Microencapsulation 2i1q46

Session 2017-2018 Submitted to:-Dr. Alpa Yadav

Submitted by:- Sadhana Jadon Msc. Food science 3rd sem. 16/MFS/007 1

INTRODUCTION Microencapsulation technology allows a compound to be encapsulated inside a tiny sphere known as microsphere/microcapsule, having an average diameter as small as 1 mm to several hundred micro meters. Many different active materials like drugs, enzymes, vitamins, pesticides, flavors and catalysts have been successfully encapsulated inside microcapsules made from a variety of polymeric and nonpolymeric materials. These microcapsules release their contents at appropriate time by using different release mechanisms. It is a technique by which solid, liquid or gaseous active ingredients are packaged within a second material for the purpose of shielding the active ingredient from the surrounding environment. Thus the active ingredient is designated as the core material whereas the surrounding material forms the shell. Microcapsules may be spherically shaped, with a continuous wall surrounding the core, while others are asymmetrically and variably shaped, with a quantity of smaller droplets of core material embedded throughout the microcapsule. All three states of matter (solids, liquids, and gases) may be microencapsulated. This allows liquid and gas phase materials to be handled more easily as solids. It is one of the effective technique for protecting volatile compounds against evaporation, oxidation and thermal degradation. 2

CLASSIFICATION OF MICROPARTICLE Microcapsule: The active agent forms a core surrounded by inert diffusion barrier. Microsphere: The active agent is dispersed or dissolved in an inert polymer.

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Generally Micro particles consist of two components: • Core material • Coat or wall or shell material

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Microcapsules can be classified into three basic categories as monocored, polycored and matrix types . Monocored microcapsules have a single hollow chamber within the capsule. The polycore microcapsules have a number of different sized chambers within the shell. The matrix type micro particle has the active ingredients integrated within the matrix of the shell material. However, the morphology of the internal structure of a micro particle depends largely on the selected shell materials and the microencapsulation methods that are employed.

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CORE MATERIALS

The core material, defined as the specific material to be coated, can be liquid or solid in nature. The composition of the core material can be varied, as the liquid core can include dispersed and/or dissolved materials. Core materials include flavors, antimicrobial agents, nutraceutical and therapeutic actives, vitamins, minerals, antioxidants, colors, acids, alkalis, buffers, sweeteners, nutrients, enzymes, cross-linking agents, yeasts, chemical leavening agents, and so on. The ability to vary the core material composition provides definite flexibility and utilization of these characteristics often allows effectual design and development of the desired microcapsule properties.

COATING MATERIALS

Many have also been used to describe the material from which capsules are formed: carrier, coating, membrane, shell, or wall. Proteins, polysaccharides and semi synthetic cellulose derivatives are widely used biopolymers used in food emulsions to control their texture, microstructure and stability. The coating material should be capable of forming a film that is cohesive with the core material; be chemically compatible and nonreactive with the core material; and provide the desired coating properties, such as strength, flexibility, impermeability, optical properties, and stability. The

coating materials used in micro encapsulation methods are amenable, to some extent, to in situ modification.

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The typical coating properties such as cohesiveness, permeability, solubility, stability and clarity must be considered in the selection of the proper microcapsule coating material. Coating material properties are:  Stabilization of core material.  Inert toward active ingredients.  Controlled release under specific conditions.  Film-forming, pliable, tasteless, stable.  Non-hygroscopic, no high viscosity, economical.  Soluble in an aqueous media or solvent, or melting.  The coating can be flexible, brittle, hard, thin etc.  Examples of coating materials: Water soluble resins – Gelatin, Gum Arabic, Starch, Polyvinylpyrrolidone, Carboxymethylcellulose, Hydroxyethylcellulose, Methylcellulose, Arabinogalactan, Polyvinyl alcohol, Polyacrylic acid. Water insoluble resins – Ethyl cellulose, Polyethylene, Polymethacrylate, Polyamide (Nylon), Poly (Ethylene Vinyl acetate),Cellulose nitrate, Silicones, Poly lactideco glycolide. Waxes and lipids – Paraffin, Carnauba, Spermaceti, Beeswax, Stearic acid, Stearyl alcohol, Glyceryl stearates. Enteric resins – Shellac, Cellulose acetate phthalate, Zein. 

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PURPOSE OF MICROENCAPSULATION

Microencapsulation of materials is resorted to ensure that the encapsulated material reaches the area of action without getting adversely affected by the environment through which it es. Amongst the principal reasons for encapsulation are: 1. Separation of incompatible components 2. Conversion of liquids to free flowing solids 3. Increased stability (protection of the encapsulated materials against oxidation or deactivation due to reaction in the environment) 4. Masking of odor, taste and activity of encapsulated materials 5. Protection of the immediate environment 6. Controlled release of active compounds (sustained or delayed release) 7. Targeted release of encapsulated materials.

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RELEASE MECHANISM

Different release mechanisms of encapsulated materials provide controlled, sustained or targeted release of core material. Generally there are three different mechanisms by which the core material is released from a microcapsule mechanical rupture of the capsule wall, dissolution or melting of the wall, and diffusion through the wall. Less common release mechanisms include ablation (slow erosion of the shell) and biodegradation. The release mechanism depends on the nature of application. Mechanisms of drug release from microspheres are 1. Degradation controlled monolithic system The drug is dissolved in matrix and is distributed uniformly throughout. The drug is strongly attached to the matrix and is released on degradation of the matrix. The diffusion of the drug is slow as compared with degradation of the matrix. 2. Diffusion controlled monolithic system Here the active agent is released by diffusion prior to or concurrent with the degradation of the polymer matrix. Rate of release also depend upon where the polymer degrades by homogeneous or heterogeneous mechanism. .

