EDIBLE COATINGS AND FILMS TO IMPROVE FOOD QUALITYMs. Latika Yadav (Research Scholar), Dept. of Foods and Nutrition, College of H.Sc,Maharana PratapUniversity of Agriculture and Technology, MPUAT, Udaipur, rajasthan-313001, email.id: email@example.com
OUTLINE1. Introduction2. History of edible films and coatings3. Use of edible films and coatings4. Components of edible coatings5. Role of edible films and coatings6. Commercial edible coating and films7. Application of commercial coating8. Method of coating application9. Encapsulation of flavours , nutraceuticals and antibacterials10. Comparison of typical food coatings and pharmaceutical coatings11. Evaluation of edible films
INTRODUCTIONAny type of material used for enrobing (i.e.. coating orwrapping) various food to extend shelf life of the productthat may be eaten together with food with or withoutfurther removal is considered an edible film or coating.Edible films provide replacement and/or fortification ofnatural layers to prevent moisture losses, whileselectively allowing for controlled exchange of importantgases, such as oxygen, carbon dioxide, and ethylene,which are involved in respiration processes.A film or coating can also provide surface sterility andprevent loss of other important components. Generally,its thickness is less than 0.3 mm.
HISTORY OF EDIBLE FILMS AND COATINGSEdible coatings have been used forcenturies to protect foods and preventmoisture loss.The first recorded use was in china in the12th century on citrus, and later inEngland using lard or fats, called lardingto prolong shelf life of meat products.Since the early to mid 20th century,coatings have been used to prevent waterloss and add shine to fruits andvegetables, as casings using collagen orcollagen-like material for sausages, andas some sort of sugary coatings onconfectionaries, including chocolate.
Use of Edible Films and Coatings1. Reduce water loss2. Reduce gas diffusion3. Reduce movement of oils and fats4. Reduce movement of solutes5. Reduce loss of volatile flavors & aromas6. Improve structural properties (hold it together)7. Incorporate pigments, flavoring, & food additives8. Improve appearance (e.g., gloss)9. Inhibit transfer of moisture and oxygen10. Reduced mold growth11. Reducing frying fat uptake12. Reduce adhesion to cooking surface.
COMPONENTS OF EDIBLE COATINGS Polymers are the main ingredients of many edible coatings. Many edible polymers are nontoxic, simple derivatives of cellulose, one of the most abundant natural polymers in nature, being a component of plant structure. The coatings made from polymeric edible films are generally designed to be flexible and tough. Components of edible coatingpolysaccharides proteins lipids resins composite
1. POLYSACCHARIDES: coatings are hydrophilic and intermediate among coatings materials in gas exchange properties but are poor barriers to moisture. These include cellulose derivatives, starch derivatives, chitosan, pectin, carrageenans, alginates and gums. Polysaccharides films/ coatings Microbial Seaweeds extract starch Chitin/chitosan cellulose polysaccharides levan carrageenan dextrins CMC pullulan alginates amylose HPC MC
2. PROTEINS: are similar in properties, being also hydrophilic, and include cornzein, wheat gluten, peanut, soy, collagen, gelatin, egg, whey and casein. Protein films/ coatings gelatin zein Wheat gluten casein Whey protein Albumen + gelatin Soy protein
3. LIPIDS: lipds and waxes tend to be more permeable to gasses but present abetter barrier to water vapour and includes beeswax ,petroleum based waxes,vegetable oils etc. Lipid films /coatings surfuctants waxes tweens lecithin beeswax carnauba paraffin
Properties of Hydrocolloids Properties of Lipid Coatings •Poor resistance to water vapor •Barriers to oxygen & carbon dioxide •Barriers to water vapor •Mechanical strength •Coatings add gloss •Water soluble (i.e., hydrophilic) •Lack structural strength & durability •Water insoluble (i.e., hydrophobic) •Require supporting matrix •Many lipids exist in crystalline form 4. RESINS: resins are the least permeable to gases and intermediate in resistance to water vapor and include shellac, wood rosin, and coumarone indene resin.female lac bug shellac Wood rosin coumarone indene
5. Composite films: Blend of polysaccharides, proteins, lipids or resins. Structure of Composites
Properties of Composites•Combine advantages of components•Lessen disadvantages of components•Example–Lipids provide a barrier to water vapor movement–Hydrocolloids provide the supporting matrix•Example–Films of casein and acetylated monoglycerides are effective barriers to water loss infruits and vegetables Film Additives •Modify mechanical properties of the film •Cause significant changes in barrier properties
Types of Film Additives •Emulsifiers keep the components in solution.Components of Film Additives •Surfactants reduce the surface tension of the•Antimicrobial compounds film formulation to achieve uniform coverage.•Antioxidants Surfactants may be used to stabilize the•Flavor and aroma compounds dispersed phase in a polymeric solution prior to•Pigments applying it to food surface.•Preservatives•Vitamins •Plasticizers: Plasticizers are used to modify mechanical properties of films and coatings Plasticizers, which are small molecules such as glycerol, propylene glycol, or polyethylene glycol are used to control viscosity of the liquid formulation, add flexibility and tensile strength and control surface tension.
