Characteristics of volatile flavor components in traditional fermented yak milk produced in different ecoregions of the Qinghai-Tibetan plateau

The volatile flavor substances in traditional fermented yak milk samples collected from 5 ecoregions (A: coniferous forests and grasslands of the Qilian Qingdong Mountains; B: alpine grasslands surrounding the lakes in the Qiangtang Plateau; C: alpine shrubs and meadows of the Guoluo-Nagqu Highlands; D: coniferous forests along the alpine valley in East Tibet; E: shrubs and grasslands along the alpine valley in South Tibet) of the Qinghai-Tibetan plateau were comparatively analyzed. The relative percentage composition of volatile flavor substances varied among the different ecoregions. In samples collected from region E, more than 50% of the volatile flavor compounds were esters comprising mainly n-butyl acetate, butyl butyrate, and ethyl octanoate, and a considerable proportion of acetoin was found in samples from regions B and E. Greater proportions of 2-heptanone and 2-nonanone were observed in samples collected from regions A, C, and D compared with regions B and E.