摘要：The aim of the study was to investigate the effects of prepared classic working starter culture as compared with starter culture to be added direct-to-vat in frozen form, on quality and yoghurt's permanence of shelf-life. In 3 laboratory-scale experiments 9 yoghurt samples were prepared using classic working starter culture and 9 samples using freeze-dried direct-set starter culture. Analysis of prepared yoghurt samples included determination of: active acidity (pH), total bacterial counts as well as counts of Lactobacilli and Streptococci in 1 ml of sample. Variation of acidity was observed during 8 days' keeping of yoghurt samples in refrigerator (+8 °C). Counts of viable bacterial cells in yoghurt were greater when freeze-dried direct-set starter culture was used for milk incubation, but acidity was not implied. Acidity of yoghurt samples increased after 8 days of keeping in refrigerator in case when freeze-dried direct-set starter culture was used. Also, the acidity of mentioned samples was greater than acidity of yoghurt samples prepared using classic working starter culture. Using freeze-dried direct-set starter culture did not prolong significantly the incubation time of inoculated milk.
关键词：yoghurt preparation; classic working starter culture; freeze-dried direct-set starter culture; quality of yoghurt; yoghurt's permanence of shelf-life
