Flavor profiles and genetic basis differences of Lacticaseibacillus paracasei isolates from different isolations in fermented milk.

Lacticaseibacillus paracasei from diverse traditional fermented foods exhibit unique flavor profiles in dairy products. In this study, 101 Lacticaseibacillus isolates were categorized into four distinct classes, with those originating from fermented dairy products demonstrating the highest flavor diversity. Multivariate statistical analyses identified diacetyl, acetoin, and 2-nonanone as key volatile compounds characterizing ketone-type isolates. Further examination of two ketone-type isolates and one non-ketone-type isolate, isolated from kurut, sour porridge, and Huangjiu mash respectively, revealed their specific abilities to produce ketones, lactones, and alcohols. Genome comparison of ketone-type and non-ketone-type L. paracasei isolates revealed disparities in the cit gene cluster, als, and but genes within the citrate metabolic pathway. These findings provide novel insights into the flavor diversity and help identify potential key genes involved in flavor formation in L. paracasei isolates, thereby facilitating the application of L. paracasei isolates in fermented dairy products.