ROLE OF EDIBLE FILMS AND COATINGS1. Antimicrobial agents: incorporating antimicrobial compounds into edible films orcoatings provides a novel way to improve the food safety and shelf life of ready-to-eatfoods.Common antimicrobial agents used in food systems, such as benzoic acid, sodiumbenzoate, sorbic acid , pottassium sorbate, and propionic acid, may be incorporated intoedible films and coatings. Example:•Starch based coating containing potassium sorbate wereapplied on the surface of fresh strawberries for reducingmcrobial growth and extending storage life.•Chitosan coatings containing potassium sorbate wereshown to increase antifungal activity against the growth ofCladosporium and Rhizopus on fresh strawberries.
2. Antioxidants and antibrowning agents:Antioxidants can be added into coating matrix to protect against oxidative rancidity,degradation and discoloration of certain foods. E.g. nuts were coated withpectinate, pectate, and zein coatings containing BHA, BHT, and citric acid toprevent rancidity and maintain their texture.Ascorbic acid was incorporated into edible coatings to reduce enzymatic browningin sliced apples and potatoes.3.Nutrients, flavours and colorants:Edible films and coatings are excellent vehicles to enhance the nutritional valueof fruits and vegetables by delivering basic nutrients and nutraceuticals that arelacking or are present on only low quantity.Xanthan gum coating was utilized to carry a high concentration of calcium andvitamin E, for not only preventing moisture loss and surface whitening, but also tosignificantly increase the calcium and vitamin E contents of the carrots.
Classification of some antimicrobial, antioxidant agents and additives allowed for used in food coatings Food additive classification Allowed useBenzoic acid Preservative GRASClove bud oil Essential oil GRASPotassium sorbate Preservative GRAS/FSPropionic acid Preservative GRAS/FSCalcium chloride Antimicrobial agent GRAS/FSAscorbic acid Antioxidant, preservative, GRAS colour stabilizer, nutrientButylated hydroxyanisole Antioxidant GRAS/FS(BHA)Butylated hydroxytoluene Antioxidant GRAS/ FS(BHT)
Edible coatings have been successfully applied in processed foods such as meat,cereals, confectionaries, dried fruits, nuts and fresh and fresh-cut fruits andvegetables.These coating improves the quality and shelf life of foods.These films acts as a novel packaging systems and control the release of activecompounds such as antioxidants, flavours, and antimicrobial agents. 1. Meat films and coatings 2. Cereal coatings 3. Raisin and Nut coatings 4. Confectionary coatings 5. Strips and pouches
Some commercial edible coating and films Commercial composition uses Web site namenatureseal® Ascorbic acid, Browning www.natureseal.com calcium chloride, inhibition, hydroxypropyl maintain taste, methylcellulose texture and colour of fresh-cut fruits and vegetablesSemperfresh TM Sucrose esters of Coating of whole www.paceint.com short-chain pears and cherries unsaturated fatty to control weight acid and sodium loss and excess salts of respiration, retain carboxymethyl moisture, and cellulose preserve natural colour of fruitPro-long TM Sucrose Coating for fresh www.matrose.com polyesters of fruits and fatty acids and vegetables sodium salts of carboxy-methyl cellulose
Mantrocel ® hydroxypropyl Film coating for tablets www.matrose.com methylcellulose and capsules, binder, filler, matrix, stablizercrystalac ® Shellac Confectionary glaze www.matrose.comCrystalac ® Zein Confectionary glaze www.matrose.comZ2Flavoured film Films made Breath freshners, oral www.watson-strips from hygiene, sugar free inc.com hydrocolloids, candy, caffeine/energy, plasticizers, and vitamin/nutrient active strips compounds, flavours and colorantsOrigami ® Fruit and Wrapping, pouches, www.origamifoods.cwraps vegetable- based sachets om films with bilayer protein films