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3. Diffusion controlled reservoir system Here the active agent is encapsulated by a rate controlling membrane through which the agent diffuses and the membrane erodes only after its delivery is completed. In this case, drug release is unaffected by the degradation of the matrix. 4. Erosion Erosion of the coat due to pH and enzymatic hydrolysis causes drug release with certain coat material like glyceryl monostearate, beeswax and steryl alcohol etc.

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TECHNIQUES OF MICROENCAPSULATION Physical process  Air Suspension Coating  Spray Drying  Pan Coating Physicochemical Process  Coacervation Chemical Process  Interfacial polymerization  In situ polymerization 11

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Air Suspension method

In the air suspension, the fine solid core materials are suspended by a vertical current of air and sprayed with the polymeric wall material solution. After the evaporation of the solvent, a layer of the encapsulating material is deposited onto the core material. The process can be repeated to achieve the desired film thickness. The size of the core particle of this technique is usually large. The air stream which s the particles also helps to dry them, and the rate of drying is directly proportional to the temperature of the air stream.

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In spray drying the liquid feed is first atomized to droplets and ed with a hot gas which causes the solvent of the droplets to evaporate, leaving dried particles. The particles are subsequently separated from .The drying gas in a cyclone or a bag filter. Spray drying is the most widely used industrial process for particle formation and drying. It is extremely well suited to the continuous production of dry solids as either powder, granulates or agglomerates from liquid feeds.

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PAN COATING

In pan coating, solid particles are mixed with a dry coating material and the temperature is raised so that the coating material melts and encloses the core particles, and then is solidified by cooling; or, the coating material can be gradually applied to core particles tumbling in a vessel rather than being wholly mixed with the core particles from the start of encapsulation.

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 Coacervation There are two methods for coacervation are available, namely simple and complex processes. The mechanism of microcapsule formation is identical, except for the way in which the phase separation is carried out. In simple coacervation: a desolvation agent is added for phase separation whereas complex coacervation involves complexation between two oppositely charged polymers. The three basic steps in complex coacervation are:  Formation of three immiscible phases  Deposition of the liquid polymer coating on the core material  Rigidizing of the coating material  Step-1: The first step of coacervation phase separation involves the formation of three immiscible chemical phases: a liquid vehicle phase, a coating material phase and a core material phase

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The core material is dispersed in a solution of the coating polymer. The coating material phase, an immiscible polymer in a liquid state is formed by  Changing temperature of polymer solution  Addition of salt  Addition of non solvent  Addition of incompatible polymer to the polymer solution.  Inducing polymer Step-2: It involves the deposition of the liquid polymer coating upon the core material. Finally: The prepared microcapsules are stabilized by crosslinking, desolvation or thermal treatment.

(a) Core material dispersion in solution of shell polymer; (b) Separation of

coacervate from solution; (c) Coating of core material by micro droplets of coacervate; (d) Coalescence of coacervate to form continuous shell around core particles

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 Chemical

methods

Interfacial Polymerization (IFP) Interfacial polymerization (IFP) is another chemical method of microencapsulation. This technique is characterized by wall formation via the rapid polymerization of monomers at the surface of the droplets or particles of dispersed core material. A multifunctional monomer is dissolved in the core material, and this solution is dispersed in an aqueous phase. A reactant to the monomer is added to the aqueous phase, and polymerization quickly ensues at the surfaces of the core droplets, forming the capsule walls. IFP can be used to prepare bigger microcapsules, but most commercial IFP processes produce smaller capsules in the 20-30 micron diameter range for herbicides and pesticide uses, or even smaller 3-6 micron diameter range for carbonless paper ink.

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 IN SITU POLYMERIZATION In situ polymerization is a chemical encapsulation technique very similar to interfacial polymerization. The distinguishing characteristic of in situ polymerization is that no reactants are included in the core material. All polymerization occurs in the continuous phase, rather than on both sides of the interface between the continuous phase and the core material, as in IFP. Examples of this method include urea-formaldehyde (UF) and melamine formaldehyde (MF) encapsulation systems.

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General purpose for microencapsulation are to make liquids behave like solids, separate reactive materials, reduce material toxicity, provide environmental protection to compounds, alter surface properties of the materials, control release of materials, reduce volality or flammability of liquids and mask the taste of bitter compounds. Classes of materials relating to food products which has been encapsulated include acids, bases, amino acids, colorants, enzymes, flavors, fats and oils, vitamins and minerals, salts, sweeteners and gases. 

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It facilitates the addition of liquid flavor oils to dry ingredients and provide protection against oxidation and other deteriorative changes. It improves the flow properties. e.g. Thiamine, Riboflavin To enhance the stability. e.g. Vitamins 19

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Encapsulation of enzyme systems responsible for ripening increases the local concentration of both substrate and enzymes in cheese and reduces losses in whey. Also, enzymes are protected from low pH and high ionic strength that exists in cheese. Encapsulated lactic acid and GDL improve flavor and color of streaks made from cured, hot processed pork. Microencapsulated flavor provide the convenience of a solid form over a liquid one with reduced volatility and less oxidation. e.g. citrus oils, mint oils Microencapsulation controls the release of sweetness in chewing gums. To reduce the volatility of materials. e.g. Peppermint oil, methyl salicylate

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CONCLUSION Microencapsulation has been applied in a wide variety of products from different areas, and studies have shown an enormous potential to provide the core with advantageous features, resulting in superior quality products, including in the food industry. However, much effort through research and development is still needed to identify and develop new wall materials and to improve and optimize the existing methods of encapsulation for the better use of microencapsulation and its potential applications.

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THANK YOU

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