Trends in Food Science & Technology 69 (2017) 1e12
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Review
Innovative technologies for encapsulation of Mediterranean plants extracts Marko Vincekovi c a, Marko Viski c a, Slaven Juri c a, Jasminka Giacometti b, Danijela Bursa c Kova cevi c c, **, Predrag Putnik c, *, Francesco Donsì d, e, Francisco J. Barba f, c Anet Re zek Jambrak University of Zagreb, Faculty of Agriculture, Department of Chemistry, Hall 3, 2. Floor, Svetosimunska cesta 25, 10000 Zagreb, Croatia Department of Biotechnology, University of Rijeka, Radmile Matejcic 2, HR 51000 Rijeka, Croatia Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia d Department of Industrial Engineering, University of Salerno, via Giovanni Paolo II 132, 84084 Fisciano, Italy e ProdAl Scarl, via Ponte don Melillo, 84084 Fisciano, SA, Italy f Nutrition and Food Science Area, Preventive Medicine and Public Health, Food Science, Toxicology and Forensic Medicine Department, Faculty of Pharmacy, Universitat de Val encia, Avda. Vicent Andr es Estell es, s/n, Burjassot, 46100, Val encia, Spain a
b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 13 July 2017 Received in revised form 5 August 2017 Accepted 6 August 2017 Available online 18 August 2017
Background: High-added value biological compounds (BACs) from herbal and plant sources, such as essential oils (EO), antioxidants and volatile compounds, often exhibit remarkable features, ranging from nutritive and medicinal properties, as well as antimicrobial and antioxidant activities, which can be exploited in the production of functional foods. However, most BACs exhibit low water solubility, strong off-flavors/odors, and are generally unstable and easily degraded under common processing and storage conditions. Encapsulation is a technology that enables the delivery in food systems, the protection, as well as the controlled and targeted release of BACs. Scope and approach: The aim of this review is to summarize the most important information for encapsulation of natural extracts using unconventional technologies. Key findings and conclusions: Encapsulation is an excellent choice to stabilize BACs, and in particular EOs, and mask their strong flavors and odors. In particular, spray drying is one of the most economic and common encapsulation technologies. However, the challenges of reducing the operating costs, of developing high-throughput processes, of minimizing the use of organic solvents, and of increasing the level of functionality of the encapsulation systems are driving the research towards the implementation of innovative strategies and non-conventional methods, which incorporate the concepts of Green Food Processing. © 2017 Elsevier Ltd. All rights reserved.
Keywords: Encapsulation Plant extract Bioactive compounds Essential oils Volatile compounds Mediterranean herbs
1. Introduction Encapsulation is a technology, which is specifically suitable to deliver high-added value compounds, able to stabilize and control the release, of high-added value compounds extracted from fruits, vegetables or waste materials (i.e. antioxidant bioactive compounds, vitamins, acidulants, flavors, aromas, enzymes, microbial cells and others) into products. It is a common practice in the
* Corresponding author. ** Corresponding author. E-mail addresses:
[email protected] (D. Bursa c Kova cevi c), pputnik@alumni. uconn.edu (P. Putnik). http://dx.doi.org/10.1016/j.tifs.2017.08.001 0924-2244/© 2017 Elsevier Ltd. All rights reserved.
preservation or improvement of bioactivity of natural extracts (Nikmaram et al., 2017). Over the last years, encapsulation has attracted a significant interest from food, pharmaceutical, nutraceutical, and cosmetic industries, due to its wide application in the design of functional products such as foods and/or food ingredients. The different encapsulation processes can be classified as mechanical, physical and chemical (Gouin, 2004). From ancient times, herbs were used as foods, medicine, and for cosmetic purposes. Their rich aromas made them suitable for poultices and imbibed infusions for various medicinal purposes. Such medicinal properties include anti-allergic, antioxidant, antibacterial, anti-inflammatory, and antiviral. Most of these properties can be attributed to its high BAC content (e.g. polyphenols,
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isothiocyanates, etc.). Nutrients found in herbs include vitamins, proteins, minerals, and antioxidants. Various sources report a great number of potentially beneficial herbal compounds and their multifunctional properties for the production of health-promoting nutraceuticals, food additives/supplements, etc. (Barba, Esteve, & Frígola, 2014; Granato, Nunes, & Barba, 2017; Hashemi et al., 2017). 2. Mediterranean herbs Medicinal and aromatic Mediterranean herbs were used since antiquity for healing (Kumar, Kumar, & Khan, 2011) and for flavoring (Petrovska, 2012). More than 30% of the entire plant species are utilized for medicinal purposes with approximately about 21,000 plant taxa (Groombridge, 1992). Twenty-five percent of worldwide prescribed drugs originated from plants (Sahoo, Manchikanti, & Dey, 2010). Thus, the importance of medicinal plants for the economy is constantly growing. Among the Mediterranean herbs, oregano, basil, rosemary, sage and thyme are regularly used and consumed as fresh or dried. In addition, these herbs are the essential components of Greek, Middle-eastern, Northern African, and Italian cuisine (Barba et al., 2014). Aside as folk medicine, they were used for other purposes, including food preservation that gradually spread around the world (Putnik, Bursa c Kova cevi c, Penic, & Dragovic-Uzelac, 2015; Putnik, Bursa c Kova cevi c, Peni c, Feges, & Dragovic-Uzelac, 2016). Some of the main medicinal benefits are derived from the high content of micronutrients and BACs (e.g. polyphenols), many of which possess powerful antioxidant activity with ability to act as antimicrobials and/or to prevent onset of chronic and degenerative diseases (Barba et al., 2014; Krishnan, Kshirsagar, & Singhal, 2005). Recently, it was clinically verified that the plant extracts that contain BACs may be beneficial in treatment of chronic conditions such as: cardiovascular disease, diabetes, obesity, hypertension, and stimulation of immune response (Deshpande, Neelakanta, & Hegde, 2006; Masella et al., 2004; Noratto, Porter, Byrne, & Cisneros-Zevallos, 2009; Rosenblat & Aviram, 2009; Spencer, Rice-Evans, & Williams, 2003). Additionally, various studies confirmed that different BACs were associated with anti-microbial, antioxidant, anti-mutagenic, anti-chemotactic, anti-cancer, antiinflammatory, anti-genotoxic, hypocholesterolemic functions, and that are beneficial for treatment of gastrointestinal conditions € r S¸at, Beydemir, Elmastas¸, & (Durling et al., 2007; Gülçin, Güngo _ Irfan Küfrevioǧlu, 2004; Harbourne, Jacquier, & O'Riordan, 2009; Lv et al., 2012; Petronilho, Maraschin, Coimbra, & Rocha, 2012; Roby, Sarhan, Selim, & Khalel, 2013; Singh, Shushni, & Belkheir, ). For instance, Yoo, Lee, Lee, Moon, and Lee (2008) investigated relative antioxidant and cytoprotective activities of 17 selected herbs. Their results confirmed the higher protective effect on gapejunction intercellular communication (GJIC) as compared to gallic acid and catechin. Enhanced activity of the antioxidative enzymes (superoxide dismutase and catalase) was evident in a dose-dependent manner (Yoo et al., 2008). However, there is a lack of clear understanding of undergoing physiological pathways in humans (Petronilho et al., 2012). Nevertheless, antioxidants from natural sources are more readily acceptable than synthetic ones, therefore much focus has been given to identifying the active compounds in plants with respect to research-based evidence of its biological effects (Pokorný, 2007). There is scarce literature on the health effects of whole herbs or extracts of entire herbs (Paur, Carlsen, Halvorsen, & R., 2011). 3. Extraction techniques prior encapsulation Each particular family, genera and species of the Mediterranean herbs is characterized by a peculiar content of BACs. With regards to