APPLICATION OF COMMERCIAL COATINGEDIBLE COATINGS can be utilized for most foods to meet challenges associatedwith stable quality, market safety, nutritional value, and economic productioncost. The potential benefits of using edible coatings on fresh and processed foodproducts are:1. Coating can serve as a moisture barrier on the surface of fresh and minimally processed produce for helping to alleviate the problem of moisture loss during post harvest storage, which leads to weight loss and changes in texture, flavour and appearance.2. Coating also function as a gas barrier for controlling gas exchange between the fresh produce and its surrounding atmosphere, and thereby decrease respiration and delay deterioration, retard enzymatic oxidation, and protect against from browning discoloration and loss of texture during storage.
3. Coating protect produce from physical damage caused by mechanical impact, pressure, vibrations and other factors.4.Coating functions as a carriers of active ingredients, such as antimicrobials, antioxidants, nutraceuticals, colors, flavours and other additives used to improve quality.Successful application of edible coatings on food is dominated by several factors:• type of coating material• Its specific formulation• The method of application• The surface characteristics of the food
METHOD OF COATING APPLICATIONSeveral coating application methods including:1. Dipping2. Dripping3. Foaming4. Fluidized-bed coating5. Panning6. Spraying7. Electrostatic coatingThe selection of an appropriate method depends on the characteristics of the food, the coating materials, the intended effect of the coating, and the cost.
1. Dipping: edible coatings can be applied by dipping productsin coating solutions and then allowing excess coating to drain asit dries and solidifies.Dipping has been commonly used for coating fruits, vegetables,and meat products.The first reported dipping application was by the Florida citrusindustry, where the fruits were submerged into a tank of emulsioncoating. Fruit was then generally conveyed to a drier underambient condition2. Dripping: This coating application method isthe most economic. In addition, it has the ability todeliver the coating either directly to thecommodity surface or to the brushes. However,due to relatively large droplet sizes, good uniformcoverage can only be achieved when thecommodity has adequate tumbling action overseveral brushes that are saturated with thecoatings.Dripping has been commonly used for coatingfruits and vegetables
3. FOAMING: foam application is used for some emulsion coatings. A foaming agent isadded to the coating or compressed air is blown into the applicator tank. Extensivetumbling action is necessary to break the foam for uniform distribution. The aggitated foamis applied to commodities moving by on rollers and cloth flaps or brushes the distribute theemulsion over the surface of the commodity.This type of emulsion contains little water and therefore dries quickly, but inadequatecoverage is often a problem.
4. FLUIDIZED-BED COATING: is a technique that can be used to apply a very thinlayer onto dry particles of very low density or small size. It was originally developed as apharmaceutical coating techniques but is now increasingly being applied in the foodindustryIt may be applied to enhance the effect of functional ingredients and additives such asprocessing aids, preservatives, fortifiers,flavours and other additives for ease of handling,improved asthetics, taste and colour.Bakery products are commonly coated using fluidized-bed techniques.
5. PANNING: panning is usually employed for coating candies ,nuts, and someprocessed fruits that are characterized by a smooth, regular surface obtained by polishingaction in the pan. The technology involves a stainless steel pan that is enclosed andperforated along the side panels. The coating is delivered by a pump to spray gunsmounted in various parts of the pan.Panning is a slow process, in which the pan speeds vary based on the size of the centre.For ex- large size nuts require speeds of 15rpm.
