Tracking casein phosphopeptides during fermentation by high performance liquid chromatography-tandem mass spectrometry

Casein phosphopeptides (CPPs) are phosphorylated fragments of casein, which have a variety of biological functions such as promotion of mineral absorption, antioxidation and prevention of dental caries. This study investigated CPPs in milk and yogurt fermented by Lb. bulgaricus (Lactobacillus debrueckii subsp. bulgaricus) and S. thermophilus (Streptococcus thermophilus) with high performance liquid chromatography-tandem mass spectrometry. The results showed that milk contained endogenous CPPs, which were mainly derived from high abundance of caseins αs1-CN and β-CN, in the role of endogenous protease. After milk fermented with Lb. bulgaricus and S. thermophilus, more CPPs and phosphorylation sites were released in the action of lactic acid bacteria proteases. The CPPs with the character of SpSpSpEE were identified in yogurt. The structure of caseins played an important role in CPPs releasing in the process of fermentation. In conclusion, fermentation by lactic acid bacteria is helpful to release CPPs containing SpSpSpEE, which can promote mineral absorption.