the chemical structure, BACs can be classified into several categories (e.g. polyphenols, alkaloids, terpenoids, organosulfur compounds, etc.) (Tiwari, Brunton, & Brennan, 2013), with great structural diversity and different physical/chemical properties (e.g. many are thermally unstable). Accordingly, extraction of BACs from Mediterranean herbs can be a daunting and challenging task. Many recent studies focused on finding the most appropriate approach to obtain high-quality BAC in the extraction of various plant materials (Barba, Zhu, Koubaa, de Souza Sant'Ana, & Orlien, 2016; Lovri c, Putnik, Bursa c Kova cevi c, Juki c, & Dragovi c-Uzelac, 2017; Poojary et al., 2017; Putnik, Bursac Kovacevc et al., 2017; Putnik et al., 2016; Putnik, Bursa c Kovacevic, Radojcin, & Dragovi c-Uzelac, 2017; Putnik, Bursa c Kova cevi c, Re zek Jambrak et al., 2017). The most frequently used techniques includes heated conventional extractions (CE) with solvents and agitation, mainly because of their simplicity, low cost, and versatility. Selection of the most appropriate technique relies on the selection of the right solvent for the particular plant, as one of the most important factors that defines the extraction efficiency (Gupta, 2012). On one side, the CE is indeed a relatively simple method, but on the other it can be rather slow with poor extraction efficiency, consume large quantities of organic solvents, and cause thermal degradation of target compounds (Wang & Weller, 2006). Therefore, the application of advanced methods is suggested to decrease the length of the extractions (Dragovi c-Uzelac et al., 2015), the solvents consumption, as well as the increase of yield and quality of the extracts. For instance, extractions with the assistance of microwaves (MAE), ultrasound (UAE), and high-pressure (HPAE) in comparison to the CE offer highly selective and efficient recovery of the high-quality BAC extracts from different plants (Bursac Kova cevi c et al., 2015; Zhang et al., 2011). Moreover, extractions with ultra-high pressure (UPE) (Xi, 2015), negative pressure cavitation (NPC) (Roohinejad et al., 2016), high voltage electrical discharges (HVED), pulsed electric fields (PEF) (Barba, Galanakis, Esteve, Frigola, & Vorobiev, 2015), and mechano-chemical methods (Wu, Ju, Deng, & Xi, 2017), resulted to be very efficient in recovering BACs from plants. These techniques are able to provide valuable plant extracts in an environmentally friendly way, that is well aligned with the nowadays preferred “green concepts” (Herrero, Plaza, Cifuentes, & n ~ ez, 2010). These procedures are rapid, convenient, economical, Iba sustainable, and efficient, and with great potential for industrial upscaling (Chemat et al., 2017). 4. Encapsulation of bioactive compounds Encapsulation is one of the most intriguing fields in the area of active agents' delivery systems. This interdisciplinary technology requires fundamental competences on colloid and interface chemistry, material science, and in-depth understanding of active agents’ stabilization (Rodham, 2000; Thies, 2006). Encapsulation can be described as a method of entrapment of a core material (i.e. active ingredient, fill, internal phase, or payload phase) within another solid or liquid immiscible substance, thereby producing capsules with diameters ranging approximately from 10 nm to 10 mm (Donsì, Sessa, & Ferrari, 2016). Core materials include solid particles, liquid droplets, or gas bubbles. The immiscible substance is also known as the carrier(s) or wall material, shell, coating, membrane, external phase, or matrix. Generally, one can differentiate between two main forms and structures (morphology) of encapsulated systems, namely core-shell type (capsules) and matrix (spheres) type, which are schematically shown in Fig. 1. In the core-shell type, the core material forms a continuous phase enclosed in a shell, while the matrix type has core material uniformly distributed inside a homogeneous solidphase matrix. In addition to these basic morphologies, capsules
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Fig. 1. a) Capsule (core-shell) and b) sphere (matrix type) encapsulation system; the active component is indicated in black and the carrier material in grey. Adapted with permission from “Electrodynamic microencapsulation technology” by (Jaworek, 2006).
can also be polynuclear (many cores enclosed within the shell, where they may form clusters of capsules or other structures). Nanometric-size encapsulation systems are generally of matrix type (nanoemulsions, micelles, microemulsions, and molecular complexes), because of the current limitations in the capability of structure manipulation at the nanoscale, whereas micro and macrometric size systems are more suitable for core/shell or even more complex structures (i.e. combination of a microsphere and microcapsule) and usually are made from biopolymeric material. Morphology has an important influence on the loading capacity, as generally, the increase in system complexity leads to a decrease in the loading capacity. With the proper selection of the main constituents (core and carrier), capsules or spheres can be tailored for numerous industrial applications in the pharmaceutical, chemical, medical, agricultural, and food fields. Lately, encapsulation has received a significant scientific and industrial interest in the preparation of functional foods for the delivery of phytochemicals, micronutrients, dietary fibers, prebiotics, probiotics, etc. (Donsì et al., 2016). The interest towards this technique has been further reinforced by the increasing consumers' and manufacturers’ requests for food products with health-beneficial and disease-prevention functionality, with particular reference to weight control, prevention of diabetes and cardiovascular diseases, digestive health, immune function, anti-ageing, and health protection. The BACs are extremely sensitive compounds, which are often degraded or deactivated during formulation, processing, and storage. Encapsulation enables protection of BACs from the environmental stresses such as exposure to oxygen, water, and light during processing, storage, and transport. This will assure the preservation of nutritional value, bioavailability, solubility, and functionality. In addition, encapsulation might also contribute to mask off-flavors and odors, deconcentrate, control the release, and stimulate handling core material (Fang & Bhandari, 2010). Therefore, the carrier materials are a determining factor in the delivery of the payload material. The selection of the most suitable carrier depends on several factors including: (i) the process of encapsulation; (ii) the desired functionality for the capsule/sphere; (iii) the ability to meet specified or desired core release rate; (iv) the limited chemical reactivity with the core and food component, during processing and extended storage, respectively; and (v) the cost of the carrier material (Shahidi & Han, 1993; Wandrey, Bartkowiak, & Harding, 2010). The carrier materials for food BACs are general biomaterials approved for food uses and “generally recognized as safe” (GRAS). The wide variety of available biomaterials and the lack of a systematic categorization in the material database(s) complicates the
