Chramostová J., Mošnová R., Lisová I., Pešek E., Drbohlav J., Němečková I. (2014): Influence of cultivation conditions on the growth of Lactobacillus acidophilus, Bifidobacterium sp., and Streptococcus thermophiles, and on the production of organic acids in fermented milks. Czech J. Food Sci., 32: 422-429.The parameters influencing the formation of organic acids and the ratio between the optical isomers of lactic acid were evaluated. Five different factors were tested, namely the form of starter, inoculum, temperature of fermentation, time of fermentation, and enhanced non-fat dry matter or addition of whey protein concentrate. Out of them, optimal conditions were chosen for the preparation of fermented milk beverage with ABT culture (Lactobacillus acidophilus, Bifidobacterium sp., Streptococcus thermophilus) with a lowered content of d(-)-lactic acid. The inoculum of bifidobacteria had the only significant effect on the ratio between lactic acid isomers. When 1% v/w used, the ratio of d(-)-lactic acid to l(+)-lactic acid was 0.05. When 5% v/w used, the ratio was 0.02. The addition of dried skimmed milk (max. effect at 12% w/w) enhanced the growth of bifidobacteria, while whey protein concentrate was effective for the growth of lactobacilli. The optimal temperature and time of cultivation were 37°C and 17 ± 0.5 h, respectively.

Chramostová J., Hanuš O., Klimešová M., Němečková I., Roubal P., Kopecký J., Jedelská R., Nejeschlebová L. (2016): Proteolysis in raw milk in relation to microbiological indicators. Czech J. Food Sci., 34: 306-312.Proteolysis in raw milk is a crucial parameter indicating both cow's mastitis and the technological problems or spoilage risk of final products. However, a suitable analytical method for its early detection in practice is still missing. Thus, we proposed a spectrophotometric determination of milk proteolysis equivalent (MPE). We tested this method on 104 bovine raw milk samples in relation to their somatic cell count (SCC) as an indicator of native proteolysis, and the total count of mesophilic bacteria (TCMB) and the total count of psychrotrophic bacteria (TCPB) as indicators of microbial proteolysis. Correlation coefficients between log TCMB and MPE and log TCPB and MPE were 0.3651 and 0.4152, respectively (both P < 0.001). SCC was not correlated with MPE (P > 0.05). We estimated the MPE limit indicating an incipient risk of proteolysis in the range from 0.9366 to 1.02 mmol/l. The determination of MPE seems to be a promising method applicable in the control of raw milk.