Nanoencapsulation Techniques for Food Bioactive

Food Bioprocess Technol DOI 10.1007/s11947-012-0944-0

REVIEW PAPER

Nanoencapsulation Techniques for Food Bioactive Components: A Review P. N. Ezhilarasi & P. Karthik & N. Chhanwal & C. Anandharamakrishnan

Received: 15 March 2012 / Accepted: 23 July 2012 # Springer Science+Business Media, LLC 2012

Abstract The protection and controlled release of bioactive compounds at the right time and the right place can be implemented by encapsulation. Nanoencapsulation remains to be the one of the most promising technologies having the feasibility to entrap bioactive compounds. Nanoencapsulation of bioactive compounds has versatile advantages for targeted site-specific delivery and efficient absorption through cells. However, researches in the application of nanotechnology in the food industry have been very limited and there are only a few review articles that explored the nanoencapsulation technology. This review focuses on the various nanoencapsulation techniques such as emulsification, coacervation, inclusion, complexation nanoprecipitation, emulsification–solvent evaporation, and supercritical fluid for food ingredients. Drying techniques such as spray drying and freeze drying for stabilization of nanoparticles are also discussed. Current state of knowledge, limitations of these techniques, and recent trends are also discussed. Finally, safety and regulatory issues in the nanoencapsulation of bioactive compounds are also highlighted. Keywords Nanoencapsulation . Bioactive compounds . Nanoemulsions . Biopolymers . Drying techniques

Introduction Nature had created the building blocks of life in nanoscale such as DNA, amino acids, sugars, and hormones (Weiss et al. 2006). Inspired by nature’s creation, man had engineered P. N. Ezhilarasi : P. Karthik : N. Chhanwal : C. Anandharamakrishnan (*) Human Resource Development, CSIR—Central Food Technological Research Institute, Mysore 570 020, India e-mail: [email protected]

nanomaterial for the progress and prosperity of mankind. In 1959, Richard Feynman proposed the concept of nanostructures, and in 1974, Nario Taniguchi coined the term nanotechnology for manipulation of submicron particles. The term “nano” refers to a magnitude of 10−9 m (QuintanillaCarvajal et al. 2010). British Standards Institution defined nanotechnology as the design, characterization, production, and application of structures, devices, and systems by controlling the shape and size at the nanoscale (Bawa et al. 2005). Nanotechnology has emerged as one of the most promising scientific fields of research in decades. It deals with the production, processing, and application of materials with sizes less than 1,000 nm (Sanguansri and Augustin 2006). Reduction in particle size to nanoscale range increases surface-to-volume ratio, which consecutively increases their reactivity by many folds with change in mechanical, electrical, and optical properties. These properties offer many unique and novel applications in various fields (Neethirajan and Jayas 2010). For example, silicon chips have been made by nanotechnology for over 20 years. It leads to advances in electronics, computing, and communications, which revolutionized the world and changed the horizons of human life. Nanotechnology has been touted as the next revolution in many industries, including agriculture and food industry. Nanotechnology has been revolutionizing the entire food system from production to processing, storage, and development of innovative materials, products, and applications. The application of nanotechnology to the food sector could generate innovation in the macroscale characteristics of food, such as texture, taste, other sensory attributes, coloring strength, processability, and stability during shelf-life, leading to a great number of new products. Moreover, nanotechnology can also improve the water solubility, thermal stability, and oral bioavailability of bioactive compounds (Huang et al. 2010; McClements et al. 2009; Silva et al. 2012). At present, applications of nanotechnology in food

