Study of the fermentation process of milk base with increased protein content in the presence of dihydroquercetin

The experimental studies have been carried out in the Vologda region. The objects of study are milk base with a protein content of 5%, enriched with dihydroquercetin and fermented with Lactobacillus acidophilus and Streptococcus thermophilus microorganisms. The milk base has contained buttermilk and protein concentrate derived by fractionating of buttermilk with apple pectin. The variable parameter has been the amount of dihydroquercetin. The aim of the work is to study the fermentation process of a milk base containing buttermilk and protein concentrate derived by fractionating of buttermilk with a polysaccharide (hereinafter referred to as the milk base) in the presence of dihydroquercetin. For this purpose, the functional ingredient powder has been added before pasteurization to the milk base samples in different amounts: 7.5 mg of dihydroquercetin per 100 g of product; 12.5 mg of dihydroquercetin per 100 g of product; 25.0 mg dihydroquercetin per 100 g. One sample has been taken as a control one without adding dihydroquercetin. After cooling the milk base to the fermentation temperature, a starter culture based on Lactobacillus acidophilus and Streptococcus thermophilus has been added in an amount of 5% of the mixture weight, then the fermentation process has been studied. During the study, no noticeable differences in the rate of titratable acidity increase or in active acidity decrease have been found between the control and experimental samples. Determination of the specific electrical conductivity (SEC) during the fermentation of the samples have shown that in the first hour of fermentation, the SEC rose quite slowly by (0.08-0.36) mS/cm, in the third hour it has increased sharply by (1.25-1.35) mS/cm and has been increasing until the end of fermentation. The determinations of the specific electrical conductivity correspond to the reproduction phases of lactic acid microorganisms, which allows using this indicator for indirect establishment of their development. Examination of the amount of lactic acid bacteria in the mixture after adding the starter and in the finished product has shown that dihydroquercetin does not affect the development of acidophilus bacillus or thermophilic streptococcus. Determination of the synergetic capacity of clots has shown its dependence on dihydroquercetin amount. The volume of separated whey has been low and amounted to 1.2–2.8%. The apparent increase in the water-holding capacity of clots as the dihydroquercetin content in the milk base increases may be due to the formation of bonds between the components of buttermilk and dihydroquercetin.