(citrus sinensis) pulp, a by-product of orange juice ...

Journal of Food Quality ISSN 1745-4557

CHEMICAL AND SENSORY CHARACTERIZATION OF ORANGE (CITRUS SINENSIS) PULP, A BY-PRODUCT OF ORANGE JUICE PROCESSING USING GAS-CHROMATOGRAPHYOLFACTOMETRY SOPHIE DETERRE, CLOTILDE LECLAIR, JINHE BAI, ELIZABETH A. BALDWIN, JAN A. NARCISO and ANNE PLOTTO1 U.S. Horticultural Research Laboratory, USDA-ARS, Fort Pierce, FL 34945

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Corresponding author. TEL: 772-462-5844; FAX: 772-462-5986; EMAIL: [email protected] Mention of a trademark or proprietary product is for identification only and does not imply a guarantee or warranty of the product by the U.S. Department of Agriculture. The U.S. Department of Agriculture prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation and marital or family status. Received for Publication September 28, 2015 Accepted for Publication June 2, 2016 10.1111/jfq.12226

ABSTRACT Volatile composition of commercial orange pulp (from Brazil and Florida, U.S.A.) was analyzed by gas chromatography-mass spectrometry (GC-MS) and GCOlfactometry (GC-O). In both samples 72 volatiles were detected, of which 58 were identified. Odor-active compounds with a high frequency of detection (5 out of 9) or intensity characterizing the aroma of sweet orange pulp were monoterpene hydrocarbons (a-pinene, b-pinene, b-myrcene, a-phellandrene, 3carene, a-terpinene and limonene), ketones (1-octen-3-one, carvone, (E)-bdamascenone and b-ionone), esters (ethyl-2-methyl butanoate and ethyl hexanoate), aldehydes (methional and octanal), alcohols (linalool and 1-octanol) and 3 unidentified compounds. A few differences in the odor-active volatiles between orange pulp samples were perceived, which might be due to cultivar, growing and processing conditions, but overall, the chemical composition of the two samples was similar. Sensory data described both sweet orange pulp samples with descriptors for orange odor and flavor including orange peel and fruity-noncitrus flavor, sweet and sour taste.

PRACTICAL APPLICATIONS Orange pulp is used in the beverage industry to add texture and mouthfeel. It is also added to orange juice for consumer appeal to make it more “natural.” This study characterized the flavor of orange pulp. Orange pulp consisted of yellow– orange floating intact cells. Pulp added to a sugar-acid solution (5% pulp, 10.5% sucrose and 0.25% citric acid) imparted an orange, fruity and fresh flavor. Information from this study on sweet orange pulp flavor will be useful for orange juice processors and beverage manufacturers.

INTRODUCTION Orange juice made from sweet oranges (Citrus sinensis [L.] Osbeck) is the most popular juice beverage around the world. Brazil and the U.S.A. (mainly Florida) have long been the two largest producers of orange juice concentrate (658Brix equivalent) with productions of 1.0 6 0.2 and 0.5 6 0.2 million Metric Tons, respectively, since 2011. These two countries represent 55 and 25% of the world production, respectively (USDA/FAS 2015). During commercial

processing, juice is extracted from oranges by squeezing or reaming the fruit by means of mechanical pressure (Ringblom 2004). The resulting pulpy juice (50% of the orange) is then clarified using various types of screens or finishers to obtain a final juice product with the desired consistency. In the early days (in the 1960–1970s), most solids from the orange, including peel, rag (crushed peel), seeds and segment walls, were sent to the feed mill for drying into pellets for animal feed (Ranganna et al. 1983b; Ringblom 2004).

C 2016 This article is a U.S. Government work and is in the public domain in the USA. Journal of Food Quality 00 (2016) 00–00 V

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CHEMICAL AND SENSORY EVALUATION OF ORANGE PULP

More recently, a diversity of juice types are offered to consumers, with juice having various levels of pulp. Pulp as a by-product of orange juice processing may also be added to other types of drinks and food products to provide a desired texture (Bangert 1976; Loader 1983; Dulebohn et al. 2001; De Moraes Crizel et al. 2013). Orange pulp is composed of pieces of membrane materials from the ruptured juice sacs and segment walls, contributing to the texture and mouthfeel of citrus juice. In the orange juice, pulp is characterized as either “sinking” or “floating”: the “sinking” pulp is an integral part of the juice and consists of small particles (50 h) and evaluating citrus products on a weekly basis. An initial session was performed to choose the best way to present samples and to select the most suitable sensory descriptors for these specific samples. An extensive list of descriptors generated from earlier studies, GC-O and the literature were provided (Perez-Cacho et al. 2008; Plotto et al. 2008). Only the most relevant descriptors were considered: the ones used by at least three panelists out of five for at least one sample (Table 1). Samples were evaluated in duplicate sessions at several days interval, with only undiluted pulp or diluted pulp served in one sitting, since the ballots were different between the two preparation types. Samples in plastic