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industries are nanocomposites in food packaging material for controlling diffusion and microbial protection, nanobiosensors for detection of contamination and quality deterioration, and nanoencapsulation or nanocarrier for controlled delivery of nutraceuticals (Chen et al. 2006a; Sanguansri and Augustin 2006; Sozer and Kokini 2009; Weiss et al. 2006). Currently, the market of nanotechnology products in the food industry approaches US$1 billion (most of this on nanoparticle coatings for packaging applications, healthpromoting products, and beverages) and it has the potential to grow to more than US$20 billion in the next decade (Chau et al. 2007). Many reviews and research papers have been published on the application of nanotechnology in foods (Weiss et al. 2006; Sekhon 2010; Neethirajan and Jayas 2010; Sozer and Kokini 2009; Graveland-Bikker and De Kruif 2006; Sanguansri and Augustin 2006; Silva et al. 2012). However, only few works were focused on nanoencapsulation of food ingredients (Quintanilla-Carvajal et al. 2010; Augustin and Hemar 2009; Mozafari et al. 2006; Fathi et al. 2012). Therefore, the main aim of this review is to discuss the various nanoencapsulation techniques and their advantages, flaws, and variations, as well as to appraise the interesting emerging technologies and trends in this field along with regulatory issues. In this way, we had analyzed the research tendency in these encapsulation techniques since year 2000 until now.

Nanoencapsulation Encapsulation is a rapidly expanding technology with a lot of potential applications in areas including pharmaceutical and food industries. It is a process by which small particles of core materials are packed within a wall material to form capsules. Encapsulation method was employed to protect bioactive compounds (polyphenols, micronutrients, enzyme, antioxidants, and nutraceuticals) and in the finished application to protect them from adverse environment and also for the controlled release at targeted sites (Gouin 2004). Microcapsules are particles having a diameter between 3 and 800 μm (Meena et al. 2011). Nanoparticles are colloidal-sized particles with diameters ranging from 10 to 1,000 nm and are expressed both as nanocapsules and nanospheres (Konan et al. 2002). Nanocapsules are vesicular systems in which the bioactive compound is confined to a cavity surrounded by a unique polymer membrane, while nanospheres are matrix systems where the bioactive compound is uniformly dispersed (see Fig. 1) (Couvreur et al. 1995) Nanoencapsulation is defined as a technology to encapsulate substances in miniature and refers to bioactive packing at the nanoscale range (Lopez et al. 2006). The delivery of any bioactive compound to various sites within

(a) Nanocapsules Bioactive compound

(b) Nanospheres Polymer or lipid or other wall material

Fig. 1 Schematic structure of a nanocapsules and b nanospheres (Orive et al. 2009)

the body is directly affected by the particle size (Kawashima 2001; Hughes 2005). Thus, nanoencapsulation has the potential to enhance bioavailability, improve controlled release, and enable precision targeting of the bioactive compounds in a greater extent than microencapsulation (Mozafari et al. 2006). Wall and Core Materials Used for Nanoencapsulation Nutraceuticals are used in foods to impart health benefits. The effectiveness of nutraceuticals in preventing disease depends on preserving the bioavailability of bioactive ingredients until their release at targeted sites (Chen et al. 2006a). Reducing the particle size may improve the bioavailability, delivery properties, and solubility of the nutraceuticals due to more surface area per unit volume and thus their biological activity (Shegokar and Muller 2010). The bioavailabilities of these nutraceuticals are increased as a nanocarrier allows them to enter the bloodstream from the gut more easily. The nanoscale nutraceuticals were coined together as “nanoceutical” and carriers were called nanocarriers due to their size (Chen et al. 2006a). These nutraceutical compounds can be classified into lipophilic and hydrophilic types based on their solubility in water. Hydrophilic compounds are soluble in water but insoluble in lipids and organic solvents. Some of the nanoencapsulated hydrophilic nutraceuticals are ascorbic acid, polyphenols, etc. (Lakkis 2007; Teeranachaideekul et al. 2007; Dube et al. 2010; Ferreira et al. 2007). Lipophilic compounds are insoluble in water but soluble in lipids and organic solvents. Nanoencapsulated lipophilic nutraceuticals include lycopene, beta-carotene, lutein, phytosterols, and docosahexaenoic acid (DHA) (Lakkis 2007; Heyang et al. 2009; Zimet and Livney 2009; Leong et al. 2011). The solubility of the bioactive ingredients determines the release rate and release mechanism from a polymeric matrix system. Hydrophilic compounds show faster release rates and their release kinetics is determined by the appropriate combination of diffusion and erosion mechanisms. Lipophilic compounds often