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selection of the most appropriate carrier material, often leaving the choices to a trial-and-error empirical practice. The most desired properties of the material include the inertness towards the BACs and film-forming properties. Furthermore, the carrier should exhibit at least one of the following properties: flexibility, brittleness, hardness, and thinness. It has to be tractable, tasteless, stable and non-hygroscopic, moderately viscous, meltable, soluble in aqueous media or in food-compatible solvents, and economic. The most commonly applied food grade materials are carbohydrate polymers, proteins, and lipids. Fig. 2 provides a graphic list of biomaterials, which are suitable to be used as carriers in the encapsulation for the food manufacturing (Wandrey et al., 2010). The controlled and selective release of encapsulated BACs at the appropriate time and place is one of the essential properties (Desai & Jin Park, 2005). In accord with the European Directive definition (3AQ19a) the controlled release is a “modification of the rate or place at which an active substance is released”. It is possible to differentiate between delayed release (active substance has postponed discharge from a predetermined “lag time” until release is executed without interruption), and continued release (active substance has continued discharge and with constant concertation). Various mechanisms such as surface wetting, penetration of water into the capsule/sphere, swelling, diffusion of the loaded bioactive agents through the capsule/sphere and surface layer, desorption from the surface, disintegration, dissolution or erosion of the capsule/sphere structure, or their combination, may be included in the discharging the active substance. The mechanism controlling the active agent release primarily is influenced by the characteristics of capsule/ sphere material and the type of active agents. Possible mechanisms involved in the core release are diffusion, dissolution, erosion, digestion, mechanical disruption, and triggered release with a change of temperature, pH, pressure, and ionic force. A combination of more than one mechanism often occurs. The engineering of the capsules/spheres can be classified to: (i) physicochemical processes (simple or complex coacervation, ionic gelation, emulsification, liposome encapsulation, solvent evaporation/extraction); (ii) mechanical methods (spray -drying, -cooling, -chilling; fluid bed coating, extrusion-spheronization, centrifugal extrusion, supercritical fluids procedures); and (iii) chemical processes (interfacial polycondensation, polymerization and crosslinking; and in situ polymerization). With regards to the industrial equipment, the fabrication of capsules/spheres can be classified to: (i) dripping methods (extruding droplets from a nozzle in gentle conditions); (ii) spraying (small droplets are either dried or cooled down); (iii) emulsification (dispersed emulsion droplets may be turned into capsules/spheres by different processes); (iv) spray coating (fluidizing a powder and spraying a coating solution on the fluidized particles); and (v) suspension coating (suspension of particles in solution and formation of a coating layer around the particles). Poncelet identified three fundamental steps for the most of these technologies, which are schematically shown in Fig. 3 (Poncelet, 2006). The first step involves the incorporation of the matrix active ingredients or capsule core by mixing, drying, grinding, dispersing and/or sieving. The second step involves the mechanical processing to produce a dispersion (emulsification, or spraying associated to coating or agglomeration). The third step serves the stabilization of the particles/droplets and the deposition of a coating layer by chemical (polymerization), physicochemical (gelation, coacervation) or physical processes (drying, solidification). Several reviews have been recently focused on the methods for BACs encapsulation (Alvim, Prata, & Grosso, 2017; Chranioti & Tzia, 2014; de Vos, Faas, Spasojevic, & Sikkema, 2010; Donsì et al., 2016; Ezhilarasi, Karthik, Chhanwal, & Anandharamakrishnan, 2013;
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Fig. 2. Food grade materials suitable for encapsulation of bioactive compounds. Adapted with permission from “Materials for Encapsulation” by Wandrey, Bartkowiak, and Harding (2006), pp 31e100, in “Encapsulation Technologies for Active Food Ingredients and Food Processing” Springer (Wandrey et al., 2006).
Fig. 3. Technologies of encapsulation. Adapted with permission from “Microencapsulation: fundamentals, methods and applications” by Poncelet (2006), pp 23e34, in “Surface Chemistry in Biomedical and Environmental Science” Springer (Poncelet, 2006).
Quiros-Sauceda, Ayala-Zavala, Olivas, & Gonzalez-Aguilar, 2014; Zuidam & Shimoni, 2010), showing that, despite the large variety of available encapsulation processes, none of them can be indiscriminately applicable to all the BACs (de Vos et al., 2010). The encapsulation of polyphenolic antioxidants in microbeads was reported from medicinal plant extracts (e.g. raspberry leaf, hawthorn, ground ivy, yarrow, nettle and olive leaf) using an alginateechitosan system, where the solubilization of chitosan was improved by ascorbic acid (Bels cak-Cvitanovi c et al., 2011). Herbal extracts were prepared by stirring the plant material in distilled boiling water for 30 min. The microbeads, obtained by electrostatic extrusion, exhibited a significant polyphenol content and high antioxidant activity. Among the six examined plants, nettle showed the poorest encapsulation potential, due to a high content of two valent cations,
which affected the gelation of alginate, thus limiting the efficiency of encapsulation. In comparison to b-cyclodextrin and xanthan, a higher encapsulation efficiency was observed when the chitosan was used for microencapsulation of gallic acid (da Rosa et al., 2013). In addition, microencapsulation did not affect the antioxidant capacity of gallic acid. Encapsulation of purified methanolic extract from H. perforatum leaves and flowers in becyclodextrin by freeze-drying improved the thermal stability of flavonoids. The presence of antioxidants in extracts suggested that the be cyclodextrin cavity could protect heat sensitive compounds (Kalogeropoulos, Yannakopoulou, Gioxari, Chiou, & Makris, 2010). In another study, it was shown that the encapsulation technique and the carrier materials did not affect the stability of the BACs, with special reference to the
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aqueous extracts of Piper sarmentosum, encapsulated by absorption in Ca-alginate hydrogel beads (Chan, Yim, Phan, Mansa, & Ravindra, 2010). The most appropriate encapsulation method is driven by the desired application in product, and it is governed by the physicochemical properties of the core material, and to a smaller extent, of the shell material (Ubbink & Kruger, 2006). Additionally, the selected methods should be capable to produce homogeneously distributed spherical capsules/spheres, with high encapsulation efficiency, high loading capacity, and with the desired release properties, as well as to be operated under mild and simple conditions and at lowered cost. Widely used encapsulation methods of BACs include spray-drying, spray cooling, freeze drying, fluid bed coating, melt injection and melt infusion, infusion, extrusion, emulsification, coacervation, crystallization, and costly methods, e.g. liposome and cyclodextrin encapsulation. Some examples of micronutrients encapsulated for food applications are presented in Table 1 (Champagne & Fustier, 2007; Kailasapathy, 2009). 5. Encapsulation of natural antioxidant and antimicrobial extracts Essential oils (EO) are complex mixtures of volatile compounds with strong antimicrobial and antioxidant properties. However, their use is somewhat limited by their fast oxidation, degradation, as well as by their low solubility in water and high volatility (Galvao et al., 2015). Recently, different reports investigated the encapsulation of EOs, with the main objectives to preserve their antimicrobial and antioxidant properties, as well as to promote their targeted action where microbial growth (aqueous phase) or oxidation processes (water-oil interfaces) take place. An encapsulation system with high functionality but also high costs is represented by liposomes. Liposomes are made of bilayers of amphiphilic molecules, such as phospholipids, with an internal hydrophilic aqueous section separated from the continuous aqueous phase. The structure of liposomes enables to encapsulate both hydrophilic molecules in the internal hydrophilic part and lipophilic particles in the bilayer. Liposomes are created through the spontaneous linkage of the amphiphilic particles in a lamellar phase, followed by its dispersion by high-intensity shearing or by evaporating the solvent (Donsì et al., 2016). Encapsulation of EOs in liposomes resulted in the enhancement of their biological activity, including the inhibition of the growth of microorganisms. For example, the encapsulation of Zataria multiflora EO into
