The influence of ultrasound acoustic exposure on biosynthesis of exopolysaccharides and rheological properties of cultured milk foods obtained on the basis of kefir fungus

One of the leading development tendencies of Russian Federation food industry is implementing innovative methods in dairy raw materials processing technology. Ultrasonic cavitation is one of the perspective technologies for dairy raw material processing in dairy industry. Cultured milk foods produced on the basis of dairy raw materials reduced with the use of ultrasonic exposure are chosen as subjects of the research. The research showed that kefir souring on the kefir fungus starter progresses faster than in other samples: after (6 ± 0,5) hours of souring, titrable acidity of the mixture reached (85 ± 2) °Т. Intensive growth of titrable acidity allows reducing the souring period by 2-3 hours. Ultrasonic cavitation implementation on the stage of preparing dairy raw material for souring influences the blob stability to the spontaneous densifying of the structure: the biggest volume of isolated whey is observed among the samples, in which milk is processed in the ultrasonic exposure regime (60 % force, 3 minutes duration). The research results showed that using ultrasonic exposure in the raw milk processing regime of 3 minutes duration with the force equal 30 % in the technology of obtaining kefir with the use of kefir fungus leaven 1,4 times decreases whey isolation out of a blob, whereas for fermented milk drink on the basis of composite ferment the decrease is 1,5 times. During microscopic examination of constant preparations, it is revealed that the blobs obtained on the basis of kefir fungus symbiotic starter are characterized by homogenous consistency with lesser aggregates of dairy protein and bigger amount of protein complexes of small sizes, compared to the samples obtained on the basis of composite ferment containing the following cultures: Lac. lactis, Lac. cremoris, Leu. cremoris, Lactobacillus kefir, Аcetobacter subsp. аceti, Saccharomyces lactis. Dynamics of kefiran accumulation in fermented milk drinks is in direct relation with ultrasonic exposure regimes and starter cultures activity. Therefore, soluble polysaccharides accumulation in fermented milk drinks, as a factor determining their functional properties, is necessary to be regulated by the ultrasonic exposure regimes.