Microbiological evaluation of the quality of dry leaven, which are sold in the commercial networks of the city of the Dnipro

Abstract

The results of the study of dry starter cultures used for the manufacture of yogurt are presented. Аfter 6 hours of research the high activity of starter cultures “VIVO” (homogeneous consistency of dense сlot with pure tender pleasant juicy taste and pronounced aroma) is established, the average activity of ferment “GENESIS” (semi-solid clot, not pure sour-milk taste and medium aroma) and low – “GOODFOOD” (no clot, astringent aqueous-mucous consistency of mass, sweet to taste with moderate aroma). The smell and taste of the formed clots of all three starter cultures was characteristic of yogurt. The test for the presence of carbon dioxide gas was negative in all samples, indicating the absence of microorganisms capable of gas formation and the destruction of the сlot that formed. The titrated acidity of the starter cultures “VIVO” and “GENESIS” was 80 °T and corresponded to normative indicators, while “GOODFOOD” was on the lower limit of the norm (65 °T). With prolonged storage of starter cultures (during 5 months at 4 °C), their activity decreased by almost 2 times. In this case, after 12 hours of fermentation in the of the samples of starter cultures “VIVO” and “GENESIS” found a pronounced sour taste, in “GOODFOOD” – the latter was moderately sweet. Increasing the time of fermentation leads to the accumulation of lactic acid. The lower activity of the “GOODFOOD” leaven is due to the predominance of lactic streptococci in its composition, which contribute to the formation of a thick clot of viscous consistency and with a delay (8 hours), in comparison with the starter cultures “VIVO” and “GENESIS”.Non-dairy bacteria in aerobic conditions were detected in the study of starter cultures “GOODFOOD”, in anaerobic conditions – in the starter cultures “GENESIS”. Also in leaven “GENESIS” is installed cells of yeast-like fungi. Іn the medium Saburo, on the 5th day after sowing, there were small, convex white colonies that had a shiny surface and smooth edges. Chlamydospores and pseudomycelium were detected by microscopy. There was no change in color and gas formation in the MacConkey broth: floats that were placed in the test tubes the remained on the bottom, indicating the absence of bacteria the E. coli in the starter cultures. Such non-dairy microorganisms refer to technically harmful microflora, which can lead to the appearance of defects and a decrease in the quality of the finished product, because can cause profound destruction of proteins.