Viability and Proteolytic Capacity of Lactobacillus bulgaricus 2772 and Lactobacillus rhamnosus GG during Cheese Ripening

Nowadays, probiotics have been utilized as starter cultures in the elaboration of fermented dairy products such as cheese. The survival of probiotic microorganisms in this type of products is very important in order to have a beneficial effect after their consumption. In addition to this, milk proteins are considered an important source of bioactive peptides. These peptides have been identified in hydrolyzed products of milk proteins and dairy products such as cheese. In this study, the protective effect on the survival of Lactobacillus rhamnosus GG was determined in a cheese which was inoculated only with this probiotic microorganism, and in another cheese additionally inoculated with Lactobacillus bulgaricus 2772 (exopolysaccharide producer bacteria). The ripening of these cheeses took place for 28 days at two different temperatures (4°C and 14°C). The proteolytic capacity was analyzed by measuring the concentration of free amino groups, through the trinitrobenzenesulfonic acid method (TNBS). The separation of peptides was carried out by polyacrylamide gel electrophoresis (SDS-PAGE) with 15% T. At the end of the study it was found that the population density was higher in the cheeses ripened at 14°C while at 4°C, it decreased. A higher proteolytic activity at 14°C was also observed and it was determined by a higher concentration of free amino groups. Likewise, during the analysis of electrophoresis gels, a higher concentration of peptides smaller than 10 kDa was found in the samples of cheeses ripened at 14°C. These results increase the expectations to find peptides with a biological function.