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Mincroencapsulation Application of Alternative Food-Preservation Technologies 189 acacia for the production a thermosensitive display material. Firstly proposed in the beginning for the pharmaceutical industry, afterwards microencapsulation, became popular in agriculture, food industry, cosmetic and energy generation [2]. There are many reasons to use encapsulation of active ingredients, the most important ones are: Controlled release of active compounds over the time; Target release of encapsulated materials into human body; Protection of the active substance from the environment; Protection of the encapsulated materials against oxidation or deactivation; Conversion of a liquid into solid; Separation of incompatible components; Masking of odour, taste and activity of encapsulation substance; Gastric irritation reduction; Best handlage of the product. MICROENCAPSULATION: METHODS The choice of the microencapsulation method relies both on the nature and characteristics of the polymeric material used and the properties of the active ingredients. A polymer for microencapsulation should be: Chemistry trifle; Non-toxic; Biocompatible; Autoclavable. Moreover, the polymer can have: Good hiding power; Good adhesion; Good elasticity; Good chemical and physical stability; Resistance to mechanical stress. Table 1 shows the most used polymers for the production of microcapsules, both of natural and of syntetic origin. Table 1: Polymers used NATURAL POLYMERS SYNTETIC POLYMERS Albumin, Alginate, Casein, Chitosan, Cellulose, Gelatin, Gluten, Gum Arabic, K-Carragenen, Kraft Lignin, Methocel, Methylcellulose, Natural Rubber, Pectin, Starch, Sodium Caseinates, Soy Proteins, Whey Protein Ethylene, Polyacrilate, Polyacrilonitrile, Polybutadiene, Polyethylene, Polyisoprene, Polypropylene, Polystyrene, Polyvinyl acetate, Polyvinyl chloride, Silicone Microencapsulation techniques can be divided into two categories: Chemical methods, if the starting materials are monomers or prepolymers and chemical reactions are involved with microsphere formation; Physical methods, if the starting materials are polymers and physical changers usually occur [2].
190 Application of Alternative Food-Preservation Technologies Gallo and Corbo Chemical Methods Emulsion Polymerization In this method a water-insoluble monomer is added dropwise into the aqueous polymerization medium, containing the ingredient to be encapsulated and a emulsifier. Initially, polymer molecules form primary nucleus, thus they growing and entrapping the core material [2]. The size of the particles is ca. 50-500 μm [3]. Interfacial Polymerization In this technology, the polycondensation of two complementary monomers takes place at the interface of two immiscible phases, that are mixed under carefully-controlled conditions to form small droplets of one phase in the other. For this process is it necessary to use a small amount of a suitable stabilizer to prevent droplet coalescence or particle coagulation. Microcapsules can be either monocore or matrix type, depending on the solubility of the polycondensate in the droplet phase [2]. This method was initially applied for the preparation of semipermeable artificial cells and then used for many materials: solids, aqueous solution and organic liquids. The size of microcapsules varies from 2 to 6 µm to 2000 µm [3]. In-situ Polymerization The process involves the direct polymerization of a single monomer shell carried out on a core materials surface. Coating thickness is of 0.2-75 µm and the coating is uniform [4]. Coacervation It is the most promising microencapsulation technology, because the recovery is up to 99%; this method is used mainly to encapsulate flavour oil, fish oil, vitamins and enzymes [5]. This technique is carried out by preparing an aqueous polymer solution (1-10%) containing the core material at 40-50°C; a suitable stabilizer can be added to the mixture to maintain the individuality of the microcapsules. A coacervating agent is gradually added to the solution, thus leading to the formation of partially desolvated polymer molecules, and hence their precipitation on the surface of the core particles. The coacervation mixture is cooled to about 5-20°C, followed by the addition of a crosslinking agent to solidify the microcapsule wall formed around the core particles [2]. The most studied and well understood coacervation system is probably the gelatin/gum acacia system, which presents a major drawback, due to the use of gelatin in foods. However, this issue could be solved by using an enzymatic crosslinking [5]. Liposome Developed in recent years, nowadays this technology is used routinely in food industry and in pharmaceutical area, due to: the high encapsulation efficiency, the simple production method and the good stability of capsules [5]. Liposomes or phospholipide vesicles are structures composed of a lipid vesicle bilayers and are generally large, irregular and unilamellar. Chemically, liposome is an amphoteric compound containing both positive and negative charges [6]. Today, the methods for liposome formation do not use the sonication or organic solvent, and allow the continuous production of microcapsules on a large scale. Several authors have proposed different methods for liposome production for microencapsulation technology [5]. The maximum particle size (16 μm) is obtained by using a liposome concentration of 4 g/l [6].
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Page 4 and 5: CONTENTS Foreward i Preface ii Cont
Page 6 and 7: ii PREFACE Nowadays, western countr
Page 8 and 9: iv CHAPTER 8 Antonio Bevilacqua (1,
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Page 20 and 21: Essential Oils in Foods. Applicatio
Page 22 and 23: Enzymes as Antimicrobials Applicati
Page 26 and 27: Nisin in Foods Application of Alter
Page 28 and 29: Chitosan in foods Application of Al
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Page 38 and 39: Predictive Microbiology Application

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