CHANGES IN THE PROTEIN AND CARBOHYDRATE PROFILE OF KEFIR BEVERAGE, ACQUIRED FROM KEFIR GRAIN OF UNKNOWN ORIGIN

The purpose of the present study was to compare the nutritional quality of kefir, produced from kefir grains of uncontrolled origin to commercially available kefir beverage. Two-dimensional protein electrophoresis (isoelectrofocusing, followed by SDS PAGE) was used to compare protein profiles at different stages of the fermentation process. Carbohydrate profile was studied by thin layer chromatography. Both proteins and carbohydrates were determined quantitatively with colorimetric methods. The resulting beverage showed similar to the commercial kefir properties in term of pH, protein and reducing sugars content between the 24th and 36th hour of fermentation. No significant change in the protein profile on 2D electrophoregrames was found up to the 24th hour and the following reduction of protein spots was mainly attributed to protein precipitation rather than digestion to smaller peptides. Unlike commercial kefir, no galactose or other monosaccharides were found even after 36 hours of incubation suggesting different properties. Our study showed an efficient and low-cost methodology for characterization of fermented milk products. The kefir beverage, investigated in this particular study proved to possess slightly different characteristics than the commercially available and showed the necessity of a quality control.