Comparative study of the physicochemical properties, volatile compounds, and bacterial microbiota in commercial and traditional yak yogurt from the Qinghai-Tibet plateau.

This study aimed to elucidate differences between the commercial starter culture (CK) and traditional starters from different Tibetan regions (Gannan (GN), Qinghai (QH), Tibet (XZ)) in fermenting yak yogurt by physicochemical properties, flavor, and bacterial community. Results indicated acidity, proline, arginine, alanine, and C6:0 contents were significantly higher in the traditional starter culture than CK (P < 0.05). Gas chromatography-ion mobility spectrometry analysis found the traditional starter culture group was dominated by alcohols and esters, whereas CK exhibited richer ketones. Metagenomic analysis revealed Lactobacillus delbrueckii (49.56% in XZ, 24.86% in GN) and Streptococcus spp. (18.30% in CK, 17.21% in QH) as the dominant. Moreover, pH and titratable acidity were primary factors affecting microbial diversity. Meanwhile, glutamic acid modulated ester biosynthesis like ethyl acetate, while C16:0 fatty acids inhibited off-odor ketones such as 2-pentanone. This study offers valuable insights into developing specialized fermentation agents and standardizing the quality of yak yogurt.