1. Know the differences between the various types of Colloidal Dispersions 2.Kno

Question

1. Know the differences between the various types of Colloidal Dispersions 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 4. Understand the basic concepts and the difference(s) between hydrolytic rancidity and oxidative rancidity of lipids 5.Know the class of compounds that are on the market as a result of the recent advances in food lipids 1. Know the differences between the various types of Colloidal Dispersions 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 4. Understand the basic concepts and the difference(s) between hydrolytic rancidity and oxidative rancidity of lipids 5.Know the class of compounds that are on the market as a result of the recent advances in food lipids 1. Know the differences between the various types of Colloidal Dispersions 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 4. Understand the basic concepts and the difference(s) between hydrolytic rancidity and oxidative rancidity of lipids 5.Know the class of compounds that are on the market as a result of the recent advances in food lipids

Explanation / Answer

Ans 1: Colloidal dispersion is defined as the mixed system which consists of a dispersed phase and a dispersion medium i.e., one substance is dispersed as a fine particles in another substance called as dispersion medium. For example solid particles are dispersed in air as dispersion medium in dust. Types of Colloidal dispersions includes foam, solid & liquid aerosol, gels, solid foam, emulsion, sol which is a colloidal suspension and solid sol in the form of solid suspension. The main distinguishing aspect between a true solution and a colloidal solution is the size of the particles i.e., in a true solution like salt and water the sodium chloride molecules are fully dissolved into water and this solution will pass through a membrane without becoming separated while in case of colloidal solution the particles are larger and does not dissolves properly and are dispersed throughout a liquid and they do not pass through a membrane.

      Type of colloidal dispersion

        Dispersed Phase

dispersion medium

Foam

Gas

Liquid

Solid foam

Gas

Solid foam

Liquid Aerosol

Liquid

Gas

Emulsion

Liquid

Liquid

Gel

Liquid

Solid

Solid aerosol

Solid

Gas

Sol

Solid

Liquid

Solid sol

solid

Solid

Ans 2: HLB also known as Hydrophile-Lipophile Balance express the relationship between a hydrophilic i.e., water-loving and a hydrophobic or water-hating groups of a surfactant. The higher the HLB value, the more water soluble the surfactant is. The HLB system dentifyes a surfactant for oil and water emulsification. The HLB System also helps in assigning a number to the ingredient or a combination of ingredients which we want to emulsify. In the HLB system each emulsifier is assigned a numerical value which we call its HLB. All emulsifiers consist of a molecule which combines with both hydrophilic and lipophilic groups. An emulsifier which is lipophilic in character is assigned a low HLB number below 9.0 and one that is hydrophilic has a high HLB number of above 11.0. For the value < 10 : Lipid-soluble (water-insoluble), > 10 : Water-soluble (lipid-insoluble), 1 to 3: anti-foaming agent, 3 to 8: W/O (water in oil) emulsifier, 7 to 9: wetting and spreading agent, 13 to 16: detergent, 8 to 16: O/W (oil in water) emulsifier, 16 to 18- solubilizer.

Ans 3: The main factors that impact emulsion stability includes the type or the quantity of emulsifier, droplet size (smaller the droplet size the stabler the emulsion is), pH (water pH affect the rigidity of the interfacial film as it influencing the ionization of the interfical film constitutents including organic acids and bases, ionizable groups and solids and results in the change in physical properties of the films), viscosity of continuous phase, difference between densities of each phase, addition of stabilizers, temperature (high temperature decrease the emulsion stability as it affect the physical properties of oil, water, films and surfactant solubilities in the oil and water phases), electrostatic charge.

Ans 4:

State: Fats containing saturated fatty acids and are solid at ordinary room temperature. The animal fats belong to this category. While plant fats are unsaturated fatty acids and are liquid at room temperature.

2. Colour, odour and taste: Pure fats are colourless and are of bland taste and they flavour during storage.

3. Solubility: The fats are sparingly soluble in water and are known as hydrophobic but soluble in organic solvents like chloroform, ether, acetone and benzene.

4. Melting point: The melting point of fats depends on the chain length of the fatty acid and their degree of unsaturation. Fats having saturated fatty acids from C4 to C8 are liquid at room temperature and those with C10 or higher are solid and their melting points increase with increasing chain length.

5. Specific gravity: The specific gravity of the fats is less than 1 and they float on water surface. 6. Insulation: The fats possess high insulating power and are bad conductor of heat. A layer of fat below the skin provides a sort of blanket for warm blooded animals.

7. Surface tension: The force with which the surface molecules are held together is called the surface tension. When liquid fat is poured on water it spreads uniformly over the surface of water in the form of a unimolecular layer and thus reduces the surface tension of water.

8.Polymorphisim: Fat exist in different crystalline forms depending on the molecules orient themselves in the solid state. The crystal form of the fat has a prefound effect on the melting point and the performance of the fat in the various applications in which it is utilized. The crystal forms of fats can transform from lower melting to successively higher melting modifications. The rate and extent of transformation are governed by the molecular composition and configuration of the fat, crystallization conditions, and the temperature and duration of storage.

Ans 5: Carbon position in a fatty acid is in the from as COOH- or the carboxy end or from the –CH3 or methyl end. If indicated from the -COOH end, then the C-1, C-2, C-3 etc. If the position is counted from the another –CH3 end then the position is indicated by the -n notation. The positions of the double bonds in a fatty acid chain represented either by using the C-n or the -n notation. So in a 18 carbon fatty acid a double bond between C-12 and C-13 is represented as delta if counted from the –COOH end or as -6 (or omega-6) if counting from the –CH3 end. As the -n notation is used to indicate the positions of the double bonds close to the –CH3 end in fatty acids. And the fatty acids with an odd number of carbon atoms are called odd chain fatty acid while the rest are even-chain fatty acids.

Ans 6: The shelf life of a product has reached, the food undergoes processes which results in rancidity and the shelf life of a product refers to the length of time a product may be stored without becoming unsuitable for use or consumption. These lipids degrade to the point of becoming either unpalatable or unhealthy to ingest. This gives rise to an unpleasant odour and taste in food. Rancidity is the natural process of decomposition of fats or oils by either hydrolysis or oxidation, or both. Hydrolytic rancidity is the hydrolysis of triglyceride into its component fatty acids and glycerol and it results in odor and flavor deterioration is due to individual fatty acids more than the total triglyeride while the oxidative rancidity results from more complex lipid oxidation processes and this affects the oil or fat with some degree of unsaturation. Oxygen combines with unsaturated fatty acids to produce hydroperoxides and free radicals which are very reactive. The resulting products from these reaction cause unpleasant change in the flavor and odor of a food.

      Type of colloidal dispersion

        Dispersed Phase

dispersion medium

Foam

Gas

Liquid

Solid foam

Gas

Solid foam

Liquid Aerosol

Liquid

Gas

Emulsion

Liquid

Liquid

Gel

Liquid

Solid

Solid aerosol

Solid

Gas

Sol

Solid

Liquid

Solid sol

solid

Solid

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