Maturing dynamics of surface microflora in Fontina PDO cheese studied by culture-dependent and -independent methods

Abstract

To study the evolution of rind microbial communities in Fontina PDO cheese. Four batches were examined for their surface microflora during ripening, carried out in two different maturing caves, at Ollomont and Pré-Saint-Didier, Aosta Valley region, Northwest of Italy. Culture-dependent methodologies were combined with culture-independent analysis (PCR-DGGE). Yeasts were found to increase from 10(3) to 10(6) CFU cm(-2) in 28 days, with consequent rise of surface pH, which allowed the growth of salt-tolerant bacteria, in particular coryneforms which reached 10(9) CFU cm(-2) at the end of 3 months. Coagulase-negative cocci and lactic acid bacteria reached 10(7) CFU cm(-2) in the same period. Debaryomyces hansenii and Candida sake were the species more constantly present throughout the whole maturing process. As early as after 1 day since manufacture, Lactococcus lactis subsp. lactis and Streptococcus thermophilus were detected on cheese rinds. Arthrobacter nicotianae, Brevibacterium casei and Corynebacterium glutamicum were found after 7-28 days. According to cluster analysis of DGGE profiles, the maturing environment seemed to influence the dynamics of microbial groups on Fontina surfaces. These results represent a first picture of micro-organisms colonizing Fontina PDO rinds. Further studies are in progress to better understand the origin of this surface microflora and to formulate surface starters.