Microbiological, physicochemical and organoleptic characteristics of probiotic Bulgarian yoghurts obtained by an ultrafiltered whole cow’s milk

Abstract

Ultrafiltration of whole cow’s milk with ultrafiltration polyacrilonitrile membrane with 10 kDa molecular weight cut-off at volume reduction ratios 2 and 3 was performed. The obtained ultrafiltration retentates were used for production of probiotic Bulgarian yoghurts with three different starters. A control sample was prepared using whole cow’s milk with the same starters. All yoghurts were analyzed according to the following parameters: titratable acidity, dry matter, organoleptic characteristics, concentration of specific microorganisms, Lactobacillus bulgaricus and Streptococcus thermophilus, as well as the total count of viable lactic acid bacteria for 28 days of storage. The results showed that the increase in the volume reduction ratio during ultrafiltration increased the titratable acidity, as well as the dry matter of all examined yoghurts. The level of ultrafiltration concentration led to an increase in the viable lactic acid bacteria in all tested yoghurts which improves their functional properties.