Know the differences between the various types of Colloidal Dispersions 1. 2. Kn
ID: 544069 • Letter: K
Question
Know the differences between the various types of Colloidal Dispersions 1. 2. Know the basic concept of HLB and how it is used to describe emulsifiers 3. Know the 3 main factors that impact emulsion stability 4 Know the physical properties of food fats/oils including melting point and polymorphism 5. Fatty Acid Nomenclature Be able to describe a Fatty Acid given the nomenclature Understand the basic concepts and the difference(s) between hydrolytic rancidity and oxidative rancidity of lipids 4. 5. Know the class of compounds that are on the market as a result of the recent advances in food lipidsExplanation / Answer
1. The difference between various types of colloidal dispersions depends on the dispersed phase and the dispersion medium. Lets know the diffeences:
a. Foam - in which the gas(dispersed phase) is dispersed in a liquid medium(dispersion medium)
b. Solid Foam - in which the gas is dispersed in a solid medium
c.Liquid Aerosol - in which the liquid is dispersed in a gaseous medium.
d. Emulsion - in which the liquid is dispersed in a liquid medium.
e.Gel - in which the liuid is dispesed in the solid medium
f.Solid Aerosol - in which the solid particles are dispersed in a gaseous medium.
g.Sol / Colloidal Suspension - in which the solid particles are dispersed in a liquid medium
h. Solid Sol - in which the solid particles are dispersed in a solid medium.
2. The Hydrophilic- Lypophilic balance of the surfactant is the measure of te degree to which it is hydrophobic or lyophilic . In other words it is an emperical expression fo the relation ship between water loving and water hating group ofsrfactants. HLB values renge from 0-20. Value of 0 denotes it is completely hydrophobic. Value of 20 depicts it is completely hydrophilic.
HLB values ae used to determine the surfactant properties of a molecule.
3. Temperature, doplet size of the emulsion and pH are the three main factors whch affect the stability of emulsions.
4. The physical properties of fats and oils are :
a. An increase in the percentage of shorter-chain fatty acids and/or unsaturated fatty acids lowers the melting point of a fat or oil.
b. They are insoluble in water but soluble in organic solvents.
c. They have lower specific gravity than water and consequently will float on surface whenmixed with it.
d. They readily form emulsions when agitated with water in the presence of soap, gelatin or other emulsifiers.
Polymorphism: The melting point of a fat or oil depends on its structure. If all the fatty acids forming a triglyceride ae saturated, their carbon chains can align themselves in a regular pattern. Such molecules can pack well in a crystal, and thus form solids at room temperature. Onthe other hand, if some of the este chains are formed by unsaturated acids, there are kinks in their carbon chains at the double bonds that have cis configuration. These kinks make the carbon chain iregular and do not allow close packing of the molecules. Thus in general , oils contain glycerides in which unsaturated acids preponderate. On the other hand in solid fats saturated acids preponderate.
5. Fatty acid nomenclature:
The nomenclature of fatty acids is confusing with many different names being used for the identical substance.
A fatty acid is unsaturated if there is at least one double bond between the carbon atoms in the fatty acid. A fatty acid with only one double bond is called a monounsaturated fatty acid. A fatty acid with two or more double bonds is called a polyunsaturated fatty acid. A fatty acid with no double bonds between the carbon atoms in the main carbon chain of the fatty acid is called saturated fatty acid.
The term “omega” refers to the position of double bond in relation to methyl group on the end of the fatty acid.
As an example, omega-3 (-3) fatty acids have the last double bond 3 carbons from the terminal methyl group.
The term “n” can be used in an identical fashion.
Hence, omega-3 fatty acid, -3 fatty acid, and n-3 fatty acid are all different ways of writing the identical fatty acid.
4. In hydrolytic rancidification, the ester linkages of a glyceride are hydrolysed to give the original fatty acid. For example, when butter is left uncovered and out of refrigerator, it goes rancid. The butter-fat is hydrolysed by microorganisms in ai, producing butyric acid which has a unpleasant odor.
In oxidative rancidification, atmospheric oxygenattacks the carbon-carbon double bonds in the unsaturated side chains of glyceride. Thus short chain volatile carboxylic acids and aldehydes are formed. These have extremely bad odors.
5. Lipids are a diverse class of compounds that contribute to the organoleptic, physicochemical and nutritional aspects of foods and food ingedients. omega fatty acids , n-3 polyunsaturated fatty acids and several other are the food lipids which have made impact in the markets.
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