6. SPRAYING: when a thin and uniform coating is required for certain surfaces,spraying is useful. This the most popular method for coating whole fruits andvegetables, especially with the development of high-pressure spray applicators andair- atomizing systems. Spray applications are also suitable when applying films to aparticular side or when a dual application must be used for cross-linking, as ispractised with alginate coating.
7. ELECTROSTATIC COATING: is a process that employs charged particles to improve efficiently coat a surface. Powdered particle or atomized liquid is initially projected towards a conductive surface using formal spraying methods and then accelerated toward the surface by a powerful electrostatic charge. The exact performance of liquid electrostatic coating systems for food applications is not well known. These coating shown great promise in some applications, including the impregnation of bread with edible vegetable oil and coating of confectionary and chocolate products.The success of an edible coating for meeting the specific needs of foodstrongly depends on•Its barrier property to gases, especially oxygen and water vapour•Its adhesion to the surface•Uniformity of coverage of coating and also•Sensory quality of the coated food products
Encapsulation of flavours , nutraceuticals and antibacterialsEncapsulation is the technique by which one material or mixture of materials is coatedwith or entrapped within another material or system. The coated material is called theactive or core material, and the coating material is called the shell, wall material, carrier,matrix, or encapsulant.Encapsulation technology is now well developed and accepted within thepharmaceutical, chemical, cosmetic, food, and printing industries.In food products, fats and oils, aroma compounds and oleoresins, vitamins, minerals,colorants, and enzymes have been encapsulated, while in films of coating oils, aromacompounds, antimicrobials, and enzymes have been encapsulated.
Encapsulation methods are broadly categorized as either physical or chemical Physical Methods1. Extrusion2. Fluidized bed3. Pan coating4. Atomization Chemical Methods5. Spinning disk6. Spray drying 1. Solvent loss7. Spray chilling/congealing 2. Phase separation 3. Coacervation 4. Polymerization 5. Precipitation 6. Nanoencapsulation 7. Liposomes 8. Sol-gel
CAPSULES MATRICES: encapsulation of biomolecules can be achieved by using two main methods:1. The first consist in making capsules in which the compound included as a core entrapped in a polymeric matrix.2. The second method consists of developing films or coatings in which the biomolecules are directly included and trapped just as a matrix but on a larger scale.
Release Mechanisms capsule formulations to achieve one or more release mechanisms to meet product performance requirements. Common Controlled Release Profiles 1. Triggered release – Release occurs due to a change in environment, such as pH, temperature, moisture, pressure, electromagnetic. This is used to achieve immediate, delayed or pulsatile release profiles. 2. Sustained release – Release occurs for an extended period of time. This can be used to achieve constant active ingredient exposure for a fixed period. 3. Burst release 4. Combination release profilesRelease Mechanisms1. Diffusion2. Dissolution3. Molecular trigger (such as pH)4. Biodegradation5. Thermal Osmotic release is triggered by the absorption of6. Mechanical water into the microcapsule core. Subsequent7. Osmotic swelling ruptures the microcapsule shell.
Encapsulation of nutraceuticals•Several nutraceuticals molecules can be incarporated inedible coatings such as vitamins, peptides, polyunsatturatedfatty acids, or antioxidants to increase the food nutritionalvalue.•The main problem in incorporating nutraceuticals in food isrelated to stability during storage . These reactive moleculesrapidly lose their activity due to oxidation or other chemicalreactions.•Edible films and coatings used to protect these activebiomolecules from contact with foods. While incorporated incoatings or encapsulated, there bioactive effect is preserved,and nanoencapsulation increases the molecule’sbioavailability.•Milk proteins, maltodextrins and other modified starches arelargely used as encapsulation matrices .
Edible materials for nutraceuticals or antimicrobial molecule encapsulationThe matrix used for nutraceuticals or antimicrobial molecules is of prime importance to allow good preservation or controlled release of these active compounds1. HPMC( hydroxypropyl methylcellulose):• cellulose based materials are being widely used as they offer advantages like edibility, biocompatability, barrier properties, and asthetic appearance as well as being nontoxic, nonpolluting and having low cost.• HPMC edible films are attractive for food applications because HPMC is a readily available nonionic edible plant derivative shown to form transparent, odorless, tasteless, oil-resistant, water- soluble films with very efficient oygen, CO2, aroma and lipid barriers, but with moderate resistance to water vapour transport.• The tensile strength of HPMC films is high, and flexibility is neither too high nor too fragile, which make them suitable for edible coating purposes.
