Propionibacterium freudenreichii strains quantitatively affect production of volatile compounds in Swiss cheese

Abstract

-Cheese flavour is the result of a complex mixture of volatile compounds, originating mainly from the enzymatic degradation of curd components by cheese microflora during cheese ripening. Directing cheese flavour development requires knowledge on inter-and intra-species contributions to flavour development, i.e. identification of the volatile (flavour) compounds produced by each strain. The aim of this study was to identify the volatile compounds produced in Swiss cheese by Propionibacterium freudenreichii, one of the species essential for the development of the characteristic flavour of this type of cheese. The volatile profile of compounds obtained from smallscale (1/100) Swiss cheeses, with or without P. freudenreichii, were compared (three strains tested, in association with three thermophilic lactic starters, i.e. twelve cheeses, manufactured in duplicate). Neutral volatile compounds, extracted by dynamic headspace, and free fatty acids were identified using gas chromatography-mass spectrometry. The concentrations of all carboxylic acids and 14 of 58 neutral compounds were significantly higher in the presence of propionibacteria (PAB). The three PAB strains tested produced the same volatile compounds, but observed quantitative differences were strain-dependent. Propionic acid and four propionate esters were detected only in the presence of PAB. Moreover, cheeses with PAB contained two-to three-fold higher levels of free fatty acids derived from lipolysis and five-to fifty-fold higher levels of branched-chain compounds derived from isoleucine catabolism (2-methylbutanal, 2-methylbutanol and 2-methylbutanoic acid) and from leucine catabolism (3-methylbutanoic acid). Lactic starters induced significant variations in the concentrations of some of the compounds produced by PAB, such as methylbutanoic acids and free fatty acids, which varied by 2.0 and 1.4, respectively, as a function of the lactobacilli strains. PAB strains affect the concentration of varied volatile compounds and could therefore have distinct contributions to the formation of Swiss cheese flavour.

The role of propionibacteria in the volatile profile of Pategrás cheeses

“…In both types of cheeses, a steady decrease was recorded after 35 days, which was in accordance with the progressive increase of acetoin levels. Contrary to that observed in this study, a lower concentration of diacetyl in the presence of PAB (Thierry et al 2005b) and inconsistent variations during ripening (Thierry et al 1999) have been reported. With some exceptions, methyl ketones (C 3 to C 9 ) showed a moderate increase during ripening and the levels of some of them such as 2-propanone and 2-pentanone were always higher in cheeses R in comparison to cheeses E. Similarly, Thierry et al (1999) reported increased levels of methyl ketones throughout the ripening in Emmental cheeses.…”

“…However, this ability has been shown to be highly strain dependent. This would explain the fact that 3-methyl-1-butanol was found at significantly greater levels in some cheeses made with PAB (Thierry and Maillard 2002;Thierry et al 2005a), while in other cheeses, its concentration was not affected by the presence of these microorganisms (Thierry et al 2005b). …”

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

“…freudenreichii greatly contributes to Swiss-type cheese flavour by producing compounds from three main pathways: lactate and aspartate fermentation, amino acid catabolism, and fat hydrolysis [59]. As described above, the end-products of propionic fermentation are considered as flavour compounds in cheese whereas the co-metabolism of aspartate leads to additional CO2 production.…”

The Secreted Esterase of Propionibacterium freudenreichii Has a Major Role in Cheese Lipolysis

“…Specifically, ITGP18 was previously shown to exhibit low lipolytic activity, ITGP9 exhibited medium activity, and ITGP23 exhibited high activity in cheese, with net increases in FFA concentrations of 0.2, 2.1, and 3 to 4 mg/g cheese, respectively, compared to the control cheeses manufactured without propionibacteria (6,8). Under the in vitro conditions of the present study, these three strains released 0.137, 0.379, and 1.109 mg FFA/g culture medium, respectively.…”

“…The extent of lipolysis has been shown to vary significantly under the same cheesemaking conditions, depending on the strain used, with the amount of released FFA varying up to 3-fold (6)(7)(8)(9). In particular, some strains exhibit very low lipolytic activity (8).…”