nanoliposomes was enhanced antimicrobial activity against E. coli. (Khatibi et al., 2016; Khosravi-Darani, Khoosfi, & Hosseini, 2016). Liposomes are reported, together with inclusion complexes, to be suitable also to mask the taste of EOs with an intensive aroma that might negatively affect the sensory characteristics of the product, hence promoting the consumer acceptance. Similarly, nanocochleates, lipid based delivery systems based on a liposomal structure, owing to their degree of complexity, enable the control of different properties. For example, compared to the free thyme EO, nanocochleates based on the phosphatidylcholine, cholesterol and calcium ions enabled to maintain a high scavenging activity of the oil with the prolonged sustained release, using fully natural ingredients (Asprea, Leto, Bergonzi, & Bilia, 2017). Emulsions and nanoemulsions are heterogeneous structures made of two immiscible fluids, where one fluid is spread as droplets and stabilized by an appropriate emulsifier into the other continuous phase. Oil in water (O/W) emulsions are most important for EOs, where oil droplets are spread in a water-medium and stabilized with food-grade surfactants or biopolymers. Nanoemulsions are categorized by a submicrometric dimensions, generally below 100 nm (Donsì et al., 2016). , and Emulsions of oregano oil incorporated in chicken pate prepared by the phase inversion temperature, exhibited a significant antibacterial activity (Moraes-Lovison et al., 2017). Nanoemulsions of holy basil EO stabilized by gelatin, and further coated by palmitic acid emulsified in carboxymethyl cellulose, showed improved antioxidant and antimicrobial potential with respect to the pure EO (Ngamakeue & Chitprasert, 2016). Complex lipid-based systems (e.g. hollow solid lipid capsules) were engineered from peppermint EO by clean process from a fully hydrogenated soybean oil by an atomization of a CO2-expanded lipid mixture. Capsules presented a hollow solid-lipid structure that protected embedded oil with high loading capacity. This novel process retarded the release of the peppermint oil, maximized its loading capacity and masked its strong aroma, which was extremely important for the use in foods as an antimicrobial agent. Biopolymeric complexes and nanoparticles, using proteins or polysaccharides as carriers, generally not only exhibit an exceptional compatibility with foods, but are also able to efficiently encapsulate, protect and deliver different classes of BACs, including also those originated from EOs. The most suitable biopolymers for food applications are: (a) proteins (e.g. gelatin, soy and whey proteins, casein, and zein); and (b) polysaccharides (e.g. hydrocolloids as starch, cellulose, and others). The particle formation is
Table 1 Some examples of encapsulated micronutrients and applications in foods.a Ingredient
Encapsulation technique
Flavor, essential oils
Spray-drying
Fish oil, omega-3-oils, fatty acids Vitamins, minerals, antioxidants
Phytonutrients (lycopene, carotenoids, polyphenolic compounds, isoflavones) Enzymes Organic acids (lactic, acetic) a
Examples of applications and reasons for encapsulation
Prepared foods, microwavable foods Powdered dry mixes for easy application, chemical stability, slow release Spray-drying Milk, yogurt, infant formulae, health supplements Prevention of oxidative rancidity, targeting health benefits, taste masking Spray-drying, spray coating, fluidized bed coating, Cereal bars, biscuits, bread, fortification of milk, yogurts, yogurt drinks, cheese, liposomes, emulsion, evaporation, spray coating soya milk, cereals (folates), conditioning dough, pasta, prepared foods, table salts, dry blends Protection against oxidation, increased stability during cooking, color masking, reducing ingredient interactions Spray-drying, spray coating, fluidized bed drying, Milk beverages, soya milk, soya products, Nutraceuticals, fortified foods, supplements, coacervation, spray chilling, liposomes, fluidized Functional foods, preservatives, antimicrobials, bed coating Masking bitter taste, stabilization, improving bioavailability, targeted delivery Extrusion, emulsion Cheese Encapsulation, liposomes Accelerated cheese ripening Spray-drying Meat sausages, preservation aids, flavor modifiers, Desserts, baking mixes, pet foods, slow release during manufacture
Adapted from (Champagne & Fustier2007; Kailasapathy, 2009).
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influenced by preferred functionality, product compatibility, release properties, and general in product behavior (Donsì et al., 2016). A simple route to the encapsulation of EOs in biopolymers is the formation of inclusion complexes, exploiting the steric and hydrophobic interaction established between the hydrophobic chains of a polysaccharide and bioactive molecules. For example, encapsulated oils in hydroxypropyl-b-cyclodextrins (HPb-CD) protected them from degradation and enhanced their antioxidant and antimicrobial activity. More specifically, encapsulation of yarrow EOs by HPb-CD protected them from sunlight, and four-to eight-fold improved antibacterial activity against S. aureus and E. coli as compared to the pure yarrow oil (Rakmai, Cheirsilp, Torradondara, & Mejuto, 2017). Furthermore, HPb-CD Agrasar, Simal-Ga encapsulating the black pepper EO improved the antibacterial activity against S. aureus and E. coli (Rakmai, Cheirsilp, Mejuto, ndara, 2017). Compared to the free Torrado-Agrasar, & Simal-Ga clove EO, encapsulation in HPb-CD provided controlled release, better stability, increased bioaccessibility of total phenolics and antioxidant activity (Cetin Babaoglu, Bayrak, Ozdemir, & Ozgun, 2017). The encapsulation of saffron EO in a complex of gum arabic and b-cyclodextrin was associated with hygroscopicity of a carrier, content of gum arabic, its loading capacity and encapsulation efficiency (Atefi, Nayebzadeh, Mohammadi, & Mortazavian, 2017). However, in comparison with other encapsulating systems, the loading capacity of inclusion complexes is low (generally 1:1 M ratio with the payload molecule), whereas the cost of the material is high. Chitosan nanocapsules prepared by emulsion-gelation (i.e. emulsion templating, followed by chitosan gelation), when used to encapsulate thyme EO, resulted with higher radical scavenging activity vs. free thyme oil (Ghahfarokhi, Barzegar, Sahari, & Azizi, 2016). Chitosan nanocapsules loaded with cardamom EO were effective in vitro for controlling the multidrug resistant E. coli and Methicillin-resistant S. aureus without no toxicity for human cells (Jamil et al., 2016). In vitro tests showed that microencapsulated thyme EO inhibited the growth of different microorganisms (Gonçalves et al., 2017). In addition to being an excellent biopolymer carrier for EO, chitosan also possesses an intrinsic antimicrobial activity (Donsì, Marchese, et al., 2015; Severino et