Study of Chemical and Microbial Properties of Probiotic Quark Cheese Containing Lactobacillus Acidophilus and Lactobacillus Casei

The aim of this study was to investigate chemical and microbial properties of probiotic Quark cheese containing L.acidophilus (LA) and L.casei (LC) during 21 days of storage. Results showed that LC sample had significantly lower pH than that of both LA and control. pH values of all samples decreased significantly upon storage time. Treatable acidity changes in cheese sample was similar to pH change, although acidity differences between samples was more enhanced than pH variation. There was a significant increase in soluble nitrogen of LC sample compared to that of LA and control in Day 21. Increasing storage time from 7 to 21 days, significantly increased the soluble nitrogen content of all cheese samples. Increasing storage time significantly increased lipolysis index of control compared to probiotic chees samples. Coliform counts was negligible in all samples and was below 10 log CFU/g in probiotic cheese samples. Yeast and mold counts of control was significantly higher than that of probiotic samples. Lactobacilli count results indicated that the number of viable bacteria in both probiotic cheese samples was 8.5-8.6 log CFU/g in day 1. Increasing storage time up to 21 days did not significantly (p<0.05) decrease the number of lactobacilli and in both probiotic samples it remained above 8 log CFU/g. Quark cheese provided a good substance for the incorporation of probiotic strains. Storage of quark cheese until 21 days preserved probiotic bacteria and resulted in the desired chemical properties.