Influence of Cheese Composition on Aroma Content, Release, and Perception.

The quality of a cheese is determined by the balance of aroma compounds primarily produced by microorganisms during the transformation of milk into ripened cheese. The microorganisms, along with the technological parameters used in cheese production, influence aroma formation. The perception of these compounds is further influenced by the composition and structure of the cheese. This study aimed to characterize how cheese composition affects aroma compound production, release, and perception. Sixteen cheeses were produced under controlled conditions, followed by a quantitative descriptive analysis post ripening. Aroma composition was analyzed using HS-SPME-GC-MS, and a dynamic sensory evaluation (TCATA) was combined with nosespace analysis using PTR-ToF-MS. Image analysis was also conducted to characterize cheese structure. Cheese fat and whey lactose contents were identified as key factors in the variability of sensory attributes. GC-MS analyses identified 27 compounds correlated with sensory attributes. In terms of aroma compound release, 23 ions were monitored, with fat, salt, and lactose levels significantly affecting the release of most compounds. Therefore, cheese fat, salt, and whey lactose levels, as well as the types of microbial strains, play a role in influencing the composition, structure, release of aroma compounds, and sensory perception.

Microbial composition and viability of natural whey starters used in PDO Comté cheese-making.

Natural whey starters (NWS) are cultures with undefined multiple-strains species commonly used to speed up the fermentation process of cheeses. The aim of this study was to explore the diversity and the viability of Comté cheese NWS microbiota. Culture-dependent methods, i.e. plate counting and genotypic characterization, and culture-independent methods, i.e. qPCR, viability-qPCR, fluorescence microscopy and DNA metabarcoding, were combined to analyze thirty-six NWS collected in six Comté cheese factories at two seasons. Our results highlighted that NWS were dominated by Streptococcus thermophilus (ST) and thermophilic lactobacilli. These species showed a diversity of strains based on Rep-PCR. The dominance of Lactobacillus helveticus (LH) over Lactobacillus delbrueckii (LD) varied depending on the factory and the season. This highlighted two types of NWS: the type-ST/LD (LD > LH) and the type-ST/LH (LD < LH). The microbial composition varied depending on cheese factory. One factory was distinguished by its level of culturable microbial groups (ST, enterococci and yeast) and its fungi diversity. The approaches used to estimate the viability showed that most NWS cells were viable. Further investigations are needed to understand the microbial diversity of these NWS.