TABLE 1. SELECTION OF SENSORY DESCRIPTORS USED TO EVALUATE UNDILUTED AND DILUTED SWEET ORANGE PULP

Odor Taste/flavor

Appearance

4

Undiluted Pulp

Diluted pulp

Orange, orange peel, pine-like, fresh, overripe/ cooked, oxidized Sweet, sour, orange, orange peel, fruity-noncitrus, pine-like, spicy/woody, fresh, overripe/ cooked Yellow, orange, brown, homogeneous (uniform), fibrous

Orange, orange peel, fruity-non-citrus, fresh Sweet, sour, orange, orange peel, fruity-noncitrus, fresh, floral White, yellow, homogeneous (uniform), fibrous


S. DETERRE ET AL.

souffle cups labeled with three-digit code numbers were served at 25C and were presented in a monadic manner. Panelists evaluated odor, flavor, and taste in isolated booths under red lighting. Appearance was evaluated in a separate room under day-like lighting. Descriptors were rated on a category scale from 0 (none) to 3 (high).

Data Analysis Analyses of variance (ANOVA) were performed on the maximum peak intensity and peak duration of the GC-O data. Significance at P < 0.05 was chosen for separation of means. Statistical analyses were performed with XLSTAT v 2011.1.05 (Addinsoft, Paris, France). Because the samples were rated on a 0-3 scale, sensory descriptive data were transformed into rank and analyzed using the Mann Whitney test, nonparametric equivalent of the t-test (Lawless and Heymann 1998), using XLSTAT. The level of significance was chosen as P < 0.05. Data are presented as average intensities.

RESULTS AND DISCUSSION Identification of Volatile Compounds in Orange Pulp In both orange pulp samples, 72 volatile components were detected and 58 were identified by GC-MS (Table 2). Mono- (73.56 and 69.89% for the Brazil and Florida pulp, respectively) and sesquiterpene (10.90 and 17.17% for Brazil and Florida pulp, respectively) hydrocarbons were the major components of the pulp and among them, limonene was the most abundant (56.75–59.51%). Hydrocarbons are hydrophobic: their octanol-water partition coefficients (such as limonene 4.57, myrcene 4.17 and caryophyllene 6.30) are higher than those of aldehydes (decanal 3.76), esters (ethyl hexanoate 2.83) or alcohols (linalool 2.97) (S.R.C. 2014). They constitute most of the volatiles detected in the pulp, while the hydrophilic compounds remain in the juice during processing (Brat et al. 2003). In these samples, the hydrophilic compounds detected, 5.97% and 4.32% alcohols, 4.24% and 2.93% aldehydes, 1.60% and 1.93% esters, 0.71% and 1.35% ketones and 0.04% and 0.01% furans (2-ethylfuran) in Brazil and Florida pulp, respectively, may come from the 20% fraction of juice (serum) in the pulp. Twenty-three volatiles, representing 2.99 and 2.40% of the detected volatiles (data not shown), remained unidentified in Brazil and Florida pulp, respectively. We found good agreement with previous studies: among the 58 identified components, for example, 28 volatiles were also reported by Brat et al. (2003), 31 by Jordan et al. (2001), and 21 by Radford et al. (1974) (Tables 2 and 3). Differences in volatile profile between the two types of orange pulp in this study were highlighted with the peak


