DEPENDENCE OF LACTOBACILLI ACTIVITY ON THE CONCENTRATION OF SUGAR IN THE SUBSTRATE

Abstract

The purpose of the article was to extend the shelf life of birch sap and the time of its processing by pre-fermentation of birch sap with pure crops Lactobacillus casei ssp. alactosus. The disadvantage of the existing method of production of birch sap is that the newly collected birch sap must be immediately sent for processing, because short-term storage for no more than 24 hours is allowed only in chilled rooms at a temperature of 0 to 5 0C and a relative humidity of not more than 75 %. In case of violation of these conditions, turbidity of the juice appears, acidity increases and spontaneous fermentation of the juice begins, which has significant flaws. The sugar content in birch sap is relatively low. Since the fluctuations in the sugar content of fresh juice are quite significant, it was necessary to identify the activity of its costs during the fermentation process. Research methodology. The activity of lactobacilli was determined by measuring the loss of dry soluble substances in the juice during fermentation and the accumulation of titrated acids in terms of lactic acid. Results. Fluctuations in sugars depending on weather conditions and place of cultivation range from 0.5 to 0.9 %. The final product of sugar fermentation with lactobacilli, as already noted, is mainly lactic acid and other substances (acetic acid, ethyl alcohol, carbon dioxide, dextrin, mannitol) in small quantities. The term fermentation of birch sap to the desired lactic acid content can be adjusted by adding a certain amount of sugar to it. According to the derived regression equations, it is possible to predict on which day and at what concentration in the juice the desired acidity will be. The concentration of titrated acids in terms of lactic acid changed during the entire fermentation period, which occurred in rectilinear dependence, which is confirmed by the correlation coefficients Conclusions. To activate lactic fermentation with a small amount of sugar, it should be added to freshly harvested birch sap.