al., 2014). Moreover, it can be economically obtained from the waste shells of crayfish, hence reducing the costs of encapsulation. Spray-drying is a simple and inexpensive process useful to encapsulate EOs. Firstly, the EOs are emulsified in an aqueous solution with a biopolymer, able to form a glassy material during drying. Fine droplets of the emulsion are sprayed in a drying chamber and dried upon contact with a co-current/counter-current stream of hot gas, thus creating small particles, subsequently collected in a cyclone or a filter cloth. Rosemary EO was encapsulated by spray-drying preserved the original chemical profile evaluated by the major compounds. The oil proved to be a potent biopreservative that inhibited the growth of microorganisms and extended the shelf-life of Minas frescal cheese (Fernandes et al., 2017). The use of blended materials, such as gum arabic in combination with maltodextrins or inulin, deposited on the oil droplets via homogenization/ultra-sonication, resulted in a matrix structure for the efficient encapsulation of ginger EO. The presence of maltodextrins improved the encapsulation efficiency, while the presence of inulin decreased it (Fernandes et al., 2016). Coriander EO were encapsulated by spray-drying and chitosan, alginate and inulin. Emulsions with EO were prepared through ultra-sonication. The system properties were investigated by
combining different encapsulating materials, with specific reference to the viscoelastic properties, electrostatic interaction, encapsulation efficiency, wettability, and rehydratability of the microcapsules. Encapsulated coriander oil displayed a resistance to pH and temperature variations, and enabled a delayed release of tras¸cu, Cantaragiu, Alexe, & Dima, 2016). Duman the oil (Dima, Pa and Kaya (2016), who encapsulated coriander oil via spray drying using chitosan as a carrier, observed a high antioxidant/antimicrobial activity of the capsules (Duman & Kaya, 2016). Rosmarinic acid is polyphenolic compound commonly found in plants with significant antioxidant, anti-carcinogenic, and antiinflammatory activities. It has poor solubility and low partition coefficient in water and limited transport across biological barriers. This can be overcome by encapsulation in modified chitosan microparticles and by a spray-drying (Casanova, Estevinho, & Santos, 2016). Researchers obtained products with 42.6% and 39.8% of chitosan and modified chitosan particles as encapsulating agent respectively, their average diameter was 4.2 mm and 7.7 mm. Controlled release of modified chitosan particles showed slower release of rosmaric acid in oil than in water. Encapsulation via the electrospun nanofibrous film is a promising method for a high continuous production and easy processing (Kayaci & Uyar, 2012). Produced under optimal conditions, electrospun polyvinyl alcohol/ cinnamon EO/b-cyclodextrin nanofibrous films with smooth and uniform nanofibers were able to retain the EOs in the nanofilm. The nanofibrous film with cinnamon oil resulted with an improved thermal stability and antimicrobial activity that extended the shelflife of strawberry which was used for testing (Wen et al., 2016). Oleuropein obtained from olive leaf extracts is a polyphenolic compound with the strong antioxidant property (Putnik, Barba, et al., 2017). Mourtzinos, Salta, Yannakopoulou, Chiou, and Karathanos (2007) improved water solubility of oleuropein and protection from oxidative decomposition by its inclusion in the cavity of b-CD at a 1:1 ratio. Moreover, they proposed that the solid complex obtained from freeze-drying is useful as stable food ingredient (Mourtzinos et al., 2007). 6. Encapsulation of volatile compounds Volatile organic compounds are defined as organic chemicals with vapor pressure above 10 Pa (at 25 C), a boiling point below 260 C (at atmospheric pressure), and less than 15 carbon atoms (Williams & Koppmann, 2007). Most food aromas and flavors fall in this group of compounds. Being highly volatile and reactive, aromas and flavors are easily dispersed or degraded during food production, storage, and preparation. The design and engineering of encapsulation systems for aromas and flavors in food production are very challenging, as they aim primarily at the retention/preservation and controlled release of such highly volatile molecules during storage, preparation, and consumption of foods. Therefore, encapsulating systems should protect aromas and flavors against deterioration, including evaporation out of the product caused by diffusion. Moreover, they should prevent unwanted mixing and degradation of the compounds resulted from oxidation and hydrolysis, which may form undesired off-flavors (Lamprecht & Bodmeier, 2012; Winkel, 2009). Controlled release of volatile compounds depends on diffusion of the component through the matrix, relocation from the matrix to the surroundings, particle size and geometry, and deterioration of the wall material (Madene, Jacquot, Scher, & Desobry, 2006). Various parameters influence the discharge of the encapsulated substance, for instance changes in pH, temperature, mechanical stress, enzymatic activity and the presence of solvents. Core material diffusion is influenced by the wall material nature, morphology, and elastic modulus of the polymer. The most
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common method of controlled release in the food industry involves activation by solvent, thus, active components can be released from microcapsules in various products from direct contact with aqueous media (Gibbs, Kermasha, Alli, & Mulligan, 1999). To enable controlled retention and release of volatiles, the properties of the encapsulation systems can be tailored by controlling the wall materials and the production factors (Madene et al., 2006; Naknean & Meenune, 2010). In particular, the structuring of the wall material is the central determining factor for functional features of the microcapsule. Usually, volatiles are encapsulated inside of a solid matrix (e.g. food-approved carbohydrates, fats, proteins or sugars), which may or may not be chemically modified. Different wall materials are commonly combined or added with modifiers, for example antioxidants, surfactants, oxygen scavengers, or chelating agents. Various techniques are currently available for the inclusion of volatiles in microcapsules, such as extrusion; coacervation; spray -drying, -chilling ecooling; formation of inclusion complexes, use of supercritical fluids, co-crystallization and fluidized bed coating. However, the main commercial microencapsulation techniques used in the food industry are spray-drying and extrusion (Byun, Kim, Desai, & Park, 2010). One of the volatile organic compounds, whose preservation has challenged the food industries in the last decades, is citral. Citral is a lemon-like aroma compound, which finds several applications in the food and drink industry. However, citral is highly susceptible to degradation and subsequent formation of off-flavors, such as p-cymene, p-cresol and p-methylacetophenone, when stored at low pH or in an oxidative environment (Tian et al., 2017), which are typical conditions of carbonated beverages. Citral preservation from degradation in acidic liquids is reported to be promoted when encapsulated in emulsions with suitable wall materials, which reduce its diffusion to the droplet interfaces (Choi, Decker, Henson, Popplewell, & McClements, 2010; Djordjevic, Cercaci, Alamed, McClements, & Decker, 2008), especially when using multiple biopolymer layers (Yang, Tian, Ho, & Huang, 2012). Carbohydrates and proteins are the principal classes of matrix materials suitable for the encapsulating aromas and flavors, thanks to their availability, diversity, low costs and ability to interact with the payload compounds. Besides, these encapsulation materials have other interesting properties, such