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resulted in incomplete release due to poor solubility and low dissolution rates by an erosion mechanism (Kuang et al. 2010; Kumar and Kumar 2001; Varma et al. 2004). However, lipophilic compounds are highly permeable through the intestine via active transport and facilitated diffusion, whereas hydrophilic compounds have low permeability and are absorbed only by active transport mechanism (Acosta 2009). Nanocarrier food systems such as lipid or natural biodegradable polymer-based capsules are most often utilized for encapsulation (Chen et al. 2006a). Nanoliposomes, archaeosomes, and nanocochleates are three types of lipid-based nanocarrier systems with application in pharmaceutical, cosmetic, and food industries. Natural polymers such as albumin, gelatin, alginate, collagen, chitosan, and α-lactalbumin were used for the formulation of nano delivery systems (Reis et al. 2006; Graveland-Bikker and De Kruif 2006). There is tremendous growth observed in the development of food nanocarrier system in the last decade such as various products developed like whey protein which is used as nanocarrier to improve the bioavailability of nutraceuticals, nanodrops mucosal delivery system of vitamins, and nanobased mineral delivery system (Chen et al. 2006a, b).

Nanoencapsulation Techniques In general, the physicochemical properties such as particle size, size distribution, surface area, shape, solubility, and encapsulation efficiency, and releasing mechanisms were reported to be altered by the encapsulation technique and delivery system. Therefore, it is more essential to select the appropriate encapsulation technique based on the required size, physicochemical properties, nature of the core material, and wall material. Moreover, the techniques used for achieving nanoencapsulation are more complex than microencapsulation. It is mainly due to the difficulty in attaining a complex morphology of the capsule and core material and the demands of releasing rates of nanoencapsulates (Chi-Fai et al. 2007). Various techniques have been developed and used for microencapsulation purpose. However, emulsification, coacervation, inclusion complexation, emulsification–solvent evaporation, nanoprecipitation, and supercritical fluid technique are considered as nanoencapsulation techniques since they can produce capsules in the nanometer range (10–1,000 nm). Nanoencapsulation techniques use either top-down or bottom-up approaches for the development of nanomaterials. A top-down approach involves the application of precise tools that allow size reduction and structure shaping for desired application of the nanomaterials being developed. In the bottom-up approach, materials are constructed by self-assembly and self-organization of molecules, which were influenced by many factors including pH, temperature,

concentration, and ionic strength (Augustin and Sanguansri 2009). Techniques such as emulsification and emulsification–solvent evaporation are used under the top-down approach. On the other hand, supercritical fluid technique, inclusion complexation, coacervation, and nanoprecipitation are used in the bottom-up approach (as shown in Fig. 2) (Sanguansri and Augustin 2006; Mishra et al. 2010). These nanoencapsualtion techniques can be used for encapsulation of various hydrophilic and lipophilic bioactive compounds. Emulsification, coacervation, and supercritical fluid technique are used for encapsulation of both hydrophilic and lipophilic compounds (McClements et al. 2009; Chong et al. 2009; Leong et al. 2009). However, inclusion complexation, emulsification–solvent evaporation, and nanoprecipitation techniques are mostly used for lipophilic compounds (Reis et al. 2006). Table 1 and the following subsections will discuss in detail the different techniques used for the nanoencapsulation process. Emulsification Technique Emulsion technology is generally applied for the encapsulation of bioactive compounds in aqueous solutions through the production of nanoemulsions. Nanoemulsions are colloidal dispersions comprising two immiscible liquids, of which one is being dispersed in the other, with droplet sizes ranging from 50 to 1,000 nm (Sanguansri and Augustin 2006). They offer great potential to encapsulate a high concentration of oil-soluble nutraceuticals or bioactive food supplements into a wide range of foodstuffs. Lipophilic active agents such as β-carotene, plant sterols, carotenoids, and dietary fats can be encapsulated and delivered by oil in

Fig. 2 Top-down and bottom-up approaches in nanoencapsulation techniques

Nanoprecipitation

Inclusion complexation

Coacervation

Wall materials: maltodextrin; emulsifiers: modified starch (Hi-Cap 100) Emulsifiers: Tween-40