2. PLA ( Polyacetic acid):As a GRAS and biodegradable material, and also because of its biosorbability andbiocompatible properties in the human body, PLA and its copolymers( especially polyglycolic acid) attracted the pharmaceutical and medical researchers.PLA is a new corn-derived polymer and needs time to be an accepted and effectiveactive packaging material in the market. PLA ( Polyacetic acid)
COMPARISON OF TYPICAL FOOD COATINGS AND PHARMACEUTICAL COATINGS Food coatings Pharmaceuticals coatingsAmount used Thickness of a fruit coating is Tablet film coatings are much thicker, often 2μm, and this makes up 0.02% of about 50 μm. Sugar coatings make up about fruit weight 40% of pill weight.complexity Typically one uniform layer Multiple layers are commonWhat is inside Usually food inside and air Before ingestion: active ingredient insideand outside outside and air outsidethe coating After ingestion: active ingredients inside stomach and outside intestines.Main Reduce gas ( oxygen or water Before ingestion: mask and impart color,functions vapour) movement into or out of reduce gas movement into the active the food ingredient. After ingestion: mask and impart flavour, reduce gas movement, control release rate of active ingredient.
Food coatings Pharmaceuticals coatingsImportant modeling Permeance of gas diffusion through Before ingestion: same as for foodparameters coatings, coating thickness, and gas coatings, plus diffusion of active effusion through holes in the coating ingredients within the tablet. After ingestion: diffusion of active ingredient through wetted coating, including leaking through holes in the coating, possible driven by osmotic flow.Coating technology Processing to apply coatings must be Freedom to use extensive cheap, gentle, and fast to avoid handling, higher temperatures, product damage. Slow development more ingredients, and higher-cost of new technology techniques have led to ever more sophisticated and highly engineered coatings.Permitted GRAS food additives plus relatively Wide range of ingredients,ingredients few other ingredients including many synthetic polymers
EVALUATION OF EDIBLE FILMS1. BARRIER PROPERTIES• Water vapour permeability (WVP): the rate of water vapour transmission per unit area of flat material of unit thickness induced and per unit vapour pressure difference between two specific surfaces, under specified temperature and humidity conditions.• Gas permeability :The permeability of oxygen gas through a material is a critical factor when it concerns the ability of a package to prolong the lifetime of packaged food. Gas permeability of two types:• Oxygen permeability test• Carbon-di-oxide permeability test
2 . MECHANICAL PROPERTIES1. Tensile strength (TS): The tensile strength ofa material quantifies how much stress the materialwill endure before suffering permanentdeformation. This is very important in applicationsthat rely upon a polymers physical strength ordurability.2. Elongation (EL): The increase in asamples gauge length measured after arupture or break divided by the samplesoriginal gauge length is referred to aselongation. The greater the elongation, thehigher the ductility or elasticity of thematerial.
3. Puncture test: This test method determines theresistance of a stretch wrap film to the penetration ofa probe at a standard low rate, a single test velocity.Performed at standard conditions, the test methodimparts a biaxial stress that is representative of thetype of stress encountered in many product end-useapplications. The maximum force, force at break,penetration distance, and energy to break aredetermined .4. Texture analyzer: Texture analysis isprimarily concerned with measurement of themechanical properties of a product such ashardness, softness, cohesiveness, guminess etc.
3. American Society for Testing and Materials (ASTM) : ASTM International, formerlyknown as the American Society for Testing and Materials (ASTM), is a globallyrecognized leader in the development and delivery of international voluntary consensusstandards. Today, some 12,000 ASTM standards are used around the world to improveproduct quality, enhance safety, facilitate market access and trade, and build consumerconfidence .
References1. Elizabeth A. Baldwin.et.al; 2012,“ edible coatings and films to improve food quality, second edition, CRC Press.2. http://wenku.baidu.com3. http://www.astm.org4. http://www.foodsafetymagazine.com5. http://www.inviz.com6. http://www.wikipedia.com7. http://www.google.com