Food Dispersion: Colloids and Emulsions Explained

[00:00:02][Laughter] [Music] hello guys welcome back to another video of food for knowledge today we will be discussing the first unit from principle of Food Science called as food dispersion and if you haven't watched our previous video please watch it link is in the description so without further Ado let's get into the video starting with an introduction let us first talk about solution and colloidal systems a solution is a homogeneous mixture of two or more different substances for example salt and water form a solution a colloidal system on the other hand is a heterogeneous system the material that forms the base of the system is called as the dispersion medium or the continuous phase the material that exists in the colloidal condition is called as dispersed medium or discontinuous phase all the three states of matter gaseous solid and liquid may be obtained in different colloidal condition let us know more about colloids and colloidal system by learning about their classification colloidal solution depending upon the nature of interaction between dispersed phase and dispersion medium are classified into lyophilic colloids the colloidal solution in which the particle of the dispersed phase have a great affinity for dispersion medium are called as lyophilic colloids in such colloids the dispersed phase does not participate easily and colloids are quite stable lyophilic colloids the colloidal solution in which the particle of the dispersed phase have great affinity for dispersion medium are called as lyophilicoloids in such Collis dispersed phase does not precipitate easily and the colloids are quite stable if the dispersion medium is separated from the dispersed phase the colloid can be reconstituted by simply mixing with the dispersed medium hence this colloids are reversible in nature example colloids of gum polymers in organic solvent lyophobic lies the colloidal solution in which there is no Affinity between the particle of the dispersed phase and dispersion medium are called as lyophobic colloids these colloids are easily precipitated on additional small amount of electrolytes by hitting or by shaking and therefore are not stable once precipitated it is not easy to reconstitute the colloid by simple mixing with the dispersion medium hence this collides are irreversible in nature example colloids of metal colloidal system can also be classified based on the nature of dispersed phased and continuous phase moving on to soles and gels souls and gels are usually reversible colloidal dispersion of protein or complex carbohydrate soul is a fluid whereas gel is semi-solid colloidal system a colloidal system in which solid particles are dispersed in liquid phase termed as soles example gelatin mixed in water and starch suspension skim milk is also a soul because the milk protein is dispersed in water being colloidal salts exhibits some characteristic properties souls are liquids which are purable at room temperature they have an opaque or clear appearance since they do not exhibit rigidity or form they are free-flowing the dispersed particle in a soul scatter and polarized light colloidal particle in a soul also exhibit rapid irregular movement Soul particles have similar charge on their surface say so they do not coalesce and they repel each other next up we have forms forms make a vital contribution to the volume and texture of many common food products they give volume and distinctive mouth feel to product such as whipped cream and ice cream they give a light Airy texture to pay baked goods a form contained gas bubble dispersed in liquid continuous phase the liquid phase may be a simple dispersion as in egg white which is dilute protein dispersion or it may be a complex containing emulsified fat droplets Ice Crystal or solid metal example of complex food forms include ice cream angel food cake marshmallow forms such as meringue and baked goods are heat sensitive which denatured protein and converts the liquid phase to a solid phase this gives permanence to the form structure they have following characteristics food forms are opaque in appearance they contain large amount of entrapped gas as bubbles they have large surface area between the dispersed gaseous space and continuous liquid phase walls of Foams are rigid and elastic and they reflect light depending on the size of gas bubble and the thickening of the wall liquid walls forms are categorized as light or dense forming agents the two most important characteristics of a foam are foam volume and form stability foam volume depends on the ability of the foaming agent to absorb at the interface and rapidly reduce interfacial tension and on the level of energy input during whipping form stability depends on the ability of the foaming agent to produce a stable interfacial film and a viscous continuous phase although all the surfactants are able to reduce surface tension and produce forms not not all are able to form stable forms a good forming agent has the same characteristic as an mlc file and that is they are able to absorb at the interface reduce interfacial tension and form a stable interfacial film that resists rupture as might be as expected the best forming agent used in foods are protein although many proteins are able to produce forms egg white protein are superior forming agents and are used in food forms such as mangoes angel cake and other baked Cuts other proteins used as good forming agent includes gelatin and milk protein immersions and Emulsion is a colloidal system containing droplet of one liquid dispersed in another the two liquid being immiscible the droplets are termed the dispersed phase and the liquid that contains dam is termed The Continuous phase in food Emulsion the two liquids are oil and water if water is the continuous phase the immersion is said to be oil in water whereas if oil is the continuous phase immersion is termed as water in oil oil and water immersions are more common and in mayonnaise cake batter and frozen dessert butter and some icing are also example of water in oil an Emulsion must also contain an emulsifier which coats the immersion droplets and prevent them from coalescing or recombining with each other to reduce the surface or interfacial tension something must be done to decrease the attractive force between the liquid molecules so that it is easier to spread them this can be achieved by adding surface active molecules or a surfactant a section of the molecule is water