Emulsification

Wall materials: ethyl cellulose and methyl celluolose

Wall materials: monomethoxy poly (ethylene glycol)-poly (3-caprolactone) micelles Wall materials: poly (lactide-co-glycolide); emulsifiers: polyethylene glycol-5000

Wall materials: α- and β-cyclodextrin

Other materials: marine lecithin, α-tocopherol, quercetin, chloroform, methanol, diethylic ether, hexane Wall materials: gelatin, maltodextrin and tannins; emulsifiers: Tween-60; other material: glutaraldehyde Wall materials: gelatin, acacia, and hydrolysable tannins; emulsifiers: hydroxylethyl, cellulose; other material: glutaraldehyde Wall materials: gelatin, acacia, and tannins; emulsifiers: Tween-60; other material: glutaraldehyde Wall materials: chitosan, poly (ethyleneglycolran-propyleneglycol); other material: sodium tripolyphosphate Wall materials: beta-lactoglobulin and low methoxyl pectin

Wall materials: OSA starch, chitosan, and lambda-carrageenan Emulsifiers: Tween-20, Tween-40, Tween-60, and Tween-80 Emulsifiers: Tween-20

Emulsifiers: Tween-80, Span-80, and sodium dodecyl sulfate Emulsifiers: Tween-20

Important raw materials used

Nanoencapsulation techniques

Table 1 Nanoencapsulation techniques of various bioactive compounds

(L)

100 nm

200–580 nm

Capsaicin (L)

BSA (H)

117 and 218 nm 80 nm

Curcumin (L) β-carotene (L)

81 nm

Curcumin (L)

236 nm 27 nm

Curcumin (L)

Linoleic acid (L)

100 nm

300–600 nm

Capsaicin (L)

DHA (L)

100 nm

Capsaicin (L)

121–177 nm

β-Carotene (L) 160–207 nm

132–184 nm

β-Carotene (L)

Salmon oil (L)

130 nm

79–618 nm

Curcumin (L) MCT (L)

40 nm

135 nm

543–1,292 nm

Particle size

Sunflower oil (L)

Flax seed oil (L)

D-Limonene

Bioactive compounds

Belhaj et al. 2010

Yuan et al. 2008a

Yuan et al. 2008b

Preetz et al. 2008

Wang et al. 2008a, b

Leong et al. 2009

Kentish et al. 2008

Jafari et al. 2007b

References

Improving the bioavailability, bioactivity, encapsulation efficiency and enhancing the cellular uptake Improving oral bioavailability and sustainability Improving physical, chemical stability and bioavailability

Improving the solubility

Formation of transparent solution, improve the colloidal stability, protection against degradation and useful for enrichment of acid drinks Improving the thermal stability

Controlling the release of encapsulated protein

Masking its pungent odor and improving the stability

Improving the efficiency and delaying the release property

Ribeiro et al. 2008

Suwannateep et al. 2011

Anand et al. 2010

Gou et al. 2011

Hadaruga et al. 2006

Zimet and Livney 2009

Gan and Wang 2007

Jincheng et al. 2010

Xing et al. 2004

Masking the pungent odor, giving Wang et al. 2008a, b biocompatibility and biodegradation

Increasing the oxidative stability

Protecting the droplets from recoalescence Optimizing operating conditions to prevent the droplet from coalescence and cavitational bubble cloud formation Optimizing the conditions to produce nanoemulsion Enhancing the anti-inflammation activity Improving the stability for use in food or pharmaceutical industry Improving physical stability and commercial application Improving the stability

Purposes

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(L)

β-carotene (L)

Wall materials: modified n-octenyl succinatestarch; other materials: ethyl acetate Wall materials: maltodextrin; emulsifiers: Hi-Cap, whey protein concentrate, and Tween-20

D-Limonene

Catechin (H)

Wall materials: carbohydrate matrix and maltodextrin; other materials: acetone

Spray drying

Curcumin (L)

