Nutritional and Chemical Evaluation of the Protein Fraction from Fermented Ammoniated Whey

Abstract

Whey from cottage cheese was fermented with Lactobacillus bulgaricus at 43 C and pH 5.5 (ammonia was added continuously to maintain the pH), and the fermented product was fractionated by dialysis into a protein fraction containing whey proteins and bacterial cells and an ammonium lactate fraction. The protein fraction was concentrated by evaporation, lyophilized, contained 95.5% total solids, 64.4% crude protein, 6.9% lactose, and had a gross energy of 5.5 kcal/g. Approximately 91.6% of crude protein in protein fraction was hot trichloroacetic acid precipitable or true protein. The modified essential amino acid index and in vitro protein digestibility of protein fraction were 99 and 92.4%. Based on feeding trials with rats, protein fraction had a protein efficiency ratio of 4.1 ± .15 which was higher than the protein efficiency ratio of 3.34 ± .26 for casein. Protein fraction is a potentially valuable protein supplement for humans. The ammonium lactate fraction, concentrated by evaporation to 32° Baume, contained 63.9% total solids, 53.8% crude protein, .6% lactose and had a gross energy of 3.5 kcal/g. The trichloroacetic acid soluble nitrogen accounted for 99.9% of the total nitrogen in ammonium lactate fraction of which 74.4% was ammonia nitrogen. The ammonium lactate fraction is a potential nonprotein nitrogen supplement for ruminants. © 1977, American Dairy Science Association. All rights reserved.