as good water solubility and low viscosity, which are of paramount importance for spray-drying processes. On the other hand, the principal disadvantage for the most of the carbohydrates as encapsulating materials is their low emulsifying capacity and low volatile retention (Botrel, de Barros Fernandes, & Borges, 2015). Milk proteins (e.g. whey protein concentrate and caseinates) have been widely studied for encapsulation of volatile compounds. They are amphiphilic molecules able to form micelle systems and useful carriers for lipophilic constituents (Marques, 2010). These proteins absorb and reorganize their structure at the oil water interface during the emulsification and contribute to stabilizing the emulsions by the repulsive forces (Jafari, Assadpoor, He, & Bhandari, 2008). Encapsulation efficiency may be increased through the selection of wall materials with different functional properties. Replacement of whey concentrate with carbohydrate surface-active groups increased the volatiles retention in the encapsulation of caraway EO €, Rimantas Venskutonis, & during spray-drying (Bylaite €, 2001). Whey protein isolates are good blockage of Maþdþieriene orange oil oxidation (Kim & Morr, 1996), that effectively entrapped volatiles during spray-drying. Whey protein-carbohydrate blends are effective carrier matrices. For example, ethyl butyrate and ethyl caprylate were successfully (micro)encapsulated with wall systems, formulated
7
with sole whey proteins or equal shares of whey protein and lactose (1:1) (Rosenberg & Sheu, 1996; Sheu & Rosenberg, 1995). Retention of the volatile esters was strongly influenced by their initial load, wall type, and wall solids concentration. The mixture was more effective than sole whey proteins. During spray-drying, mixtures of proteins and high carbohydrate dextrose equivalents had fewer ruptures of microcapsules than mixtures with a lower dextrose equivalents (Sheu & Rosenberg, 1998). It was reported that the absence of surface cracks is crucial for maximizing the protection of the core materials and associated losses of the encapsulated components during storage. Starch has limited use as a microencapsulation agent due to low solubility in water, so its chemical structure is often modified, principally by chemical and physical processes. In order to emulsify volatile molecules, it is necessary to have lipophilic and hydrophilic groups in the encapsulating polymer. Starch partially hydrolyzed with octenyl succinic anhydride gains a hydrophobic octenyl chains and forms an amphiphilic molecule. This small number of substitutions gives a product with excellent volatile retention and stable emulsions for spray-drying (Shahidi & Han, 1993; €fer, & Gilbert, 2013). A key modification Sweedman, Tizzotti, Scha of starch for flavor control is the formation of amylose inclusion complexes with volatiles, particularly small nonpolar components (Jouquand, Ducruet, & Giampaoli, 2004; Nuessli, Putaux, Bail, & on, 2003). Bule Starchearoma complexes can be used to control the discharge of flavors during simulated eating. Furthermore, engineered corn starch-menthol inclusion complexes stabilized the aroma over extended storage while providing immediate release of volatiles from the matrix with modal-salivary solution triggered by enzymatic digestion (Ades, Kesselman, Ungar, & Shimoni, 2012). D-limonene encapsulated with modified starch, gum arabic, and maltodextrin as the matrix, was tested for oxidative stability after spray-dying (Soottitantawat et al., 2005). Furthermore, cardamom oleoresin was spray-dried and encapsulated with the same combination of wall materials for resistance to light-sensitivity, heat, and oxidation of oleoresins (Krishnan et al., 2005). Jouquand et al. (2004) reported preservation of flavor compounds encapsulated by modified polysaccharide as a function of temperature (Jouquand et al., 2004). Maltodextrins solution increased the retention of the flavor with increased temperature and depended on hydrophobicity (Jouquand et al., 2004). In a different report, the flavor release of maltodextrin, gum arabic and soy powders was studied as a function of time and humidity (Yoshii et al., 2001). Results showed that the release of ethyl butyrate decreased with increased concentration of maltodextrin in the feed liquid. Manojlovi c et al. (2008) studied the development of flavor (ethyl vanillin) in alginate formulations in thermally processed foods (controlled release under heating) by electrostatic extrusion (Manojlovic et al., 2008). Boland et al. explored the release of 11 flavors from gels made of gelatin, starch and pectin with the conclusion that the flavor release was mainly influenced by the texture of the gels (Boland, 2004). Previous reports emphasized the importance of wall material properties for the study reported controlled preservation of aromas and flavors; however, the processing conditions are another important factor to consider. In this sense, a significant challenge is to engineer microcapsules that are able to resist harsh processing conditions. For instance, Fernandes et al. (2013) observed in microencapsulation of rosemary oil by spray-drying with maltodextrins and modified starch as wall materials, that there were no significant changes in the profile of principal components of the oil under high inlet temperature of air was 190 C (Fernandes et al., 2013). Adamiec and Kalemba (2006) engineered spray-dried microcapsules with maltodextrin and peppermint oil that was well
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preserved under air-drying at 150 C (Adamiec & Kalemba, 2006). Freeze-drying was identified as a sensitive and simple encapsulation method (Laine, Kylli, Heinonen, & Jouppila, 2008), appropriate for heat-sensitive materials, including volatiles, since dehydration is conducted subsequent to freezing and at low temperatures with vacuum (not like the spray-drying that is done at elevated temperatures). The key drawbacks of the freeze-drying include expensiveness and lengthy dehydration (Shahidi & Han, 1993). Another effective technique for encapsulating volatile compounds is the inclusion in b-cyclodextrins. Petrovi c, Stojanovic, and Radulovi c (2010) reported the addition of cinnamon oil complexes flavors with b-CD, as a function of different oil to b-cyclodextrins ratios, and revealed the strongest retention of volatiles was with 1:9 oil to b-CD ratio (Petrovi c et al., 2010). Eugenol is polyphenol and a major flavor component of nutmeg, clove, basil, and cinnamon EOs. In a study of eugenol addition to b-CD or 2-HPb-CD, better encapsulation of eugenol and corresponding light-oxidative stability was detected with b-CD vs. 2-HPb-CD. Authors proposed that hydroxypropyl side chain of 2-HPb-CD hinders addition of eugenol in the cavity of the cyclodextrin particle (Choi, Soottitantawat, Nuchuchua, Min, & Ruktanonchai, 2009). A different study reported controlled the discharge of antifungal volatile particles of thyme EO from b-CD microcapsules. The extent of the controlled release of the encapsulated compounds correlated well with the high relative humidity of the environment, peaking at nchez et al., 100% relative humidity with 76% release (Del Toro-Sa 2010). Reineccius, Reineccius, and Peppard (2002) documented the retention of various flavor compounds during the encapsulation with a-, b-, and g-cyclodextrins. Here, cyclodextrins stabilized several unstable flavor molecules, where a- and b-cyclodextrins showed the best withholding for the duration of spray-drying and storage (Reineccius et al., 2002). 