Influence of refrigeration and carbon dioxide addition to raw milk on microbial levels, free monosaccharides and myo-inositol content of raw and pasteurized milk

The influence of CO2 treatment on free monosaccharides and myo-inositol in raw and pasteurized milk during cold storage was studied. Pasteurization di d not cause significant changes in the monosaccharide fraction. No variatio ns in the level of galactose and myo-inositol in untreated and CO2-treated samples were observed during cold storage. The content of glucose decreased considerably during cold storage due to bacterial growth in pasteurized mi lk. During cold storage of pasteurized milk no changes in N-acetylgalactosa mine were observed, whereas N-acetylglucosamine decreased considerably afte r 15 days. No differences between untreated and CO2-treated milks were foun d. A substantial decrease in N-acetylglucosamine and a gradual increase in N-acetylgalactosamine were observed in raw milk during cold storage. The fo rmer was attributed to consumption of this hexosamine by microorganisms and the latter was probably due to microbial glycosidic enzymes. The addition of CO2 to raw milk proved to be a useful treatment for milk preservation wi thout modifying the free monosaccharide fraction.