Effect of high pressures on microflora of commercial kefir culture

摘要

Kefir obtained from the commercial kefir culture, and its lyophilised components, after 24-hour cultivation in milk, were subjected to high pressures in the range of 200-1000 MPa, at an ambient temperature, for 15 minutes. Lactic streptococci were then added to skim milk and incubated at 25°C, whereas kefir and yeasts were added to milk with various additives, commonly used in dairy products, and stored at 4°C or incubated at 25°C, respectively. In all samples, before and after pressurization, the number of living microorganisms and acidity were periodically determined. The decrease of both viability and acidifying activity of kefir grain microflora together with the rise of the applied pressure was observed. It was also stated that additives used in the experiment had a protective effect on kefir microflora and yeasts exposed to the pressure of 400 MPa.