7. Innovative strategies and non-conventional methods for encapsulation of natural extracts Development and design of new foods is a very expensive undertaking for the industry (Musina et al., 2017). Chemat et al. (2017) recently reviewed several innovative food-processing techniques in connection with their role in promoting a more sustainable food manufacturing (Chemat et al., 2017). Techniques, such as microwave, ultrasound, pulse electric field, instant controlled pressure drop, supercritical fluid processing, are considered at the frontiers of food processing, food chemistry, and food microbiology, and are become a hot research topic for the design of green and sustainable processes for the food industry. However, most of them are not new, as they were already used for >30 years by academia and industry. What is new, is the concept of Green Food Processing, developed to meet the economic, societal and environmental challenges of the 21st century, and hence to safeguard the environment and consumers, respectively. Plus, to drive industrial competition to be more ecologic, profitable, and innovative. This green scheme should include entire value-chain with both the economic and accountability aspects, starting from the manufacturing and harvesting of food raw materials, and ending up with the processes of preservation, transformation, and extraction, as well as including formulation and marketing (Chemat et al., 2017). Within this frame, encapsulation, both at the microscopic and nanoscopic levels, represents a great challenge, because of its high capital and operating costs, and the requirement for complex processing equipment and, sometimes, organic solvents. Therefore, the innovative strategies and non-conventional methods for encapsulation of natural extracts in the next years should rather address the Green Food Processing concept, differently from other
fields, such as the pharmaceutical one, where the biological performance (i.e. the capability to deliver the payload molecules across the biological barriers) is the primary driving force. Within this picture, nanoencapsulation has gathered increasing interest for the formation at the nanometric scale of food-grade particles or emulsion droplets with functional features, containing encapsulating matrix (naturally-derived compounds, such as carbohydrates, proteins, and lipids) and an active substance (natn, Silva, & ural extracts) spread inside the systems (Osorio-Tobo Meireles, 2016). The incorporation of BACs in food products using nanoscale delivery systems may offer extra health benefits, in addition to providing protection against undesired environmental conditions (e.g., heat, light and oxygen). For example, nanoencapsulation contributes to improving the bioavailability of the payload compounds, while enabling their controlled release and target delivery. The nanoencapsulation of flavors (e.g. EOs from leaves, fruits, and seeds) is an appealing concept able to bring important innovations in the food manufacturing. The EOs encapsulation in natural delivery systems can be exploited as a natural strategy to improve microbial safety, and fresh-like organoleptic properties of food. In particular, nanoemulsions have perspective benefits over common emulsions thanks to their large active surface area, small mean particle size, and limited susceptibility to physical destabilization. In foods with microorganisms, nanoemulsions foster usage of EOs by improving their dispersibility and the negative impact on the quality, and at the same time improve antimicrobial activity in products (Donsì & Ferrari, 2016). Encapsulating systems deliver and control the release of BACs in foods, prevent degradation with the improvement of their solubility. Ozogul et al. (2017) recently studied the antimicrobial and antioxidant effects of nanoemulsions containing herbal oils (rosemary, laurel, thyme, and sage) on the quality of rainbow trout. Fish fillets were immersed for 3 min in the nanoemulsions prepared with different oils. Nanoemulsions of essential oils enhanced the organoleptic quality of rainbow trout with a shelf-life increase from 14 days (controls) to 17 days (treatment groups). The lowest bacterial counts were obtained for rosemary and thyme EOs. The use of EOs also slowed down the lipid oxidation in the fish (Ozogul et al., 2017). High methoxyl pectin and a non-ionic surfactant stabilized (Tween 80) nanoemulsions (all droplet sizes were 90%) with enhanced controlled release, caused by their restraint in a solid lipid matrix (Donsì et al., 2016). SLN consist of lipid droplets spread in a water-phase and stabilized by an emulsifier, with the lipids being fully or partially solidified (Donsì, Sessa, & Ferrari, 2015). Campos, Madureira, Sarmento, Gomes, and Pintado (2015) investigated the use of SLN to deliver extracts rich in phenolic compounds. Two types of lipids (Witepsol and carnauba waxes) were loaded with sage and savory extracts. Simulated digestion experiments showed that under gastric conditions only a partial release of the encapsulated compounds occurred whereas under small intestinal conditions, a complete release was observed. Moreover, Witepsol-based SLN were the most stable vehicles for sage and savory extracts, maintaining their physical integrity, and the antioxidant activity of the encapsulated compounds, during digestion (Campos et al., 2015). Another innovative strategy for encapsulating natural extracts consists in combining encapsulation with extraction based on alternative technologies; possibly to reap benefits of such combination in terms of lower energy consumptions and better preservation of the extracts. An example is the combination of supercritical fluid extraction (SFE) with ultrasonication to engineer nanoparticles/nanoemulsions with EOs for the use as flavors and aromas in foods, hence providing added value to the foods with promoting innovative industrial production (de Souza Sim et al., n et al., 2016). 2017; Osorio-Tobo The SFE was also tested for pink pepper (Schinus terebinthifolius R.) fruits to recover phenolic compounds with high antioxidant activity. The SFE performed at pressures from 150 to 300 bars and temperatures of 40, 50 and 60 C, with CO2 as a solvent. The subsequent encapsulation process was conducted through emulsification and solvent extraction, using PLA as encapsulating agent (Andrade, Poncelet, & Ferreira, 2017). The obtained micrometric size particles with spherical shape and morphology exhibited an encapsulation efficiency ranging from 34.3% to 74.1% (Andrade et al., 2017). Another possibility is the combination of the ultrasoundassisted extraction (UAE) of polyphenols and their subsequent encapsulation by spray-drying. This approach was applied for the exploitation of pomegranate peel extracts in the food industries (Kaderides, Goula, & Adamopoulos, 2015). Ultrasound treatment increased the extraction yield and shortened the process for more than 20 fold. Very high encapsulation efficiency (99.80%) reported when maltodextrin/whey protein isolate (50:50 ratio) were used as wall material. Ratio of wall-to-core-material was 9:1 and a feed solid concentration was 30% (w/w). The encapsulated phenolic extracts efficiently improved the shelf-life of hazelnut paste