Wall materials: poly(D,L-lactide-co-glycolide) and polyvinyl alcohol; other materials: chloroform and ethanol

Lutein (L)

9–280 nm

β-carotene (L)

Emulsifiers: Tween-20

Improving the controlled release and encapsulation efficiency Improving the reproducibility, stability and target drug loading yield Optimize the operating conditions and reduce phytosterol loss Minimizing the recoalescence, improve the physical stability and solubility Optimizing the processing condition and improving bioavailability Improving the physical stability

enhance absorption and prolong the rapid clearance of curcumin

For controlled release

Improving the solubility and bioavailability

Purposes

It gives smooth, spherical PLGA nanospheres formation, high yield, drug entrapment efficiency with a narrow size range and sustained delivery 163–219 nm Bioactivity, promote to food industry and to avoid thermal/light degradation 80 nm Increasing the stability, protecting from oxidation and incorporation into beverages 300–600 nm (droplet size); Improving dispersibility, coloring 12 um (particle size) strength and bioavailability 0.2–1.2 μm (emulsion droplet Increasing the retention, stability size); 21–53 μm (dried during process particle size)

115–163 nm

Astaxanthin

Emulsifiers: sodium caseinate

45 nm

90–120 nm

40–260 nm

Coenzyme Q10 (L)

α-Tocopherol (L)

170 nm

Quercetin

50–282 nm

100 nm

Curcumin (L)

Phytosterol (L)

254–415 nm

300–320 nm

Particle size

Curcumin (L)

Astaxanthin (L)

Bioactive compounds

Emulsifiers: Tween-20; other materials: hexane, isopropyl alcohol, ethanol, and acetone Emulsifiers: Tween-20

Wall materials: poly(D,L-lactic acid) and poly(D,L-lactic-coglycolic acid); emulsifiers: gelatin or Tween-20 Wall materials: poly (ethylene oxide)-4methoxycinnamoylphthaloylchitosan, poly(vinylalcohol-co-vinyl-4methoxycinnamate), poly(vinylalcohol), and ethyl cellulose Wall materials: chitosan cross-linked with tripolyphosphate; emulsifiers: Span-80 and Tween-80; other materials: acetic acid and ethanol Wall materials: hydroxyl propyl methyl cellulose and polyvinyl pyrrolidone; emulsifiers: D-α-Tocopheryl polyethylene glycol 1000 succinate, Tween-80, Tween-20, cremophor-RH 40, pluronic-F68, pluronicF127 Wall materials: poly-D,L-lactide and polyvinyl alcohol Wall materials: poly (-methyl methacrylate) and polyvinyl alcohol

Important raw materials used

Supercritical antisolvent Wall materials: hydroxylpropyl methyl precipitation cellulose phthalate

Emulsification–solvent evaporation

Nanoencapsulation techniques

Table 1 (continued)

Jafari et al. 2007a

De Paz et al. 2012

Ferreira et al. 2007

Heyang et al. 2009

Mukerjee and Vishwanatha 2009

Silva et al. 2011

Anarjan et al. 2011

Cheong et al. 2008

Leong et al. 2011

Kwon et al. 2002

Kumari et al. 2010

Dandekar et al. 2010

Sowasod et al. 2008

Tachaprutinun et al. 2009

References

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Vitamin E (L)

Wall materials: polyethylene glycol; emulsifier: Tween-80

Emulsifiers: dioctyl sodium sulfosuccinate, poloxamer Curcuminoids (L) 188, glyceryl monostearate Wall materials: chitosan and sodium tripolyphosphate Catechin (H)

α-Tocopherol (L)

Wall materials: chitosan, zein; emulsifiers: Tween-20

163 and 165 nm

450 nm

164 nm

200–800 nm

Capsicum oleoresin (L) 320–460 nm

Capsicum oleoresin (L) 163–1,984 nm

Wall materials: poly-ε-caprolactone; emulsifiers: pluronic F68; other materials: trehalose, D-sucrose, D-mannitol, dextrose, D-sorbitol gelatin and κ-carrageenan Wall materials: poly-ε-caprolactone; emulsifiers: pluronic F68

