关键词: 藏灵菇, 胞外多糖, 发酵性能, 切达干酪

Abstract: The exopolysaccharide (EPS) yield of Tibet kefir KW1 grown in SDM medium at 37 ℃ was 624.82 mg/L. The EPS was separated and purified, and it was determined to be composed of rhamnose, arabinose, mannose, glucose and galactose in a molar ratio of 1:3.02:2.12:1.59:3.04. Infrared spectroscopy showed that the EPS exhibited a typical absorption peak pattern of polysaccharides. Under scanning electron microscopy, the EPS exhibited spherical and flaky structures with a surface smooth. Observation by atomic force microscopy showed aggregates with membrane-like and cluster-like structures. When applied in milk fermentation and Cheddar cheese production, the EPS promoted the growth of the starter culture, and this effect initially increased and then decreased with increasing its concentration. Addition of the EPS increased the yield of cheese, the water-holding capacity and the number of viable bacteria during ripening. A total of 69 volatile flavor compounds were detected by gas chromatography-mass spectrometry (GC-MS). The calculation of odor activity value (OAV) showed that a total of 17 flavor substances contributed to the overall flavor of the cheese, among which ethyl butyrate, ethyl hexanoate and ethyl octanoate were the key flavor substances. The present research can provide a technical basis for the application of the EPS from Tibetan kefir in fermented milk products.

Key words: Tibetan kefir, exopolysaccharide, fermentation properties, Cheddar cheese