Mesopic fermentation contributes more to the formation of important flavor compounds and increased growth of Lactobacillus casei Zhang than does high temperature during milk fermentation and storage.

Probiotic fermented milk is more and more popular due to their positive health associated properties. However, fermentation temperature and other process conditions may affect the growth and metabolism of probiotic strains, thereby affecting quality of the final products. In this study, the growth behaviors and metabolomic profiles of yogurts induced by Lactobacillus casei Zhang at fermentation termination (FT) and d 10 of storage (S10d) under different fermentation temperatures at 37°C (low) and 42°C (high) were analyzed and compared using liquid chromatography-mass spectrometry (MS)- and gas chromatography-MS-based metabolomics approaches. At 37°C, the growth of L. casei Zhang at FT and S10d was significantly increased, and the potential relationship between riboflavin, starch, and sucrose metabolism and growth of L. casei Zhang may be mutually promoting. Fermentation temperature (37°C and 42°C) affected volatile and nonvolatile metabolomic profiles and pathways. The levels of acetaldehyde, 2,3-butanedione, acetoin, butyric acid, decanoic acid, hexanoic acid, and octanoic acid were significantly higher at 37°C than at 42°C at FT and S10d. This indicates that the low temperature (37°C) most likely contributes more to the formation of important flavor compounds during the fermentation process and production of short-chain fatty acids during storage.