area ratios between the Brazil and Florida pulp samples (Table 2). The following compounds were detected in the Brazil pulp in at least twice the amount detected in the Florida pulp (ratio values 2): monoterpene hydrocarbon, linear retention indices on DB-5 (IT) 5 1270 (ratio value 5 6.11), sesquiterpene hydrocarbon 1431 (4.39), carvyl acetate (3.69), heptanal (3.60), monoterpene hydrocarbon 995 (2.38), 2ethylfuran (3.12), sesquiterpene hydrocarbon 1458 (2.25) and decanal (2.13). On the contrary, terpinen-4-ol (0.37), sesquiterpene hydrocarbon 1497 (0.38), ethyl butanoate (0.43) and ethyl-3-hydroxyhexanoate (0.45), were detected in the Florida pulp in amounts at least twice as much as in the Brazil pulp (ratio values 0.5). A few components were only detected in the Brazil or in the Florida pulp (Table 3). Two identified (2-butanone and geraniol) and three unidentified volatiles were only detected in the pulp from Brazil, representing 0.59% of the volatiles detected. Four identified (methyl butanoate, methyl hexanoate, 1-octanol, (E)-dihydrocarvone) and five unidentified volatiles, representing 0.76% of the volatiles detected, were only present in the Florida pulp. Varietal, harvest maturity, seasonal and climatic factors are likely to explain the aroma differences between samples, as well as processing parameters and storage conditions. Differences, such as the larger amount of ethyl butanoate and (E)-2-hexenal in the Florida pulp and the larger amount of linalool, ethyl furan and decanal in the Brazil pulp, could be an indication of higher processing temperatures for the Brazilian pulp (Nisperos-Carriedo and Shaw 1990). But if this were the case, low molecular weight volatiles such as ethanol, ethyl acetate and hexanal would be lower in the Brazilian than in the Florida pulp (Perez-Cacho and Rouseff 2008). Alpha- and b-terpineol, as well as terpinen-4-ol and geraniol are thermally induced volatiles from limonene or linalool (Perez-Cacho and Rouseff 2008). In our study, terpinen-4-ol was higher in the Florida sample, a- and bterpineol were higher and geraniol was only detected in the Brazil sample, indicating no definite differences in temperature during processing and storage of these samples. Perhaps higher a- and b-terpineol and geraniol in the Brazil sample simply indicate differences in the raw orange fruit material. Overall, the differences in volatiles between the two pulp sources were minimal, as can be seen on a representative chromatogram of each sample (Fig. 2).

Identification of Odor-Active Compounds in Orange Pulp from Brazil and Florida Thirty-three odor-active volatiles were detected and characterized in diluted orange pulp samples by one or several odor descriptors (Table 4). Among these 33 volatiles, eight remain unidentified, IT 5 650, 765, 812, 857, 1068, 1147, 1207 and 1229, and nine were not detected by GC-MS but identified by IT and sniffing of pure standards: ethyl-2-


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TABLE 2. VOLATILE COMPOUNDS (EXPRESSED AS TOTAL ION CURRENT 31023 6 STANDARD DEVIATION) FROM UNDILUTED SWEET ORANGE PULP FROM BRAZIL AND FLORIDA PRESENTED BY CHEMICAL FAMILY (N 5 3) IT

IT

Brazil †

Florida

Family

DB-5 DB-Wax

Compound*

Identification

Alcohols

510 1102 1127 1190 1225 1236 1282

Ethanolc 1-Octanola,b,c Linaloola,b,c b-Terpineol Terpinen-4-ola,b,c a-Terpineola,b,c Geraniolb,c

Standard, Standard, Standard, Standard, Standard, Standard, Standard,

MS, MS, MS, MS, MS, MS, MS,

IT IT IT IT IT IT IT

184,248 nd 613,273 19,165 59,894 110,476 13,433

Hexanala,b,c (E)-2-hexenal Heptanal Benzaldehydeb Octanala,b,c Nonanala,b,c Decanala,b,c Geranialc Perillaldehydec Undecanalc

Standard, Standard, Standard, Standard, Standard, Standard, Standard, Standard, Standard, Standard,

MS, MS, MS, MS, MS, MS, MS, MS, MS, MS,

IT IT IT IT IT IT IT IT IT IT

29,754 8,731 38,768 2,796 223,341 86,775 250,878 10,581 47,626 10,945

Ethyl acetateb,c Methyl butanoatea,c Methyl hexanoate Ethyl butanoatea,b,c Ethyl hexanoatea,b Methyl octanoate ethyl-3-hydroxyhexanoatea,b Ethyl octanoateb n-Octyl acetatec Methyl geraniate (E)-carvyl acetate Neryl acetate Geranyl acetate

Standard, Standard, Standard, Standard, Standard, Standard, Standard, Standard, Standard, MS, IT MS, IT Standard, Standard,

