A survey on chemical and microbiological composition of kurut, naturally fermented yak milk from Qinghai in China

Thirty-two batches of samples of kurut (naturally fermented yak milk) were collected at four locations in Qinghai, China, and their chemical and microbiological composition was analyzed. Average levels of major components were: total solids 14.3 ± 1.52 g/100 ml, fat 5.37 ± 1.04 g/100 ml, total protein 5.44 ± 1.06 g/100 ml, lactose 2.34 ± 0.172 g/100 ml, ash 0.860 ± 0.080 g/100 ml and titratable acidity 158 ± 16.3 °T. Results showed that the kurut had richer nutrients than the yoghurt. The HP (kurut samples from Plateau yaks in the northwest of Qinghai) had better chemical nutrients density than the MH (kurut samples from Huanhu yaks in the south of Qinghai) and LH (kurut samples from Huanhu yaks in the east of Qinghai). Sodium dodecyl sulfate–PAGE and densitometry analysis results demonstrated that kurut was rich in casein, immunoglobulins, serum albumin, β-lactoglobulin, α-lactalbumin, and two unknown fractions in part samples. Microbiological enumeration revealed that the kurut contained larger lactic acid bacteria and yeast than those of the traditional fermented milk referred, with the average counts of lactic acid bacteria of 9.18 ± 0.851 log cfu/ml and the yeast 8.33 ± 0.624 log cfu/ml. The lactic acid bacteria dominated in the HP and LH kurut while the yeast dominated in MH kurut. The kurut was judged nutritional and indicates the latent value for people’s health.