Propionibacteria and facultatively heterofermentative lactobacilli weakly contribute to secondary proteolysis of Emmental cheese

Abstract

-Proteolysis is a major event during cheese ripening. In Emmental cheese, the contribution of plasmin and thermophilic lactic starters to proteolysis has been well established. Our aim was to assess the contribution of each ripening flora to secondary proteolysis. With this aim, we used the aqueous phase (or juice) of Emmental cheese as a culture medium, which contains the enzymes released by thermophilic starters. Crude juice (containing all cheese flora) and cell-free juice either inoculated with two propionibacteria (PAB) strains or uninoculated (control), were incubated under anaerobiosis at 24 o C for 20 d. Free amino groups and free amino acids, bacterial growth and organic acids were followed throughout the incubation time. Facultatively heterofermentative lactobacilli (FHL) represented the main flora growing in crude juice up to 10 d incubation. FHL and PAB respectively reached 4.0 × 10 8 and 1.0 × 10 10 cfu . mL -1 of juice and consumed citrate and lactate, in accordance with that already observed in cheese. The level of amino groups increased linearly during incubation time by a factor of 1.9 in crude juice, 1.7 in cell-free juice and only 1.5 in juice inoculated with PAB strains, showing that the enzymes of thermophilic starters are the main contributors to secondary proteolysis. FHL growth resulted in a 16% increase in free amino acids compared to cell-free juice and in exhaustion of Arg and His. Both PAB strains caused a 18-27% decrease in free amino acids and also modified the amino acid distribution, with consumption of Asp, Gly, Glu, Ser and Ile. secondary proteolysis / Propionibacterium / facultative heterofermentative lactobacilli / Emmental cheese / free amino acid Résumé -Les lactobacilles hétérofermentaires facultatifs et les bactéries propioniques ont une faible contribution à la protéolyse secondaire de l'Emmental. La protéolyse est un phéno-mène majeur dans l'affinage du fromage. Dans l'Emmental, la contribution de la plasmine et des levains thermophiles à la protéolyse secondaire a été bien établie. Le but de cette étude était de 339 * Correspondence and reprints

Dairy Propionibacteria: Less Conventional Probiotics to Improve the Human and Animal Health

“…In contrast, although it possesses diverse intracellular peptidases, P. freudenreichii has a limited role in secondary proteolysis, compared to starter and non-starter lactic acid bacteria (NSLAB), because it does not lyse in cheese [66].…”

Use of DNA Quantification To Measure Growth and Autolysis of Lactococcus and Propionibacterium spp. in Mixed Populations

“…Langsrud et al (21,22) observed a correlation between autolysis of propionibacteria in milk and production of free proline, and Østlie et al (31) confirmed this correlation for broth media. Gagnaire et al (13) showed that strains of P. freudenreichii did not contribute to proteolysis in an aqueous phase in Emmental cheese and that propionibacteria were not significantly involved in the production of proline. Few peptidases from P. freudenreichii were also found in Emmental cheese by a proteomic approach (12).…”

Split defect and secondary fermentation in Swiss-type cheeses – A review

“…The NSLAB in Swiss-type cheese are mainly composed of FHL that begin growth at the beginning of ripening [35] and eventually reach~10 8 cfu·g −1 [109]. In a study by Demarigny et al [21], L. paracasei, L. plantarum, L. rhamnosus and L. brevis were all detected in Swiss-type cheese, but as the cheese ripened L. paracasei began to dominate the NSLAB flora.…”

“…Berdagué et al [6] and Grappin et al [43] related split intensity to higher levels of secondary proteolysis as measured nitrogen levels soluble in phosphotungstic acid. In Swiss-type cheese, plasmin and the proteinases and peptidases from starter, non-starter and secondary starter [34,35] are the principal proteolytic agents [25,93]. The activity of proteolytic enzymes in cheese is influenced by a w , copper content, water content, lactic acid concentration, pH, storage temperature and time [105].…”

“…Lactobacillus helveticus is recognised as possessing efficient protease and peptidase activities with respect to milk proteins [26,73]. L. helveticus autolyses rapidly during ripening and releases active peptidases in the cheese [35,113], and increases in the levels of amino acids and peptides in whey and most amino acids produced were shown to be utilised by the PAB [85]. Strains of L. helveticus used for cheese manufacture have been shown to have an influence on secondary fermentation [30].…”