MS, MS, MS, MS, MS, MS, MS, MS, MS,

IT IT IT IT IT IT IT IT IT

4,538 nd nd 24,517 97,781 13,265 28,551 27,732 42,309 5,267 6,801 9,210 7,650

966 1587 1572 1645 1726

Average

% Alcohols Aldehydes

1326 1397 1509 2052

% Aldehydes Esters

871

1050 1252 1712 1460 1476

MS, IT MS, IT

587 932 1240 1284 1778

2-Butanone (E)-dihydrocarvone Carvonec

MS, I Standard, MS, IT Standard, MS, IT

682

2-Ethylfuran

MS, IT

6

34,457 16,601 10,773 1,964 206,981 60,845 117,758 9,763 40,195 5,615

561 1,891 2,888 268 2,871 1,963 2,946 381 323 649 536

4,487 2,112 10,242 57,567 109,600 12,876 62,961 20,908 30,330 2,757 1,845 7,515 8,651

13,642 nd 106,102

6,704

945 959 1033 981 995 1002 1009 1192/1143 (b-myrcene/ b-pinene) 1037 1038 1170 1042 1239

a-Thujene a-Pinenea,b,c Camphene n.i Sabinenea,b,c b-Myrcenea,b,c1 b-pineneb,c n.i a-Phellandrenec d-3-careneb,c

MS, I Standard, MS, IT Standard, MS, IT

4,346 212,997 3,824 11,054 Standard, MS, IT 8,329 Standard, MS, IT 1,098,640

Standard, MS, IT Standard, MS, IT

47,985 49,379 72,147

6 2,137 0.86 6 1,801 0.53 6 1,430 3.60 6 65 1.42 6 11,927 1.08 6 3,600 1.43 6 7,491 2.13 6 512 1.08 6 1,400 1.18 6 484 1.95

2.93 6

6 6 6 6 6 6 6 6 6 6

6 6 6 6 6 6 6 6 6 6 6 6 6

267 237 401 2,687 5,365 714 4,954 1,381 2,290 422 126 492 619

1.01 0.43 0.89 1.03 0.45 1.33 1.39 1.91 3.69 1.23 0.88

6 6

7,103 7,410 0.51

6

257 3.12

1.93

6

1,214 6,704

nd 26,327 206,928

6

409

2,145

6

1.35

0.04 T

6 32,898 1.55 6 1,927 6 14,530 1.93 6 807 1.49 6 5,501 0.37 6 1,885 1.56 -

4.32

0.71

% Furans Monoterpene hydrocarbons

6 1,673 6 269 6 1,228 6 125 6 13,724 6 6,026 6 17,783 6 195 6 2,933 6 654

1.60 T

% Ketones Furans

119,142 61,790 317,277 12,845 161,998 70,767 nd

4.24 599 703 931 789 1013 1146 1155 1216 1229 1338 1352 1367 1384

% Esters Ketones

6 42,046 6 38,293 6 1,409 6 93,092 6 5,094 6 258

5.97 793 856 910 993 1024 1132 1232 1294 1318 1327

Std. dev. Ratio‡

Std. dev. Average

0.01 6 408 3,496 6 14,278 275,416 6 399 4,559 6 789 4,651 6 817 4,743 6 50,486 1,123,193

6 6 6

2,022 1,328 4,503

52,929 39,577 36,646

6 559 1.24 6 26,762 0.77 6 159 0.84 6 82 2.38 6 420 1.76 6 75,568 0.98

6 6 6

1,901 0.91 2,103 1.25 3,229 1.97


S. DETERRE ET AL.


TABLE 2. CONTINUED IT Family

IT

DB-5 DB-Wax 1050 1059 1061 1073 1075 1092 1123 1162 1171 1179 1270 1370

1184

1214 1263 1307

Brazil Compound* b,c

a-Terpinene n.i n.i Limonenea,b,c n.i c-Terpinenea,b,c Terpinoleneb n.i n.i n.i n.i n.i

Identification† Standard, MS, I

Average T

63,105 17,941 39,789 Standard, MS, IT 9,977,904 322,270 Standard, MS, IT 120,291 Standard, MS, IT 166,663 15,372 26,418 8,391 55,137 10,677

% Monoterpenes Sesquiterpene hydrocarbons

Florida Std. dev. Average 6 872 56,233 6 358 24,144 6 8,771 45,895 6 259,009 9,780,283 6 11,501 274,808 6 7,338 91,088 6 6,269 149,893 6 2,221 17,359 6 1,440 31,619 6 420 6,806 6 6,297 9,028 6 581 11,340

73.56 1378 1409 1415 1431 1453 1458 1471 1483 1490 1497 1504 1511 1514 1518 1521 1535

