Ppt0000003 - infoodsKjeldahl&Dumas Kjeldahlmethod...

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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
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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  
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Hydration properties  Water-holding capacity Viscosity modifiers Solubility Protein-Protein Interactions Gel formations Precipitation Surface Properties Emulsifiers Foaming
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Bread making requires high-gluten flour Disulfide linkages form, making a 3-D network  within the bread dough.
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The term “functional foods” differ from protein  functionality. Functional foods arefoods and food components that providea Functional foods arefoods and food components that providea health benefit beyond basic nutrition. - IFT health benefit beyond basic nutrition. - IFT
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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
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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
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Milk, 3.2% Milk, 3.2% Dry milk, 24% Dry milk, 24% Egg, 12.6% Egg, 12.6% Soy, 36.5% Beef, 21.4% Beef, 21.4% potato, 2% potato, 2%
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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)
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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
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Proteins are MAJOR  constituents of foods  containing  nitrogen , and N is largely unique to  protein.
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