Microbial population profile during ripening of Protected Designation of Origin (PDO) Silter cheese, produced with and without autochthonous starter culture

Abstract

An autochthonous starter culture was used in the production of Protected Designation of Origin (PDO) Silter raw milk cheese, and compared to a control cheese in order to study its influence on microbial population dynamics during ripening. Curd and cheese at different ripening periods (0, 30, 60 and 200 days) from two independent dairies were analysed combining culture-based microbiological analysis, Length Heterogeneity-PCR and 16S microbiome profiling.The autochthonous starter determined higher lactic acid bacteria (LAB) levels for the first 30 days of ripening, without interfering with secondary microbiota that determines the tipicality of this cheese. Only a few genera and species persisted in the cheese despite the microbial richness of the curd. In addition, the high levels of different LAB reduced harmful microorganisms. The various analytic methods used resulted in discrepancies in the proportions of Enterococcus, Lactococcus and Lactobacillus spp., but the pivotal role of Streptococcus and Lactococcus genera was evident. The dominant species included those selected to formulate the starter (St. thermophilus, Lc. lactis, Ln. mesenteroides) as well as Lb. paracasei.The addition of autochthonous starter proved to be effective in controlling the first phases of the cheese-making, without compromising cheese typicality.