loving or hydrophilic because it is polarized or charged and a section is water heating or hydrophobic because it is a non polarized in other words the molecules are amphiphilic example polar lipids such as lecithin which has a polar head and a non-polar tail or surfactant and may be used as food additives to increase the vertibility and a in mixing of products like hot chocolate mix proteins are surface active because they contain both hydrophilic and hydrophobic section some spices such as dry mustard and paprika are also used as surface active ingredients this finely divided powder tends to gather at the surface rather than the bulk of the liquid so now you must be thinking how an immersion is formed an immersion is formed when oil water and an emulsifier are mixed together although there are different food immersion they all contain these three components to form an immersion it is necessary to break up either the oil or the water phase into small droplets that remain dispersed throughout the other liquid this requires energy and is usually carried out using a mixture or a homogenizer as the oil and water I'll mix droplets are formed and immersifier is absorbed at the surface of new droplets decreasing the interfacial tension and allowing formation of some smaller and more droplets there are four types of immersion which are important or potentially so in foods first is the oil in water immersion droplets of oil are suspended in an aqueous continuous phase these are the most versatile of immersion types they exist in many forms like mayonnaise cream Liquors creamer whippable topping ice cream mixes and Etc and their property can be controlled by varying both the surfactant using and the component present in the aqueous phase second type we have water in oil immersion are typeified by butter and fat based spreads in general this depend for their stability more on properties of fat or oil and the surfactant used than in the properties of aqueous phase and because of this there are fewer parameters which can be varied to control their stability the third of the immersion type is water in oil in in water which is in effect immersion whose droplets themselves contain water droplets these are the most difficult immersion to produce and control because the water droplet is contained in the oil drop list must be stable as must the oil droplet contain in continuous Aqua space the fourth type of Emulsion is oil in water in oil immersion which is a double immersion system in which the dispersed phase is an oil in water immersion and the continuous phase is oil or plastic fat because of its limited application and food product comparatively limited work has been done on the oil in water in oil emulsions MIT fires emulsifiers must be able to absorb at the interface between two liquids such as oil and water reduce the interfacial tension of each liquid enabling one liquid to spread more easily around the other form a stable coherent viscoelastic interfacial film prevent or delay coalescence of the immersion droplets reduce the interfacial tension facilitates immersion formation because it reduces the amount of energy needed to break up one liquid into droplets and to spread the other drop liquid around them formation of film that prevents coalescence promote immersion stability characteristics or function of an emulsifiers contain hydrophilic and hydrophobic section amphiphilic absorbed at the oil or water interface reduce the interfacial tension forms a stable interfacial film prevents coalescence natural emulsifiers the best emulsifiers are protein which uncoil or denature and absorbed at the and interact to form a stable interfacial film protein tends to uncoil such that their hydrophobic section are oriented in oil and their hydrophilic sections are oriented in water hence a series of loop trains and tails may be envisioned at the interface example the protein of egg yolk tend to be the best emulsifiers as exemplified by the used in mayonnaise this protein are lipoprotein and are associated with each other and with phospholipids such as lecithin and structure known as misses the missile structure appears to be responsible for the excellent emulsifying properties of agioprotein the casein of milk are also excellent emulsifying agent they are important emulsifiers in homogenized milk and in Dairy desert in fresh milk the cashew are associated with each other in structures known as Cuisine Mrs electron micrographs have shown that after homogenization intact missiles are present at the fat globule surface as well as individual protein molecule it is thought that missiles are responsible for the stability of homogeneous milk rather than individual protein molecule synthetic emulsifier or surfactants more synthetic emulsifier would more correctly be termed surfactant because they are relatively small molecules compared with protein and they are used mainly to Aid in dispersion of fat rather than to stabilize immersion glycerol monosterate is an example of monoglyceride that is commonly used in food acid may be as certified with monoglyceride to give another group of surfactant including sodium steroid 2 electrolate which is often used in baked products scenariosis also known as whipping is water freed from a cooked cold starch gel the process is a change following gelatinization and is caused by gelation as a cooked cold star gel stands the gel ages then further Association of amylose occur and the gel contracts causing both water loss and shrinkage to become apparent this is caused by retrogradation and is the separation of a liquid from a gel upon standing the process is a change of following gelatinization and caused by gelation if cold and Disturbed the jail remains strong get reassociation may be accompanied by the unacceptable water loss to control scenariosis modified starch or starches containing only non-gelling amylopectin are used in commercial product research has well established that the cooling condition will impact the strength of the gel generally if cooled too fast the amylose will not have time to form the vital misses necessary for the 3D structure if cooled too slowly the minus fraction will have a chance to align too much and become too close together and the liquid portion will not be trapped in missiles in both instant there will be whipping and scenariosis so with this we are done with today's topic and if you enjoyed our video please hit the like button and 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