The effect of starter on amino acid composition of fermented milk

The experimental studies of the amino acid composition of the skimmed cow milk fermented with kefir corns, natural kurunga symbiotic starter and bacterial concentrate of the microbial consortium (BСMC) have been carried out. The bacterial concentrate of the microbial consortium is intended for the preparation of a fermented milk beverage of mixed fermentation – kurunga. The microbial consortium obtained by autoselection of population of kefir corn starter and thermophilic lactobacteriums Lactobacillus bulgaricus and Lactobacillus acidophilum has been used to prepare BCMC. The amino acid analysis of the samples has been carried out by IC method with postcolumn derivatization of amino acids ninhydrin in the acid hydrolyzate of the sample on INGOSAAA-400 amino acid analyzer. The most of essential amino acids has been found in kefir – 434 mg/g of protein. In the samples prepared with natural starter and bacterial concentrate, the total amount of essential amino acids has been 401.84 and 403.8 mg/g of protein, respectively. Exogenous amino acids are essential for the growth of lactics and yeast. The difference in the total amount of the essential amino acids in the samples, probably, caused by the proteolytic activity of the starters and the growth requirements of the microorganisms. The assessment of the bioavailability has been carried out by the method of I.A. Rogov and N.N. Lipatov according to the coefficients of differences between the amino-acid score (CDAS) and bioavailability. The amino-acid scoring studies have shown that the protein in the studied samples is characterized by a complete composition. According to bioavailability, the kurunga samples exceeded kefir by 0.55-0.75%. The obtained results indicate that according to the biochemical activity, the bacterial concentrate of the microbial consortium is practically identical to kurunga prepared with natural starter. It makes possible to obtain a product bioavailably identical to a traditional beverage