1528 1644 1638

1900 1913 1907

a-Cubebene a-Copaeneb b-Elemenea n.i b-Caryophyllenea,b,c n.i Alloaromadendrene a-Humulenec c-Muurolene n.i n.i Valencenea,b,c a-Selineneb b-Selinene d-Cadinenea (E)-cadina,1,4-diene

T

Standard, MS, I MS, IT MS, IT MS, IT Standard, MS, IT

6,405 25,398 45,279 8,143 31,342 10,326 Standard, MS, IT 31,567 Standard, MS, IT 6,604 MS, IT 22,888 18,672 117,415 Standard, MS, IT 1,176,407 MS, IT 132,527 MS, IT 57,016 MS, IT 35,680 MS, IT 101,782

% Sesquiterpenes

Std. dev. Ratio‡ 6 993 1.12 6 3,782 0.74 6 3,268 0.87 6 345,014 1.02 6 25,573 1.17 6 4,921 1.32 6 3,257 1.11 6 1,559 0.89 6 879 0.84 6 539 1.23 6 873 6.11 6 724 0.94

69.89 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6

323 6,575 1,399 17,947 2,271 37,572 410 1,856 1,670 42,964 669 4,596 1,768 61,638 414 11,918 1,184 37,090 11,925 49,160 6,200 200,834 40,423 1,908,924 5,915 225,222 3,238 112,414 2,728 45,089 6,151 195,154

10.90

6 573 0.97 6 2,025 1.42 6 4,388 1.21 6 158 4.39 6 4,772 0.73 6 527 2.25 6 7,042 0.51 6 1,091 0.55 6 3,188 0.62 6 5,465 0.38 6 21,699 0.58 6 136,812 0.62 6 22,908 0.59 6 11,704 0.51 6 4,375 0.79 6 21,206 0.52

17.17

Ratio of Brazil/Florida (bold italics) showed when compounds were detected twice as much in Brazil than in Florida samples (2), and twice as much in Florida than in Brazil samples (0.5). *Reported in: aRadford et al. (1974), bBrat et al. (2003) and cJordan et al. (2001). † Identification by: Standard: Identification based on co-injection with authentic standards by GC-MS. IT, Identification based on IT matching with DB-5 and DBWax columns; and MS, Identification based on mass spectra matching. ‡ Ratio of the averages of peak areas Brazil:Florida. n.i., Non-identified monoterpene or sesquiterpene hydrocarbons (MW 5 136 or 204, respectively). nd, Not detected.

methyl butanoate, methional, 1-octen-3-one, guaiacol, (E)p-2,8-menthadien-1-ol, (E)-2-nonenal, carvone, (E)-bdamascenone and b-ionone. We can hypothesize that these latter components were not detected by GC-MS (in which undiluted samples were run) but only by smell due to their very low odor thresholds in air: recognition at 6.0.102521.2.1024 mg/m3 for ethyl-2-methyl butanoate (Guth and Grosh 1991), detection and recognition at 6.3.1025 mg/m3 for methional (Von Ranson and Belitz 1992), 3.0.102521.2.1024 mg/m3 for 1-octen-3-one (Guth and Grosh 1990), 4.0.1024 mg/m3 for guaiacol (Ferreira

et al. 1998), detection at 2.2.1025 mg/m3 and recognition at 3.9.1025 mg/m3 for (E)-2-nonenal (Von Ranson and Belitz 1992), 16.6.1023 mg/m3 for carvone (Schieberle and Grosch 1989), 2.0.102624.0.1025 mg/m3 for (E)-b-damascenone (Blank et al. 1989, 1992) and 1.2.1024 mg/m3 for b-ionone (Brenna et al. 2002). There are no data reported in the literature for (E)-p-2,8-menthadien-1-ol, and therefore, this compound is only tentatively identified. Guaiacol was reported to be glycosidically bound volatiles in orange pulp (Ren et al. 2015), and 1-octanol and b-damascenone in kiwifruit (Garcia et al. 2013); further, b-damascenone and b-


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S. DETERRE ET AL.

