The aim of the research was to study the dynamics of active and titratable acidity with a low and high initial titer, while cultivating white head cabbage of the variety ‘Parus’ with lactic acid bacteria Leuconostoc lactis VKPM V-12150 and Leuconostoc mesenteroides subsp. mesenteroides VKPM V-8818 in the basic model medium (BMS) and the modified model medium (MMC) during fermentation . In this experiment, two important questions were considered: the creation of favorable conditions for the growth of lactic acid microorganisms and the suppression of undesirable pathogenic microflora, which can eventually lead to product spoilage. One of the key questions is to scale the results of studies related to the fermentation of plant objects by microorganisms on initially non-sterile raw materials that is the requirement to create as possible fast the conditions that restrain the reproduction of Cl. botulinum, preventing toxin accumulation in the product. Therefore, an important factor is the observance for the necessary boundary condition where for international standards, it reaches pH ≤ 4.6, and for Russian standards it reaches pH ≤ 4.2. Hence, an analysis of the experimental data showed that these boundary conditions were reached after the expiration of essentially different time intervals during the cultivation of microorganisms with different starting titers. As a result, it was shown with which lactic acid microorganisms the optimal parameters for the dynamics of active and titratable acidity were obtained, when the boundary condition reached pH 4.2. Since this value determines more "stringent" requirements for product safety. As a result of studies it was found that optimal parameters for the dynamics of active and titratable acidity when a limit pH value of 4.2 is obtained in the cultivation of lactic acid bacteria L. mesenteroides in the MMC, revealing that the value of the starting titer ranging from 3*103 to 3*105 CFU/g.

The article presents the results of the study of the directed fermentation of cucumbers using strains of lactic acid microorganisms (lactic acid bacteria) in order to intensify the fermentation process and to obtain a finished product of good quality (with good taste, aroma and structure), as on an industrial scale starter cultures are practically not used. The aim of our research was to study the dynamics of glucose degradation in the process of directed fermentation of cucumbers varieties "Vodoley" using lactic acid bacteria and their selection for this process. As strains of lactic acid microorganisms we selected the following: Lactobacillus casei VKM 536, Lactobacillus plantarum VKM V-578, Lactobacillus brevis VKM V-1309. In order to create optimal conditions for the development of the target microflora, to determine the degree of glucose destruction by various strains of microorganisms and to obtain comparative results, all experiments were carried out on model environment. During the research, mathematical models were developed that adequately describe the degree of glucose destruction during the fermentation of cucumbers. Mathematical processing of glucose degradation data in the direct fermentation process was carried out using Microsoft Excel and the SYSTAT TableCurve 2D. It was found that the criterion for the intensity of glucose destruction during the fermentation of cucumbers varieties "Vodoley" is the most adequate use of the investigated strains of lactic acid bacteria L. brevis and L. plantarum. The use of these lactic acid bacteria provides maximum process efficiency (the maximum acceptable duration is 4,47 and 5,36 days when the degree of glucose destruction is more than 99% of the asymptotic value). The use of L. brevis and L. plantarum allows to achieve the maximum degree of glucose destruction, which indicates the potential usefulness of these types of lactic acid bacteria.