Influence of Lactose Hydrolyzation on Properties of Yogurt and Sour Milk

The effect of lactose hydrolysis on the properties of fermented milk products has been studied. The following sour-milk products were used to produce experimental samples: lactose-free milk obtained by enzymatic hydrolysis using «Bonlacta™» (15250 SDLU/g, IFF Nutrition & Biosciences Inc., USA); sourdough consisting of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus salivarius subsp. thermophilus (yogurt) and St. salivarius subsp. thermophilus (sour milk/ prostokvasha). Sour milk and yogurt produced with the same starters but with conventional milk were used as controls. Lactose-free yogurt produced had a stronger clot, fewer viable cells, longer fermentation time and lower titratable acidity compared to the control yogurt. The viscosity of the lactose-free product was slightly different from that of the control. The lactose-free yogurt was also found to have a stronger clot and slightly lower titratable acidity. However, unlike yogurt, the viscosity of the lactose-free sour milk was higher than that of the control, and the duration of fermentation as well as the number of viable cells were the same. Nevertheless, both lactose-free products complied with the Technical Regulation of the Customs Union 033/2013