200–350 nm

Fish oil (L) Capsicum oleoresin (L) 152 nm

183–714 nm

Fish oil (L)

Wall materials: β- cyclodextrin, polycaprolactone; emulsifiers: pluronic F68; other materials: ethyl acetate Wall materials: poly-ε-caprolactone

Wall materials: poly-ε-caprolactone and gelatin; emulsifiers: pluronic F68

Minimizing the un-encapsulated oil at the surface and maximizing encapsulation efficiency Preventing oxidation and masking the odor

0.21–5.9 μm (droplet size); 25–41 μm (particle size)

Fish oil (L)

Wall materials: maltodextrin; emulsifiers: modified starch (Hi-Cap)/whey protein concentrate

Protecting catechin from degradation

Extending the shelf-life, minimizing environmental stress and can apply to the food products Improving stability and Protecting from environmental factor Increasing the stability, retention percentage and extending the shelf-life Improving the stability

Increasing the oxidative stability and encapsulation efficiency Improving the stability and Rehydrating to study the dispersion characteristics and gel network formation prevents the denaturation Effect of excipients on the stability and particle size of nanocapsules

Purposes

Particle size

Bioactive compounds

Important raw materials used

L lipophilic, H hydrophilic

Freeze drying

Nanoencapsulation techniques

Table 1 (continued)

Dube et al. 2010

Tiyaboonchai et al. 2007

Zhao et al. 2011

Luo et al. 2011

Surassamo et al. 2010

Bejrapha et al. 2011

Nakagawa et al. 2011

Bejrapha et al. 2010

Choi et al. 2010

Jafari et al. 2008

References

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water emulsion (o/w), while water in oil emulsion (w/o) was used to encapsulate water-soluble food active agents such as polyphenols (Zuidam and Shimoni 2010). Nanoemulsions can either be used directly in the liquid state or be dried to powder form using drying techniques such as spray drying and freeze drying after emulsification. Moreover, nanoemulsions possess high kinetic stability due to their extremely small emulsion droplet sizes (Solans et al. 2005; SonnevilleAubrun et al. 2004). The high kinetic stability of nanoemulsions is a real benefit for encapsulation purposes and plays a critical role in the retention of surface oil content of the product (Jafari et al. 2008). Nanoemulsions, being nonequilibrium systems, cannot be formed spontaneously and consequently it needs energy input, generally from mechanical devices or from the chemical potential of the components. Therefore, nanoemulsion formation is generally achieved using high-energy emulsification methods like high shear stirring, high-speed or high-pressure homogenizers, ultrasonicator, and microfluidizer. These methods supply the available energy in the shortest time and possess the most homogeneous flow to produce the smallest droplet sizes (Walstra 1996). The use of nanoemulsion technology for delivering food components and nutraceuticals has been comprehensively reviewed by, Augustin and Hemar (2009), McClements et al. (2009), and Silva et al. (2012). Microfluidisation uses very high pressure (up to 20,000 psi) to force the liquid through the interaction chamber, which consists of microchannels of a special configuration. The emulsion feeds through the microchannels into a collision chamber, leading to formation of fine nanoscale emulsion droplets (Fathi et al. 2012). Jafari et al. (2007a, b, 2008) used microfluidisation, ultrasonication, and silverson (a typical colloid mill with a stator composed of a metal grating in which 2-mm holes are drilled) for emulsification of d-limonene and fish oil and further spray drying to obtain particles. It was reported that microfluidisation was the best emulsification method due to maximum encapsulation efficiency and smaller emulsion droplet size. Jafari et al. (2007a) encapsulated d-limonene using maltodextrin combined with a surface-active biopolymer, i.e., modified starch (Hi-cap), whey protein concentrate (WPC), and Tween 20 as wall materials. Microfluidisation resulted in powder with highest retention (86 %) of d-limonene, smaller emulsion droplets of (700–800 nm), and narrower distribution, which also had good stability during the process. Hi-cap was found to be better than WPC due to less surface oil content and more retention of d-limonene. Moreover, Tween 20 significantly reduced the emulsion droplet size (