Microbiological and chemical investigations on Sugar Kefir drink

Five beverages obtained from different grains and a control drink, prepared using the same ingredrents but without the grains, were microbiologically and chemically analysed. The analyses were performed on the beverages as soon as prepared and, at fixed times, during storage at 5°C. Lactic acid bacteria and yeasts were the dominant microbial forms, the presence of acetic acid bacteria was negligible and no other microorganisms were found. Lactic acid bacteria are represented by facultative heterofermentative forms, especially Lactobacillus casei and its subspecies, while Saccharomycex cerevisiae and Hansenula yalbensis represented the yeasts. Lactic acid bacteria are principally responsible for the grain syntesis. In fact they are able to begin the production in presence of dried fruits and sugar. More variable and less standardized is the quantitative chemical composition. It is closely connected to the metabolic activity of the strains, preparation conditions and storage time. The substances found in large quantities are lactic acid and ethanol coming respectively from bacteria and yeasts metabolism.