Ppt0000003 - Know 2 methods to analyze total protein...

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Unformatted text preview: Know 2 methods to analyze total protein content in foods- Kjeldahl & Dumas  Understand the chemistry and operation of Kjeldahl method  Know 3 methods to analyze total soluble protein content – Biuret,lowry, UV Why are we interested in the total protein content of a food?  Consumer says: Protein is associated with nutritional quality; more protein means higher quality and higher price  Processor says: Protein means functionality (foaming, texture, emulsification, browning, color, and flavor); cost and quality Hydration properties Water-holding capacity Viscosity modifiers Solubility  Protein-Protein Interactions Gel formations Precipitation  Surface Properties Emulsifiers Foaming Bread making requires high-gluten flour  Disulfide linkages form, making a 3-D network within the bread dough. The term “functional foods” differ from protein functionality. Functional foods are foods and food components that provide a Functional foods are foods and food components that provide a health benefit beyond basic nutrition. - IFT health benefit beyond basic nutrition. - IFT ● Protein is analyzed for: ● nutritional labeling ● investigation of functional properties ● Protein analysis is required for you to know: ● total protein ● amino acid composition ● amount of a particular protein in a mixture ● Nutritional value of a protein ● Protein changes during storage & processing Why interested in protein changes due to processing and/or storage?  Heating may denature a protein (but gives a larger loaf volume for breads). Overheating generates toxic heterocyclic amine.  Decrease in nutritional quality  Loss in emulsification/foaming ability Milk, 3.2% Milk, 3.2% Dry milk, 24% Dry milk, 24% Egg, 12.6% Egg, 12.6% Soy, 36.5% Soy, 36.5% Beef, 21.4% Beef, 21.4% potato, 2% potato, 2% KJELDAHL METHOD Developed by Johann Kjeldahl in Developed by Johann Kjeldahl in 1883 and still used today (with 1883 and still used today (with some improvements) some improvements) The most common and well accepted method for The most common and well accepted method for determining total crude proteins (or total protein) determining total crude proteins (or total protein) in food. in food. ….(Kel-Dall) .(Kel-Dall) ● Proteins are composed of amino acids: there are 20 common α-amino acids (AA) ● AA are linked via peptide bonds and are composed of C, N, H, O and S ● The % N in a protein ranges from 13.4 to 19.1 %. The average % N in all proteins is 16% KJELDAHL – CHEMISTRY BASIS Proteins are MAJOR constituents of foods containing nitrogen...
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Ppt0000003 - Know 2 methods to analyze total protein...

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