Abstract: This research aimed to study the bacterial community, free amino acid and fatty acid composition in featured dry fermented dairy products from some major pastoral areas of China and to analyze the correlation between bacterial community and free amino acid and fatty acid composition. The V4–V5 region of the bacterial 16S rDNA gene from Suannai Geda from Xinjiang, Qula from Tibet, Naizhazi from Inner Mongolia and milk fan from Yunnan was sequenced by high-throughput sequencing. The contents of fatty acids and free amino acids in these dairy products were determined by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography (LC), respectively. Finally, the correlation of bacterial community with α diversity, fatty acids and free amino acids was evaluated by redundancy analysis (RDA). High-throughput sequencing results showed that a total of 2 421 338 reads were obtained from these dry fermented dairy samples, of which 1 871 524 were clean reads. The bacterial Chao1 and Shannon indexes in milk fan were significantly higher than those in the other three dairy products. The bacterial community compositions in the four dairy products were significantly different, but Firmicutes was dominant in all these products, among which the relative abundance of Firmicutes in Suannai Geda was the highest. The relative abundance of Proteobacteria in Qula was the highest. At the genus level, the bacterial community compositions in the four dairy products were dominated by Lactococcus or Lactobacillus. The contents of 16 fatty acids in milk fan were higher than those in the other three products. A total of 24 free amino acids were detected, among which Suannai Geda contained the largest number (24) of free amino acids, and the contents of most free amino acids in Suannai Geda were higher than those in the other three products. Redundancy analysis showed that alanine was correlated with Acetobacter, Lactobacillus and Streptococcus, and acetic acid and butyric acid were correlated with Acinetobacter. The results of this study may provide a theoretical basis for the industrial production of traditional dry fermented dairy products in different provinces.

Key words: dry fermented dairy products; bacterial community structure; fatty acids; free amino acids; bacterial diversity