Strong effect ofPenicillium roquefortipopulations on volatile and metabolic compounds responsible for aromas, flavor and texture in blue cheeses

Abstract

The study of food microorganism domestication can bring important insights on adaptation mechanisms and have industrial applications. The Penicillium roqueforti mold is divided into four main populations, with two populations domesticated for blue-cheese making and two populations thriving in other environments. While most blue cheeses worldwide are made with the same P. roqueforti clonal lineage, the emblematic Roquefort cheeses are inoculated with a specific population. To study the differences among P.roqueforti populations in the context of domestication for cheesemaking, we compared blue cheeses made with the four fungal populations following Roquefort-type production specifications. We found that the P. roqueforti populations had a minor impact on the cheese bacterial diversity and none on the main microorganism abundance. The cheese P. roqueforti populations produced cheeses with higher percentages of blue area and with different sets and higher quantities of desired volatile compounds. The Roquefort P. roqueforti population in particular produced higher quantities of positive aromatic compounds in cheeses, which was related due to its most efficient proteolysis and lipolysis, and also produced cheeses with lower water activity, thus restricting spoiler microorganisms. Our results show the strong influence of P. roqueforti populations on several important aspects of cheese safety, appearance and flavour. The typical appearance and flavours of blue cheeses are therefore the result of human selection on P. roqueforti, thus constituting domestication, and the two cheese populations have acquired specificities. This has important implications for our understanding of adaptation and domestication processes as well as for improving cheese production.Importance: Several fungi have been domesticated for food fermentation, with selection for traits beneficial for food production. The mold used for making blue cheeses, Penicillium roqueforti, is subdivided into four genetically different populations, two being found in cheese, one being specific of the Roquefort protected designation of origin, and two in other environments. The cheese P. roqueforti populations produced bluer cheeses with higher quantities of desired volatile compounds. The Roquefort P. roqueforti population in particular produced higher quantities of positive aromatic compounds in cheeses, in relation to its most efficient proteolysis and lipolysis, and also produced cheeses with lower water activity, thus restricting spoiler microorganisms. Our results support that the blue cheese typical aspect and flavors are the result of a selection by humans and show the strong influence of P. roqueforti populations for several important aspects of cheese safety, aspect and flavor, paving the way for improving cheese production.

La domestication des champignons Penicillium du fromage

“…The P. roqueforti populations had a minor impact on the cheese bacterial diversity and none on Figure 3. Main findings from a recent study [75], in which analyses of experimental cheeses made following the Roquefort mode of production (e) and by inoculating strains from the four Penicillium roqueforti populations (a) showed beneficial traits in the two cheese populations, producing a higher blue surface on cheese slices (b), stronger lipolysis and proteolysis in caseo, and especially the Roquefort population (while the non-Roquefort population was found to have the highest lipolysis rate in vitro [70]), (c) and higher quantities of positive aromas (such as methyl ketones, with for example shown in d the 2pentanone and the 2-heptanone, and secondary alcohols, with for example shown in d the 2-heptanol and the 2-nonanol, with alcohol quantities multiplied by four compared to methyl ketones to be visible on the same axis).…”

“…Une étude récente a examiné les différences entre les populations de P. roqueforti dans le contexte de la domestication pour la fabrication de fromage en comparant les fromages bleus fabriqués avec les quatre populations fongiques suivant des conditions aussi proches que possible des spécifications de production commerciale de type Roquefort [75] ( Figure 3). Les populations de P. roqueforti ont eu un impact mineur sur la diversité bactérienne des fromages et aucun sur l'abondance des principaux microorganismes.…”

“…La population Roquefort de P. roqueforti en particulier a produit des composés aromatiques plus variés et en plus grande quantité, ce qui a donné des notes plus fruitées et plus fromagères aux fromages ; la production de ces composés étaient principalement à sa lipolyse et sa protéolyse les plus efficaces in caseo. Il est frappant de constater que la lipolyse et la protéolyse étaient effectivement les plus efficaces dans les fromages pour la population de P. roqueforti de Roquefort [75], tandis que la lipolyse était en revanche la plus efficace in vitro pour la population de P. roqueforti non Roquefort [70], ce qui montre l'importance des études in caseo. La population de Roquefort produit également des fromages à faible activité de l'eau, ce qui peut prévenir l'apparition de micro-organismes contaminants.…”

“…La population de Roquefort produit également des fromages à faible activité de l'eau, ce qui peut prévenir l'apparition de micro-organismes contaminants. Il y avait donc une forte influence des populations de P. roqueforti sur plusieurs aspects importants de la sécurité, de l'apparence et de la saveur du fromage [75].…”

“…A recent study investigated the differences among P. roqueforti populations in the context of domestication for cheesemaking by comparing blue cheeses made with the four fungal populations following conditions as close as possible to commercial production Roquefort-type production specifications [75] ( Figure 3). The P. roqueforti populations had a minor impact on the cheese bacterial diversity and none on Figure 3.…”