TABLE 3. VOLATILE COMPOUNDS UNIQUE TO EITHER BRAZIL OR FLORIDA SWEET ORANGE PULP Family Ketones Alcohols Unknown compounds

IT

IT

DB-5 587 1282 651 1242 1301

DB-Wax 932

Compound 2-Butanone Geraniol Unknown 651 Unknown 1242 Unknown 1301

Identification*

Brazil

MS, IT Standard, MS, IT

% Total Esters Alcohols Ketones Unknown compounds

Florida

Total ion current 3 106 14 13 4 37 30 0.59

703 931 1102 1240 680 765 927 1126 1390

1587

Methyl butanoate Methyl hexanoate 1-Octanol (E)-dihydrocarvone Unknown 680 Unknown 765 Unknown 927 Unknown 1126 Unknown 1390

Standard, Standard, Standard, Standard,

MS, MS, MS, MS,

% Total

T

I IT IT IT

2 10 62 26 3 2 10 10 5 0.76

*Identification by: Standard: Identification based on co-injection with authentic standards by GC-MS. MS, Identification based on mass spectra matching. IT, Identification based on IT matching with DB-5 and DBWax columns.

FIG. 2. SIDE-BY-SIDE CHROMATOGRAMS OF HEADSPACE VOLATILES OF BRAZIL (TOP) AND FLORIDA (BOTTOM) PULP SAMPLES. IDENTIFIED PEAKS ARE ODOR-ACTIVE BY GC-O (TABLE 4) AND DETECTED BY GC-MS, EXCEPT ETHANOL AND VALENCENE THAT ARE INDICATED AS REFERENCE PEAKS

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TABLE 4. ODOR-ACTIVE COMPOUNDS IDENTIFIED BY GC-O IN DILUTED SWEET ORANGE PULP AND CONFIRMED WITH LITERATURE AND INJECTION OF PURE CHEMICALS Occurrence (Out of 9 repetitions)*

Maximum intensity (From 0 to 10)†

Duration (s)†

IT DB-5

Compounds

Odors descriptors

Florida

Brazil

Florida

Brazil

Florida

Brazil

650 765 785 812 835 857 890 898 927 976 981 992 1000 1006 1033

Unknown 650 Unknown 765 Ethyl butanoate1hexanal Unknown 812 Ethyl-2-methyl butanoate Unknown 857 Heptanal Methional a-Pinene 1-Octen-3-one b-Pinene 1 b-myrcene Ethyl hexanoate Octanal a-Phellandrene d-3-carene a-Terpinene Limonene Unknown 1068 1-Octanol‡ Guaiacol Linalool Unknown 1147 (E)-p-2,8-menthadien-1-ol‡ (E)-2-nonenal b-Terpineol‡ Unknown 1207 Decanal Unknown 1229 Carvone (E)-b-damascenone b-Ionone

Cheese Plastic, green Fruity, candy, green, cooked Waxy, solventy, terpeney Fruity, chemical Fatty, rubber, cooked Plastic, green, fatty Mashed potatoes, green, fatty Citrus, mint, terpene Floral, green, mushroom Candy, floral, green Fruity, candy, citrus, green Citrus, lemon, mint Citrus, lemon, mint Mint, fresh, floral

3 2 9 0 7 9 6 9 9 9 9 3 9 9 8

1 9 2 3 7 7 3 9 8 9 9 3 9 9 8

0.5 0.3 6.2 0.0a 1.8 6.0b 2.8b 6.2 3.2 5.9 9.1 2.1 5.1a 8.8 4.8

0.1 0.3 4.9 0.7b 2.1 4.5a 0.7a 7.4 3.8 7.1 8.7 2.3 7.4b 8.8 5.5

1.2 0.2 10.3 0.0a 3.6 9.9b 3.7b 9.6a 4.5 7.2 13.4 2.2 5.7 13.3 17.1

0.3 1.0 9.8 0.9b 3.3 5.2a 1.2a 14.1b 4.5 7.5 13.2 2.8 6.3 14.2 18.4

Skunk, fatty Mushroom, metallic, green, fatty Smoke, burnt, vanilla Floral, cowslip, plant Floral, candy, unpleasant Green, fresh, floral Cucumber, green, fatty Green, garbage, plastic Green, floral, mint, plastic Citrus, plastic, butter Fatty, skunk Mint Cooked apple Violet

3 6 3 7 4 5 3 6 7 2 9 6 8 5

4 5 3 7 4 4 8 4 6 8 9 5 8 5

2.6 4.0 1.0 5.9 2.4 3.4 0.7a 4.1 2.6 2.3a 5.7 3.8 4.4 3.1

2.3 3.0 1.8 6.5 2.1 2.2 3.8b 3.4 3.1 6.3b 6.4 3.4 3.9 2.2

2.2 6.7 2.2 9.9 3.6 5.5 1.3a 6.7 3.3 2.4a 12.7 12.2 24.6 12.7

2 7.1 2.2 14.4 3.1 3 5.8b 4.9 5.3 8.1b 17.6 7.9 16.2 14.8

1068 1082 1105 1105 1147 1161 1168 1174 1207 1219 1229 1257 1393 1495

*Occurrence greater than 5 is indicated in bold numbers. Means followed by letter a or b are significantly different from each other for either intensity or duration. Significance indicated in bold highlights. ‡ Tentative identification. All other compounds identification was confirmed by sniffing pure standards. †

