Higher microbial diversity in raw than in pasteurized milk Raclette-type cheese enhances peptide and metabolite diversity after in vitro digestion

Abstract

Numerous bacteria are responsible for hydrolysis of proteins during cheese ripening. The raw milk flora is a major source of bacterial variety, starter cultures are needed for successful acidification of the cheese and proteolytic strains like Lactobacillus helveticus, are added for flavor improvement or acceleration of ripening processes. To study the impact of higher bacterial diversity in cheese on protein hydrolysis during simulated human digestion, Raclette-type cheeses were produced from raw or heat treated milk, with or without proteolytic L. helveticus and ripened for 120 days. Kinetic processes were studied with a dynamic (DIDGI®) in vitro protocol and endpoints with the static INFOGEST in vitro digestion protocol, allowing a comparison of the two in vitro protocols at the level of gastric and intestinal endpoints. Both digestion protocols resulted in comparable peptide patterns after intestinal digestion and higher microbial diversity in cheeses led to a more diverse peptidome after simulated digestion.

Keywords: Bacterial diversity; Bioactive peptides; Cheese proteins; Dynamic and static in vitro digestion; Free amino acids; L. helveticus; Mass spectrometry; Protein hydrolysis.