Formation of volatile compounds, peptidolysis and carbohydrate fermentation by mesophilic lactobacilli and streptoccocci cultures in a cheese extract

Abstract

Many studies about the influence of Lactococcus lactis on cheese flavour have been reported, while the impact of mesophilic lactobacilli and Streptococcus thermophilus, either as single or mixed cultures, have been less studied. The ability of Lactobacillus paracasei 90, Lb. casei 72 (INLAIN collection) and S. thermophilus 2 (commercial strain) to produce flavour-related biochemical changes, as single or mixed (lactobacilli + streptococci) cultures, was assessed in a cheese model. These three strains, with different activities of glutamate dehydrogenase (GDH) and aminotransferases (AT), were incubated (14d/37°C) alone or in mixed cultures in a cheese model consisting of a sterile extract of a fresh cheese. Mesophilic lactobacilli showed fermentation of carbohydrates, an increase of peptidolysis and production of volatile compounds that were correlated with their AT activities. In addition, these strains also produced completely different profiles of the amino acceptor compounds: pyruvate and α-ketoglutarate. S. thermophilus 2 increased the level of α-ketoglutarate due to its high GDH activity, but its contribution to flavour compound production was negligible; small additional changes existed when S. thermophilus 2 was mixed with the lactobacilli. Biochemical changes leading to flavour formation were mainly due to the activity of lactobacilli. Our results suggest that the AT profile and the peptidolytic activity of each strain influenced the volatilome of the extracts during incubation. So, both lactobacilli strains could be used as adjunct cultures in cheeses to increase/ diversify the flavour, but more studies are needed to deepen the knowledge about the potential of S. thermophilus 2 for the production of flavour compounds.

Characterization of Volatile Compounds by SPME‐GC‐MS During the Ripening of Kedong Sufu, a Typical Chinese Traditional Bacteria‐Fermented Soybean Product

“…At the beginning of sufu fermentation, microorganism metabolism tended to be vigorous, leading to high lipolysis and proteolysis. However, the total content of acids was significantly reduced during postfermentation, probably as they transformed into other compounds, such as esters (Peralta, Wolf, Perotti, Bergamini, & Hynes, ).…”

Influence of the culture preparation and the addition of an adjunct culture on the ripening profiles of hard cheese

“…3-hydroxy butan-2-one is an important aroma compound in grana cheeses, which can be produced by the action of mesophilic bacteria (Fox et al 2000). Peralta et al (2016) demonstrated the ability of Lp90 to produce this compound in a hard cheese extract. In addition, Wa and Ma cheeses had higher levels of acetic acid; a similar effect of Lp90 was previously observed in Cremoso cheese and in a soft cheese extract (Milesi et al 2010; Peralta et al 2016).…”

“…Peralta et al (2016) demonstrated the ability of Lp90 to produce this compound in a hard cheese extract. In addition, Wa and Ma cheeses had higher levels of acetic acid; a similar effect of Lp90 was previously observed in Cremoso cheese and in a soft cheese extract (Milesi et al 2010; Peralta et al 2016). Lp90 strain showed a tendency to metabolize 2-methyl-propan-1-ol, 2-methylpropanoic and 3-methylbutanoic acids as their area values were lower in cheeses added with Lp90; this effect depended on the growth medium used for the culture preparation.…”

Evaluation of the Potential of Lactobacillus paracasei Adjuncts for Flavor Compounds Development and Diversification in Short-Aged Cheddar Cheese

“…A direct correlation between the concentration of FAA and cheese flavor cannot be established, since different types of cheeses have similar relative proportions of amino acids, but differ distinctly in flavor (Sousa et al, 2001 ). In addition, as metabolism of amino acids seems to be strain-specific, a similar pool of FAA will be converted to different volatiles by different strains (Peralta et al, 2016 ). In this study, a limited differentiation of cheeses was observed based on FAA levels.…”