Influence of extraction conditions on characteristics of microbial polysaccharide kefiran isolated from kefir grains biomass

Kefiran is a water-soluble polysaccharide, which can be isolated from kefir grains biomass. Rheological behaviour and physico-chemical characteristics of kefiran solutions were influenced by the extraction parameters. Degradation of the polymer chain occurred at the highest temperature tested (100 degrees C). The intrinsic viscosity of kefiran solutions (0.1 g.ml(-1)) varied between 8.24 mPa at 100 degrees C to 19.32 mPa at 80 degrees C. Regarding rheological properties, kefiran solutions had characteristics of a Newtonian behaviour in diluted solutions and pseudoplastic at higher concentrations. High-performance liquid chromatography analysis of monosaccharides revealed that kefiran is composed of glucose and galactose in a relative molar ratio of 0.94-1.1. Infrared spectra of kefiran suggested the structure of alpha- and beta-configurations in pyranose-form carbohydrates, which indicated a purified structure of kefiran. The molecular weight of kefiran polymer was between 2.4 x 10(6) Da and 1.5 x 10(7) Da, the values of molecular weight depending on extraction conditions. This polysaccharide was found to have higher intrinsic viscosity and higher apparent viscosity in aqueous solutions, which brings a perspective for its use as thickening or gelling agent in food, or as a matrix in film-forming solutions.