ionone are volatiles derived from carotenoid degradation (Perez-Cacho and Rouseff 2008). These volatiles with very low odor threshold and bound to the pulp would contribute to flavor in juice with pulp as they tend to be retained by the nonsoluble fraction of the pulp. Among the odor-active compounds, 20 were detected with an occurrence 5 out of 9 GC-O sessions (Table 4) in both pulp samples, and so can be considered as characteristic of the sweet orange pulp: seven monoterpene hydrocarbons: a-pinene, b-pinene 1 b-myrcene (co-eluting compounds), a-phellandrene, 3-carene, a-terpinene, and limonene, all coeluting compounds by GC-O; four ketones: 1-octen-3-one,

carvone, (E)-b-damascenone and b-ionone, two esters: ethyl-2-methyl butanoate and ethyl hexanoate; two aldehydes: methional and octanal, two alcohols: linalool and 1octanol and three unknown components: at IT 5 857 with fatty, rubber and cooked odors; at IT 5 1207 with green, floral, mint and plastic odors; and at IT 5 1229 with fatty and skunk odors. As we could not find any published report about orange pulp odor components, we compared our findings to orange juice odor volatiles. Some volatiles found in this study were also reported in orange juice with similar odor descriptors such as ethyl butanoate, hexanal, a-pinene, b-pinene, b-myrcene, ethyl hexanoate, octanal, limonene,


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1-octanol, linalool, decanal and b-ionone (Rega et al. 2003, 2004; Perez-Cacho and Rouseff 2008). Regarding the odor differences between the two samples, compounds perceived more frequently in the Brazil pulp than in the Florida pulp were unknown 765 (plastic, green), (E)-2-nonenal (cucumber, green, fatty) and decanal (plastic, butter, citrus). Moreover, unknown 812 (waxy, solventy, terpeney), (E)-2-nonenal and decanal were perceived more intensely and for a longer duration of time in Brazil pulp compared to Florida pulp. In the same way, methional (mashed potato, green, fatty) was perceived for a longer duration time and ethyl hexanoate (citrus, lemon, mint) odor was detected more intensely in the Brazil than in the Florida pulp. On the other hand, co-eluting ethyl butanoate and hexanal (one peak with fruity/candy and green odors), heptanal (plastic, green, fatty), (E)-p22,8-menthadien-1-ol (green, fresh, floral) and b-terpineol (green, garbage, plastic) were perceived with greater frequency in the Florida than Brazil pulp. In the former sample, heptanal and unknown 857 odors were significantly more intense and perceived for a longer duration than in the Brazil pulp. Among all 33 odors compounds, there were also three unknown compounds (at IT5 650, 1068 and 1147) with unpleasant odors, such as cheese, skunk and fatty, but there were no differences between the two samples for occurrences, intensities and durations.

Sensory Attributes of the Orange Pulp Straight undiluted pulp was characterized by orange and overripe/cooked odor, orange, orange peel and fruitynon-citrus flavor, sweet and sour taste as well as a yellow/ orange and homogeneous appearance (rating 1) (Fig. 3). Florida pulp had significantly greater ratings for fresh flavor in comparison with the Brazil pulp, and was more yellow in appearance. The Brazil undiluted pulp had more intense pine-like odor and flavor, and orange and brown appearance in comparison with the Florida pulp. The more intense pine-like odor and flavor intensities in the Brazilian undiluted pulp might be due to the sum of monoterpene hydrocarbons that tended to be either higher or at about the same level in the Brazilian compared to the Florida pulp (Table 2). Differences in appearance and flavor between the two pulp samples might be an indication of more peel components in the pulp from Brazil than in the pulp from Florida, with more carotenoids imparting orange-brown appearance and terpenoids imparting pine-like flavor, or it could be due to varietal differences, processing and/or storage conditions. Slightly higher processing or pasteurization temperatures could induce oxidation and browning, explaining the color and odor differences in the Brazilian pulp (Moshonas and Shaw 1997; Perez-Cacho and Rouseff 2008). But since the 10

