BMMIB-BEHIND MICROBE-MICROBE INTRACTIONS IN BLUE CHEESE

Gorgonzola is a blue-veined, mould-ripened cheese, made from pasteurized cow’s milk inoculated with starter cultures (Streptococcus thermophilus and Lactobacillus delbrueckii), along with Saccharomyces cerevisiae and Penicillium roqueforti, the main responsible of the aroma and flavour of the cheese at the end of ripening. For this reason, monitoring the fungal growth and unravel the microbial dynamics during the ripening process is crucial. Traditional methods based on colony forming unit (CFU) along with alternatives (ergosterol, dry weight, spores counting) are not suitable for hyphal filaments quantification in the cheese matrix. Here we monitored and compared the P. roqueforti development between two Gorgonzola productions from two different years and the same plant, by means of a qPCR assay, mass spectrometry-based chemical analysis and an assay with a glutamate-sensitive luminescent biosensor for the evaluation of proteolysis. qPCR assay was based on a species-specific primer set targeted on ari1 gene. This assay allowed the monitoring of P. roqueforti development during cheese ripening. The lipolysis and proteolysis cheese profiles obtained by mass-spectrometry and luminometric analysis were in good agreement with the qPCR data, revealing that the most relevant blooming of the mould occurs after 20 days of ripening, and that the most recent production had a lower amount of fungal mycelium produced and a lower enzymatic activity, thus affecting the final product quality. The metabolic analysis on sugars consumption revealed the importance of galactose degradation on the final product quality. The analytical methods here described are useful for a rapid evaluation of the maturation process and the quality of blue-cheeses.