ДИФФЕРЕНЦИАЛЬНО-ТЕРМИЧЕСКИЙ АНАЛИЗ В ОЦЕНКЕ ЭКЗОПОЛИСАХАРИДНОЙ АКТИВНОСТИ КОНСОРЦИУМОВ ПРОБИОТИЧЕСКИХ МИКРООРГАНИЗМОВ

Abstract

Microbial polysaccharides with high moisture-binding activity synthesized during the growth of probiotics are known to improve such technological properties of dairy products as resistance of milk gels to syneresis, as well as the adaptive properties of probiotic microorganisms and their adhesion to the mucosal surface of the gastrointestinal tract. In this paper, we present the results of an experimental study carried out to investigate the synthesis of microbial polysaccharides by means of probiotic consortia based on an assessment of changes in the content and ratio of bound moisture. The state of moisture in fermented probiotic products was evaluated by differential thermal analysis using a Synchronous Thermal Analyzer, as well as by the thermogravimetric analysis, differential scanning calorimetry and non-isothermal kinetic methods. Research samp-les included lowfat fermented probiotic milk-vegetable systems containing the following microbial consortia: No. 1 - Str. thermophilus, L. сasei subsp., L. rhamnosus; No. 2 - Str. thermophilus, L. acidophilus, L. plantarum, L. fermentum; No. 3 - Str. thermophilus, B. bifidum, B. longum, B. adolescentis; No. 4 - Str. thermophilus, L. сasei subsp., L. rhamnosus, L. acidophilus, L. plantarum, L. fermentum, B. bifidum, B. longum, B. adolescentis, all taken at a concentration of 109 CFU/mL. A mixture of the Vitazar, Flarabin, and Flavocen dietary supplements was used as a biologically active plant component. Reference samples consisted in skimmed milk and casein gel, with the latter being obtained by the acid coagulation of skimmed milk using concentrated hydrochloric acid. The process of dehydration in the reference samples of skimmed milk and casein gel is shown to occur within a more narrow temperature range compared to those of the fermented systems. This indicates an increase in the content of bound moisture in these systems resulting from the synthesis of exopolysaccharides by probiotic microorganisms. A quantitative assessment of moisture fractions characterised by different types of bonding was performed using experimental curves obtained by the TGA method. The ranges of endothermic effects, indicating a stepwise removal of moisture, have been determined in accordance with the form and energy of the association of moisture with the experimental sample biopolymers. The obtained results demonstrate a pronounced exopolysaccharide activity on the part of the probiotic consortia under study.