Variation of Total and Available Lysine in Dehydrated Products from Cheese Wheys by Different Processes

Excessive or prolonged exposure to heat during manufacture of dehydrated products from cheese whey and cheese whey protein concentrates is chiefly responsible for decreasing the lysine content of these products. With ion exchange chromatography of acid hydrolysates to determine total lysine, and 2,4,6,-trinitrobenzene sulfonic acid reagent to determine available lysine with its epsilon amino group free for chemical reaction, both total and available lysine were higher in spray-dried whey powders than in roller-dried whey powders. Of the lysine originally available in the protein of cottage cheese whey, 88% remained available in an experimental dehydrated high-protein isolate prepared by ultrafiltration, followed by gel permeation followed by pasteurization, vacuum evaporation, and shelf drying of the protein concentrate. Unfractionated foam spray-dried cottage cheese whey powder retained 96% of the original available lysine.