showing higher lipophilic antioxidant content under organic conditions (López et al. 2014). The composition of lipophilic compounds and the phenol profile varies during the different stages of ripening in C. annuum fruits modifying the antioxidant activity. The radical scavenging activity increases with increasing of phenolic content for green and red chili extracts. Red pepper fruits had potent antioxidant property (~450 CI μg/mL DPPH) (Conforti et al. 2007). In general, there is scarce information about bioactivity of water extracts of Capsicum spp. (Aliakbarlu et al. 2014). Antioxidant activity of chili pepper varies, depending on the variety, maturity stage, and technique used to measure this capacity (Gahungu et al. 2011; Jang et al. 2008; Aliakbarlu et al. 2014). However, some studies have reported that aqueous extracts of pepper can protect tissues from oxidative stress and from lipid peroxidation from diverse causes (Oboh et al. 2007; Otunola et al. 2010). This protective effect from the


aqueous extracts is attributed to the presence of antioxidants, especially ascorbic acid and polyphenols (Oboh et al. 2007). Moreover, the consumption of C. frustescens may help to modulate oxidative stress caused by hyper-cholesterolemia in rats (Outunola et al. 2014). Volatile compounds in water extracts of some Habanero chili pepper cultivars have been identified and showed that orange and brown varieties have in general higher amounts of esters that enhance their flavorrelevant chemical composition (Pino et al. 2007). In high hot Scotch bonnet chili pepper, at the red stage were identified 70 volatile compounds (Gahungu et al. 2011). However, in green chili pepper, only 12 volatile compounds were found as major aroma compounds (Jang et al. 2008). Barbero et al. 2008 compared different extraction solvents to recover capsaicinoids from hot Cayenne pepper and found that water, which is a very polar solvent, has a poor capacity of extraction. This reduced effectiveness is accentuated in the case of less polar capsaicinoids such as dihydrocapsaicin, homocapsaicin, and homodihydrocapsaicin in comparison with more polar capsaicinoids as nordihydrocapsaicin and capsaicin. On the other hand, Bajer et al. 2015 compared the extraction of capsaicinoids from ten chili samples using PHWE and Soxhlet extraction obtaining better extraction yields in the first case with lower times and no contaminant solvents (Bajer et al. 2015). In addition, in vitro studies about water extracts of macerated Capsicum spp. reported an antimetastasic activity against human breast cancer cells (Kim et al. 2014) as well as antiobesity activity (Back et al. 2013). Moreover, water extracts of bell Pepper showed ACE inhibitory activity (Kwon et al. 2011). Water extract of C. pubescens showed ability to inhibit lipid peroxidation in rat’s brain homogenates probably due to its phenol content and reducing power (Oboh et al. 2007). However, the most frequently use of water extracts from hot chili peppers is as a source of natural pesticides and insecticides for agriculture and even to reduce some human wildlife conflicts (Parker and Osborn 2006). Olive oil aromatized with C. frutescens showed an increase in its content of all the isoforms of vitamin E (from 186.4 in control to 198.6 mg/kg olive oil) increasing also the nutritional value but the phenolic content decreased from 345 in control to 336 mg caffeic acid/kg olive oil in hot chili pepper (Sousa et al. 2015). However, the effect of the addition of hot chili pepper in the antioxidant potential is still unclear. Caporaso et al. (2013) found a significant increase in the infused olive oil. However, other authors observed that the antioxidant potential decreases with the addition of dried chili (Baiano et al. 2009; Sousa et al. 2015). Equally, the content of phenolic compounds has been also reported lower than in unflavored olive oil (Sousa et al. 2015; Baiano et al. 2009). The infusion time and the dried chili pepper concentration are crucial for the production of flavored oils. Hence, the content of capsaicinoids in chili flavored oil is maximum at 7 days, and

69

no significant increase was observed for longer infusion times and antioxidant activity is reduced after the first week of storage (Caporaso et al. 2013). The volatile composition of the olive oil was influenced by the concentration of dried chili pepper added as an increase in hexanal related to oxidation processes. The presence of dried chili pepper in enriched olive oils with antioxidant compounds also modified its volatiles profile. However, capsaicinoids and aroma compounds were rapidly released within the first week of chili infusion (Caporaso et al. 2013). Other study showed that, in long time storage periods, the presence of a hot chili oleoresin improved the oxidative stability of the extra virgin olive oil (Gambacorta et al. 2007). In the case of several cultivars of C. annuum extracted by Soxhlet with different organic solvents (hexane, ethyl acetate, acetone, methanol, and methanol/water), the highest levels of capsaicinoids and carotenoids were found with hexane but the maximum level of flavonoids were found with methanol (Bae et al. 2012b). Moreover, methanol extracts from C. annuum L. seeds showed strong anti-proliferative activity against MCF7, MKn45, and HCT116 tumor cells at a concentration of 500 μg/ mL due to an increase in apoptosis (Jeon et al. 2012). C. chinense (Habanero) ethanol extracts showed high amounts of antioxidant properties since the extract contained compounds such as carotenoids, vitamins, phenolics, and capsaicinoids (Castro-Concha et al. 2014). C. annuum and C. chinense cultivars showed different levels of antioxidant activity and reducing activity based on their content of capsaicinoids, carotenoids, flavonoids, and phenolics. The maximum antioxidant activity was showed using hexane as solvent while the inhibition of deoxyribose degradation was higher in methanol (Bae et al. 2012b). The extraction with acetonitrile of a C. fruscences variety presented more phenolics in comparison when hexane was used as extraction solvent resulting in a higher antioxidant activity (Nascimento et al. 2014). In fact, polar aprotic solvents such as acetonitrile and acetone were more efficient to extract capsaicinoids than non-polar solvents (Amruthraj 2014). Similarly, ethanolic extracts showed high flavonoids and phenol contents (Rahiman et al. 2013), but in some cases, low DPPH activity was found (Rahiman et al. 2013). Ethanolic and butanolic extracts from C. baccatum contained potential antioxidant and anti-inflammatory compounds which were tested against oxidative and inflammation-related pathological processes. The appropriate use of solvents could be potentially useful to measure and to extract the maximum antioxidant and nutritional value of Capsicum (Bae et al. 2012b). C. chacoense Hunz contained similar amounts of capsaicin in comparison with C. baccatum and C. annuum L. Moreover, dichloroethane and ethanol extracts of


