Dynamics of peptides released from cow milk fermented by kefir microorganisms during fermentation and storage periods

This study investigates the changes in peptides released during the fermentation and storage of cow milk with a kefir culture using porous graphitized carbon-liquid chromatography-tandem mass spectrometry (PGC-MS/MS). A comprehensive inventory of 695 distinct milk peptides from 98 milk proteins was determined, with 523 characterized within 24 h of fermentation. The quantitative evaluation of released peptides throughout the kefir fermentation process unveiled noteworthy variations. A total of 50 discrete bioactive peptides with various biological functions were determined throughout the fermentation stages. After fermentation, we identified 26 bioactive peptides within the resulting beverage, maintaining their stability throughout storage. In addition, during the storage periods, three new bioactive peptides emerged. The composition of bioactive peptides underwent alterations during fermentation but remained relatively constant during storage. Our study sheds light on the proteolytic activity of potential enzymes released into the milk samples from kefir cultures, contributing to the beverage's evolution during storage.