Microbiological characteristics of Parmigiano Reggiano cheese during the cheesemaking and the first months of the ripening

The aim of this work was to gain a comprehensive view of the microbiological characteristics of milk, natural whey starter, and cheese during the first months of ageing of Parmigiano Reggiano. A significant presence of different microbial groups in raw milk from the initial moments of production was rapidly substituted by various lactic acid bacteria. Natural whey starter contained a large number of thermophilic lactic acid bacteria (Lactobacillus helveticus, L. delbrueckii ssp. lactis, L. delbrueckii ssp. bulgaricus) and some facultatively heterofermentative lactic acid bacteria belonging to L. rhamnosus. Thermophilic lactic acid bacteria disappeared within 30 d. Rod-shaped mesophilic facultatively heterofermentative lactic acid microflora, consisting of L. casei, L. paracasei ssp. paracasei, L. paracasei ssp. tolerans, L. rhamnosus and pediococci, progressively increased up to the fifth month of ageing. Results showed that thermophilic lactobacilli were derived from natural whey starter whereas Streptococcus thermophilus originated from raw milk. Further, natural whey starter was the source of L. rhamnosus which was present throughout the entire period of the cheese ageing. The other components of non-starter lactic acid microflora derived from raw milk. Caract?ristiques microbiologiques du fromage Parmigiano Reggiano dans la phase de fabrication et durant les premiers mois d'affinage. Cet article a pour objectif de fournir une description compl?te des caract?ristiques microbiologiques du lait, du lactos?rum et du fromage Parmigiano Reggiano dans les premiers mois d'affinage. La pr?sence significative de groupes microbiologiques diff?rents dans le lait d?s les premiers instants du processus de fabrication ?tait rapidement remplac?e par la microflore lactique thermophile. Les ?chantillons de lactos?rum naturel contenaient un grand nombre de bact?ries lactiques thermophiles (Lactobacillus helveticus, L. delbrueckii ssp. lactis, L. delbrueckii ssp. bulgaricus) et quelques bact?ries lactiques h?t?rofermentaires facultatives appartenant ? l'esp?ce L. rhamnosus. Les bact?ries lactiques thermophiles ont disparu en l'espace de presque 30 jours pendant que la microflore lactique m?sophile h?t?rofermentaire facultative en b?tonnets, compos?e de L. casei, L. paracasei ssp. paracasei, L. paracasei ssp. tolerans, L. rhamnosus et de p?diocoques, a augment? progressivement jusqu'au 5e mois d'affinage. Streptococcus thermophilus, la microflore lactique m?sophile h?t?rofermentaire facultative, except? L. rhamnosus, et les autres bact?ries que nous avons isol?es dans les fromages pendant la fabrication et les premiers mois d'affinage provenaient du lait cru.