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FIG. 3. DISTRIBUTION OF THE SENSORY DESCRIPTORS ACCORDING TO THE MEAN OF THE INTENSITIES (FROM 0 TO 3) RATED FOR THE BRAZIL (- - -) AND FLORIDA (____) UNDILUTED ORANGE PULP Descriptors preceded with the capital letters “O,” “F,” “T” and “A” refer to “ODOR,” “FLAVOR,” “TASTE” and “APPEARANCE,” respectively. *Significant difference between the two types of pulp by the Mann Whitney test (P 0.05).

raw material and processing conditions were unknown, these explanations remain in the realm of speculations. Sensory tests were also performed after diluting pulp by 5% in a sucrose/citric acid solution, to simulate orange drinks that incorporate this type of pulp by-product. Regardless of the sample batch, diluted pulp was characterized by an orange odor, and orange and fruity-non-citrus flavor, sweet and sour taste, as well as by a yellow and fibrous appearance (rating 1) (Fig. 4). The fibrous appearance was due to the pulp cells floating on the surface of the solution (Fig. 1A). The diluted pulp from Brazil had more intense orange peel odor and flavor than the one from Florida. Pine-like odor and flavor were not included in the ballot describing diluted pulp, but these descriptors were rated higher in the Brazil pure pulp in comparison with the Florida pure pulp, which could explain the contribution to a greater orange peel odor and flavor once diluted. The color differences between the two batches of straight pulp, orange/ brown for Brazil and yellow for Florida (Fig. 3) became yellow and white for the diluted pulp from Brazil and Florida, respectively (Fig. 4). By comparing the two types of pulp preparations (undiluted and diluted), undiluted pulp had more intense orange peel and fruity-non-citrus flavor than the diluted pulp. More descriptors were also chosen for the undiluted pulp, such as pine-like, spicy/woody, overripe/cooked and oxidized, meanwhile floral was only used to describe


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FIG. 4. DISTRIBUTION OF THE SENSORY DESCRIPTORS ACCORDING TO THE MEAN OF THE INTENSITIES (FROM 0 TO 3) RATED FOR THE BRAZIL (- - -) AND FLORIDA (____) DILUTED ORANGE PULP Descriptors preceded with the capital letters “O,” “F,” “T” and “A” refer to “ODOR,” “FLAVOR,” “TASTE” and “APPEARANCE,” respectively. *Significant difference between the two types of pulp by the Mann Whitney test (P 0.05).

diluted pulp. The sweet and sour taste perceived in the straight pulp samples was due to soluble compounds in the 20% juice constituting the pulp sample. Interestingly, bitterness was not perceived in these samples, indicating little to no presence of peel components. Regarding the two geographical origins, it is not clear whether the odoractive compounds that were detected by GC-O with greater frequency in the Florida than in the Brazil pulp including fruity, candy, green, cooked, plastic, fatty and floral odors, are responsible for the fresh flavor perceived more intensely in the Florida than in the Brazil undiluted pulp. In the same way, the odor-active compounds detected by GC-O with greater frequency and/or intensity in the Brazil compared to the Florida pulp including plastic, green, cucumber, fatty, butter and citrus odors, may be responsible for the oxidized and pine-like odors perceived more intensely in Brazil than Florida undiluted pulp.

CONCLUSIONS Sweet orange pulp is used by the beverage industry to add to juice or drink products for flavor, texture and to add a fresh juice-like quality. To our knowledge, this is the first report on the odor activity of a commercially derived pulp by-product that would be imparted to juice or juice drinks. Odor-active components of two different batches of sweet orange pulp were analyzed by GC-MS, GC-O and a sensory panel. Chemical compositions were similar;


however differences in peak area were detected by GC-MS. Among the 33 odor-active volatiles detected, 20 characterized the orange pulp aroma. A few significant odor differences could be highlighted between the two types of pulp by named geographical origin. For example, more intense cucumber, green and fatty notes from (E)-2-nonenal were detected in the Brazil pulp, and more intense plastic, green and fatty notes from heptanal were detected in the Florida pulp. Regardless of the origin, results from sensory analysis made it possible to characterize orange pulp cells as having an orange odor and orange, orange peel and fruity-non-citrus flavor, sweet and sour taste, with yellow to brown homogeneous appearance. Pulp diluted in a drink would contribute to orange odor and flavor, adding pleasant, sweet and sour tastes, with fibrous appearance from the pulp cells. From this study, beverage processors may better target which odor, flavor and color might best complement a particular commercial orange juice or juice drink product by the addition of sweet orange pulp.

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