C. chacoense and C. baccatum L. elicited inhibition on the araquidonic acid pathway in ear edema and could be used as well in human nutrition as phyto-preventives (López et al. 2014). Seed extracts from C. annuum L. showed relatively low antioxidant activity and polyphenolic content, but exerted high antiproliferative effects on tumor cells, even at low concentrations (Jeon et al. 2012). Finally, Capsicum spp. oleoresins have exhibited superoxide anion radical scavenging activity as well as antiproliferative activity in MCF7, HT-29, and HeLa cell lines (Šaponjac et al. 2014). Antimicrobial Activity The microbial safety of foods is one of the major concerns to consumers, regulatory agencies, and food industries. Many food preservation strategies have been used traditionally for the control of microbial spoilage in foods, but the contamination is still an issue when is not adequately performed. Although many synthetic antimicrobials are approved in most countries, the recent trends are for the promotion and use of natural preservatives, which are safe, effective, and sensory acceptable. Plants contain innumerable constituents and are valuable sources of new and biologically active molecules with antimicrobial properties against a widespread variety of bacteria, yeast, and molds. However, the variations in quality and quantity of their bioactive compounds are the major disadvantage in their use in foods. Further, phytochemical compounds added to foods may be lost by various processing techniques such as high pressures and temperatures (Singh et al. 2014). The antimicrobial activity in Capsicum spp. seems to be strongly related with the presence of natural antioxidants such as carotenoids than with the pungent components of the fruits. For that, some studies as Dorantes et al. (2000) found that sweet red pepper (C. annuum L.) had more antimicrobial activity against common food pathogens than hot peppers such as Jalapeño. Fresh and heated water extracts of different Capsicum spp. have exhibited different degrees of inhibition against Bacillus cereus, Bacillus subtilis, Clostridium sporogenes, Clostridium tetani, and Streptococcus pyogenes (Cichewicz and Thorpe 1996). Moreover, a little activity against B. cereus, Listeria monocytogenes, and Escherichia coli at high doses (150 mg/ ml) has been found in Iranian red chili (C. annuum L.) (Aliakbarlu et al. 2014). The crude juice of C. frutenscens has shown higher antimicrobial activity against E. coli, Salmonella typhi, and B. subtilis than organic solvent extracts as petroleum-ether, chloroform, isopropanol, and ethanol (Abdou Bouba et al. 2012). However, n-hexane and chloroform extracts from C. frutescens L. showed inhibitory activity against Pseudomonas aeroginosa, Klebsilla pneumonia, Staphylococcus aureus, and Candida albicans (Gurnani


et al. 2015). Other research showed that water extracts of cayenne pepper inhibited the presence of Enterobacter aerogenes and L. monocytogenes (Kumral and Sahin 2003). In the case o C. baccatum L. var. pendulum, the ethanol extract did not show any antimicrobial activity and the only antifungal activity was found in immature seeds ethanol extracts (Kappel et al. 2008). The antimicrobial activity of capsaicin microcapsules on common microorganisms for food preservation such as Bacillus cinerea and Aspergillus niger have been also investigated. The factors affecting the antimicrobial effects, including the microcapsule concentrations, pH values, and release behavior have also been examined. The shelf life of low pH foods (acidic) tends to be better than high pH foods (alkaline) where microorganism can better growth. The optimum antimicrobial effect in Capsicum oleoresins was found at pH 5.0 in shortterm storage foods (Xin et al. 2014). Supercritical CO2 and ethanol extracts from C. annuum and C. frutenscens showed antibacterial effect against Streptococcus sobrinus and S. salivarius. Therefore, there are promising materials for new antiseptical agents for oral care products (Pilna et al. 2015).

Conclusions Oleoresins are natural products that consist of complex mixtures mainly of lipophilic molecules. C. oleoresins have been used for several applications in pharmaceutical, cosmetic, agricultural, and food industries mainly for it sensorial attributes (color and pungency). Moreover, Capsicum spp. oleoresins are rich in bioactive compounds with antimicrobial and antioxidant activities such as carotenoids and capsaicinoids that can be used as a natural additive. However, Capsicum spp. oleoresins have been traditionally extracted by organic solvents that potentially risk both for the environment and human health. Research shown here display the increase of green extraction technologies at the laboratory level. Nonetheless, most of these non-conventional extraction technologies require high production costs, making it unfeasible for its development in emergent countries that are the main Capsicum spp. producers. In this regard, non-conventional extraction with vegetable oils becomes a good green and costefficient alternative to extracting Capsicum compounds. Finally, there is a strong relation between the extraction techniques and the compounds extracted in the case of Capsicum spp. oleoresins due to the different polarity of the extraction solvents. Differences in the polarity of the bioactive compounds to be extracted allow the production of Bintelligent^ oleoresins rich in the selected bioactive compound. Further research should be carried out to understand this matter.

Author's personal copy Food Bioprocess Technol (2017) 10:51–76 Acknowledgments This research was partially supported by Consejo Nacional de Ciencia y Tecnología (Conacyt) through a postdoctoral grant with the agreement number 290807-UV.

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