Study of the kinetics of the fermentation process of soy milk by starter culture Lactobacillus acidophilus

Fermented dairy products are the most commonly used food matrix for the production of probiotic drinks; however, the presence of a large number of consumers with lactose intolerance makes it necessary to develop plant-based probiotic drinks. Soy milk in its natural form contains approximately the same amount of protein as cow's milk but differs from it in the composition of amino acids. It is also characterized by a low content of saturated fat and the absence of cholesterol. A number of studies have shown that fermentation with probiotic bacteria improves the functional characteristics of soy milk through the formation of antihypertensive peptides, contributing to the normalization of the intestinal tract and reducing the content of indigestible oligosaccharides. The purpose of this study was to study the possibility of soy milk fermentation with a monocultural starter culture of Lactobacillus acidophilus and to evaluate the kinetics of the enzymatic process. Evaluation of the efficiency of the fermentation process was carried out by determining the pH and titratable acidity after equal periods of time, as well as the accumulation of lactic acid during fermentation. The results obtained showed that in all the studied samples, there was a gradual decrease in the pH values of the product. The range of changes for different samples varied from 0.4 to 0.6. The results indicate the most active course of the fermentation process in the vegetable drink “Healthy Menu”, The highest value of titratable acidity at the end of fermentation was recorded for sample ZM-32 (27.1 deg). Moreover, this process is significantly affected by the temperature of the process. The amount of accumulated lactic acid in the system of vegetable drinks at the end of the estimated fermentation period was 20.22-29.6 %, which indirectly indicates the adaptation of Lactobacillus acidophilus in the soy milk environment. Using regression analysis, mathematical models were obtained that adequately describe the process of accumulation of lactic acid depending on the temperature and duration of the fermentation process.