Patterns of changes in the properties of a fermented milk drink with Lactobacillus acidophilus from the molecular weights of chitosans

Abstract

Chitosan can be used to extend the shelf life of fermented milk products with Lactobacillus acidophilus. This cationic polysaccharide in the protonated state has a positive charge. Due to this, it is able to interact with the cell walls of lactobacillus, which have a negative charge. The effect of oligochitosans with molecular weights of 7,0 kDa, 25,4 kDa, 45,3 kDa and chitosan 350 kDa at concentrations of 0,0025, 0,005, 0,0075 and 0,01 per cent on the process of cultivation and long-term storage of fermented milk product with L. acidophilus was studied. In the control and experimental samples, it was determined: active and titrated acidity, lactic acid, lactose and the number of lactic acid microorganisms. The average rate of lactic acid synthesis and the average daily decrease in the number of cells (CFU/g /day) during 17 days of storage were calculated. It is shown that in the process of cultivation, in comparison with the control, oligochitosans (OC) and chitosan in the studied concentrations do not affect the active and titrated acidity. During long-term storage, for 17 days, fermented milk products containing oligochitosans are characterized by active and titrated acidity, lactic acid and lactose concentrations close to control. The average rate of lactic acid synthesis was close to the control and was 2.8*10-3 - 7.7*10-3 mol/l/day. In the fermented milk product, high-molecular chitosan (HC) in comparison with the control caused higher pH values and a significant decrease in titrated acidity. The average rate of lactic acid synthesis on the 17th day of storage, depending on the concentrations of HC: 0,0025, 0,005, 0,0075 and 0,01 per cent, decreased by 1,89; 3,8; 3,5; 3,5 times, respectively, compared with the control. On the 17th day of product storage, the number of viable lactobacillus was 2,1×109 CFU/g, which is 20 times higher than the recommended minimum therapeutic dose, which is 108 CFU/g. For the preparation of fermented milk products with L. acidophilus, with a long shelf life, it is recommended to use high-molecular chitosan in concentrations of 0,005, 0,0075 and 0,01 per cent.