Relationship between the Dynamics of Gross Composition, Free Fatty Acids and Biogenic Amines, and Microbial Shifts during the Ripening of Raw Ewe Milk-Derived Idiazabal Cheese

Simple Summary The microbiota present in cheese is of special interest as it contributes to the synthesis of different compounds related to cheese quality and safety. However, to date, no studies have been carried out in cheese to elucidate the relationship between bacterial communities, characterized by high-throughput sequencing (HTS), and the dynamics of gross composition, free fatty acids (FFAs) and biogenic amines (BAs) during ripening. In this sense, this work focused on Idiazabal PDO cheese, a semi-hard or hard cheese produced from raw ewe milk. Results revealed that the non-starter lactic acid bacteria Lactobacillus, Enterococcus and Streptococcus were positively associated with the changes in gross composition and the release of FFAs, while only Lactobacillus was positively associated with the production of BAs. Several genera of environmental or undesirable bacteria presented negative correlations, which could indicate a negative impact of gross composition on their growth, the antimicrobial effect of FFAs and/or the importance of such FFAs as metabolic substrates for these bacteria, and their capability to degrade BAs. This study reports for the first time the relationship between bacterial succession, characterized by high-throughput sequencing (sequencing of V3-V4 16S rRNA regions), and the evolution of gross composition, free fatty acids (FFAs) and biogenic amines (BAs) during cheese ripening. Specifically, Idiazabal PDO cheese, a raw ewe milk-derived semi-hard o hard cheese, was analysed. Altogether, 8 gross parameters were monitored (pH, dry matter, protein, fat, Ca, Mg, P and NaCl) and 21 FFAs and 8 BAs were detected. The ripening time influenced the concentration of most physico-chemical parameters, whereas the producer mainly affected the gross composition and FFAs. Through an O2PLS approach, the non-starter lactic acid bacteria Lactobacillus, Enterococcus and Streptococcus were reported as positively related to the evolution of gross composition and FFAs release, while only Lactobacillus was positively related to BAs production. Several environmental or non-desirable bacteria showed negative correlations, which could indicate the negative impact of gross composition on their growth, the antimicrobial effect of FFAs and/or the metabolic use of FFAs by these genera, and their ability to degrade BAs. Nonetheless, Obesumbacterium and Chromohalobacter were positively associated with the synthesis of FFAs and BAs, respectively. This research work provides novel information that may contribute to the understanding of possible functional relationships between bacterial communities and the evolution of several cheese quality and safety parameters.

Automated summary

This study investigates the relationship between bacterial communities and the evolution of gross composition, free fatty acids (FFAs), and biogenic amines (BAs) during cheese ripening. The results show that non-starter lactic acid bacteria Lactobacillus, Enterococcus, and Streptococcus are positively associated with changes in gross composition and the release of FFAs, while only Lactobacillus is positively associated with the production of BAs. Several undesirable bacteria are negatively correlated, indicating a potential negative impact of gross composition on their growth and the antimicrobial effect of FFAs. Obesumbacterium and Chromohalobacter are positively associated with the synthesis of FFAs and BAs, respectively. This research provides valuable information on the relationship between bacterial communities and cheese quality and safety parameters.