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(Kaderides et al., 2015). Different ultrasound emulsification parameters (ultrasound power, the concentration of surfactant, oil-to-water ratio and their influence on emulsion droplet size), were investigated to encapsulate capsaicinoids recovered by SFE from Capsicum frutescens pepper. Emulsions in a SFE process were formed with oleoresin and by using Hi-Cap 100 as a stabilizer. Emulsification had high efficiency and stability, while selected time for the injection into the SFE was 10 min following the preparation, based on the coalescence kinetics. Oleoresin was significantly lost in the SFE due to dissolution with supercritical CO2. Further, it expanded the droplet volume, detected by the increase in the diameter of the droplets in suspension (Aguiar, Silva, Rezende, Barbero, & Martínez, 2016). The UAE was coupled with a single stage cyclodextrins inclusion with extracts of resveratrol and other polyphenols recovered from Polygonum cuspidatum (Mantegna et al., 2012). Fine milled roots were sonicated in methanol (titanium horn, 19.5 kHz), with different cyclodextrin aqueous solutions (b-CD or HPb-CD). UAE strongly improved the yields with a decrease of extraction length as compared to the stirred conventional extraction, enabling the simultaneous inclusion in b-CD (solution at 1.5% w/w). In particular, b-CD enabled the selective inclusion of phenolic stilbenes, especially resveratrol. The polyphenols, encapsulated within CDs, were well dispersed in water, had high stability and an antioxidant potential, that was comparable to the MeOH extracts (Mantegna et al., 2012). Silva, Zabot, Angela, and Meireles (2015) encapsulated annatto seed oil (rich in geranyl geraniol) extracted by high intensity ultrasound and with gum arabic as a stabilizing agent. The best emulsion was obtained by freeze-drying and spray-drying. Emulsions exposed to a combined increase of ultrasound power and time had lower polydispersity and superficial mean diameter. Spray-drying generated microparticles with the highest encapsulation efficiency of 85.1 % wt. Freeze-dried microparticles prepared with gum arabic efficiently entrapped the oil (97 ± 1 wt.%) with a geranyl geraniol retention of 80e86 wt.% (Silva et al., 2015). Electrohydrodynamic atomization (EHDA) was used for encapsulation of curcumin in gelatin. Round gelatin particles (with a diameter ranging from a few nanometers to > 1 mm) were loaded with 10% (w/w) curcumin at 100% encapsulation efficiency. Curcumin was 39 times more water soluble when encapsulated in the gelatin microparticles. It was proved that the encapsulation of curcumin in gelatin particles by EHDA greatly improved its anti mez-Estaca, Balaguer, oxidant and antimicrobial properties (Go pez-Carballo, Gavara, & Hern ~ oz, 2017). Lo andez-Mun 8. Conclusions Encapsulation is a site or speed specific technology able to stabilize and control the release of encapsulated material, i.e. highadded value biological compounds (BACs) from herbs and other matrices. BACs, such as essential oils, vitamins, proteins, minerals, antioxidants etc., provide nutritive and medicinal properties such as anti-inflammatory, anti-allergic, antibacterial and antiviral protection. However, the BACs are sensitive and easily degraded by the environmental stresses (exposure to oxygen, water, light etc.), to which they are exposed during processing and storage. Encapsulation provides protection, delivery, taste masking and controlled release of BACs, enabling their use in the production of nutraceuticals, food additives, and supplements. Encapsulated material is generally released by diffusion, dissolution, erosion, digestion, mechanical disruption, and is triggered by temperature, pH, pressure, and ionic force. The most common encapsulation methods of BACs include spray-drying, spray cooling, freeze drying, and others. Spray-drying is a simple and inexpensive technology useful to
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encapsulate essential oils (EO) in a matrix-type, micrometric encapsulation system, upon drying at high temperature. However, the increasing consumers' and manufacturers’ demands towards increased functionality drive the research towards innovative processes, which enable a better preservation of the healthbeneficial properties of BACs, the improved compatibility with food systems, the enhanced bioaccessibility, taste masking, as well as the use of natural ingredients. Moreover, also the Green Food Processing concept pushes towards innovation to further reduce the manufacturing costs, improve the scalability as well as to reduce the use of organic solvents. Therefore, several encapsulation methods have been proposed, which, either through the nanoscale manufacture (i.e. nanoemulsions, and solid lipid nanoparticles), or the direct coupling with novel extraction techniques (supercritical fluid or ultrasound assisted extraction), enable to pursue these ambitious objectives. Acknowledgments Authors would like to acknowledge the Croatian Science Foundation for their financing of the project titled “High voltage discharges for green solvent extraction of bioactive compounds from Mediterranean herbs (IP-2016-06-1913)”. We thank Sandra Berak and Ivica Raljevic for donating photographs of Mediterranean plants. All authors declare no conflict of interest. References Adamiec, J., & Kalemba, D. (2006). Analysis of microencapsulation ability of essential oils during spray drying. Drying Technology, 24, 1127e1132. Ades, H., Kesselman, E., Ungar, Y., & Shimoni, E. (2012). Complexation with starch for encapsulation and controlled release of menthone and menthol. LWT - Food Science and Technology, 45, 277e288. Aguiar, A. C. d., Silva, L. P. S., Rezende, C. A. d., Barbero, G. F., & Martínez, J. (2016). Encapsulation of pepper oleoresin by supercritical fluid extraction of emulsions. The Journal of Supercritical Fluids, 112, 37e43. Alvim, I. D., Prata, A. S., & Grosso, C. R. F. (2017). Methods of encapsulation. In M. P. M. Garcia, M. C. Gomez-Guillen, E. Lopez-Caballero, & G. V. BarbosaCanovas (Eds.), Edible films and coatings. Fundamentals and applications (pp. 299e315). Taylor&Francis Group: CRC Press. Andrade, K. S., Poncelet, D., & Ferreira, S. R. S. (2017). Sustainable extraction and encapsulation of pink pepper oil. Journal of Food Engineering, 204, 38e45. Asprea, M., Leto, I., Bergonzi, M. C., & Bilia, A. R. (2017). Thyme essential oil loaded in nanocochleates: Encapsulation efficiency, in vitro release study and antioxidant activity. Lwt-food Science and Technology, 77, 497e502. Atefi, M., Nayebzadeh, K., Mohammadi, A., & Mortazavian, A. M. (2017). Using Bcyclodextrin and Arabic gum as wall materials for encapsulation of saffron essential oil. Iranian Journal of Pharmaceutical Research, 16, 93e102. Barba, F. J., Esteve, M. J., & Frígola, A. (2014). Bioactive components from leaf vegetable products. In Atta-ur-Rahman (Ed.), Studies in natural products chemistry ((1st ed.), Vol. 41, pp. 321e346). Elsevier. Barba, F. J., Galanakis, C. M., Esteve, M. J., Frigola, A., & Vorobiev, E. (2015). Potential use of pulsed electric technologies and ultrasounds to improve the recovery of high-added value compounds from blackberries. Journal of Food Engineering, 167, 38e44. Barba, F. J., Zhu, Z., Koubaa, M., de Souza Sant'Ana, A., & Orlien, V. (2016). Green alternative methods for the extraction of antioxidant bioactive compounds from winery wastes and by-products: A review. Trends in Food Science & Technology, 49, 96e109. Bels cak-Cvitanovi c, A., Stojanovi c, R., Manojlovi c, V., Komes, D., Cindri c, I. J., Nedovi c, V., et al. (2011). Encapsulation of polyphenolic antioxidants from medicinal plant extracts in alginateechitosan system enhanced with ascorbic acid by electrostatic extrusion. Food Research International, 44, 1094e1101. Boland, A. (2004). Influence of gelatin, starch, pectin and artificial saliva on the release of 11 flavour compounds from model gel systems. Food Chemistry, 86, 401e411. Botrel, D. A., de Barros Fernandes, R. V., & Borges, S. V. (2015). Microencapsulation of essential oils using spray drying technology. In L. M. Sagis (Ed.), Microencapsulation and microspheres for food applications (pp. 235e251). Elsevier Inc. Bursa c Kova cevi c, D., Putnik, P., Pedisi c, S., Je zek, D., Karlovic, S., & DragovicUzelac, V. (2015). High hydrostatic pressure extraction of flavonoids from freeze-dried red grape skin as winemaking by-product. Annals of Nutrition and Metabolism, 67, 521e522. €, E., Rimantas Venskutonis, P., & Maþdþieriene €, R. (2001). Properties of Bylaite caraway ( Carum carvi L.) essential oil encapsulated into milk protein-based matrices. European Food Research and Technology, 212, 661e670.
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