FDSC 300 Lecture 6: protein analysis
20 Oct 2017
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Properties/processing: protein content affect properties of food (ex: gelatin, gluten); role in processing; how they will interact. %crude protein = total n x conversion factor (proximate analysis = crude protein: *total n is not all from protein; some from urea, nitrates, nucleic acid, b vitamins, amino sugars, adulterants, etc (non-protein n) Kjiedahl: (still standard!) convert n -> nh3: digestion: use h2so4 -> trap n as ammonium sulfate (turns yellow) c and h are lost as vapor. Use se or cu to speed up (catalyst) Use potassium sulfate to increase bp (not boil over: distillation: add salt (naoh, koh) -> release ammonia -> heat and distill into. Add more salt to increase ph to 9. 2 (turn nh4 back into nh3) Add na thiosulfate -> release trapped ammonia from metals: titrate w/ hcl (mol hcl = mol n)
