Objectives The dominant species present in the whey starter of PDO and traditional cheeses play a key role, positive or negative, in defining the specific organoleptic characteristics of each cheese. This study provides a view of the composition of the yeast community in natural whey starter for Trentingrana PDO and Provolone Valpadana PDO production. The yeasts isolated from the whey cultures of these two dairy products have been identified, typed and characterized by phenotypic and genotypic methods in order to highlight their biodiversity and metabolic potential. In particular, the strains were evaluated based on some features of technological interest (lipolysis, proteolysis and ability to form biofilms). Methods Thirty-three natural whey starters (21 from 13 Trentingrana DOP dairies and 12 from one Provolone Valpadana DOP dairy) were analyzed for yeast count. The 54 isolates (48 from Trentingrana and 6 from Provolone) were typed by RAPD-PCR and the different biotypes identified by sequencing the D1/D2 domain of the large subunit RNA gene and the internal transcribed spacer regions of the rDNA. They were also technologically characterized (lipolytic activity, proteolytic activity and biofilm production) according to methods reported in the literature. Results The yeast content in whey starters varied between 0.95 and 5.27 log10 UFC/mL, and, in particular, a high variability between samples from processing in Trentingrana DOP was highlighted. The isolates showed good inter- and intra-specific variability and the biotypes identified were found to belong to 9 genera and 15 species, markedly divided according to cheese origin. Almost all strains were lipolytic, while 30% showed proteolytic activity. A marked lipo- and proteolytic potential by Aureobasidium pullulans emerged. Most strains were also able to form biofilm, albeit weakly or moderately. Conclusion The whey starter of Italian PDO cheeses is characterized by a rich biodiversity in terms of yeast species, possessing a metabolic potential that can strongly influence the quality and safety of dairy products.
Obiettivi Le specie dominanti presenti nel siero-innesto di produzioni casearie DOP e tradizionali giocano un ruolo chiave, in termini positivi o negativi, nella definizione delle caratteristiche organolettiche peculiari di ciascun formaggioIl presente studio ha indagato la presenza di lieviti e nel siero-innesto naturale di Trentingrana DOP e Provolone Valpadana DOP. I lieviti isolati dal siero-innesto di questi due prodotti caseari sono stati identificati, tipizzati e caratterizzati attraverso metodi fenotipici e genotipici per evidenziarne la biodiversità e il potenziale metabolico. In particolare, i ceppi sono stati analizzati in relazione ad alcune caratteristiche di interesse tecnologico. Materiali e metodi Trentatré campioni di siero-innesto (21 dalla lavorazione a Trentingrana DOP di 13 caseifici dislocati in Trentino-Alto Adige e 12 dalla lavorazione a Provolone Valpadana DOP di un unico produttore) sono stati sottoposti alla ricerca di lieviti. I 54 (48 per Trentingrana e 6 per Provolone) isolati sono stati tipizzati mediante RAPD-PCR e i differenti biotipi identificati tramite sequenziamento della regione ITS e della regione D1/D2 contenuta nel gene 26S dell' rDNA . Si è, quindi, proceduto alla valutazione di alcune caratteristiche di interesse tecnologico (attività lipolitica, proteolitica e produzione di biofilm) secondo metodiche riportate in letteratura. Risultati Le analisi microbiologiche hanno evidenziato nei sieri-innesto un contenuto di lieviti compreso tra 0.95 e 5.27 log10 UFC/mL, e, in particolare, un'elevata variabilità tra i campioni provenienti da lavorazione a Trentingrana DOP. Gli isolati presentavano buona variabilità inter- e intra-specifica e i biotipi individuati sono risultati appartenere a 9 generi e 15 specie diverse, marcatamente suddivisi in funzione della provenienza casearia. La quasi totalità dei ceppi è risultata lipolitica, mentre il 30% ha mostrato attività proteolitica. Un marcato potere lipo- e proteolitico è emerso per la specie Aureobasidium pullulans. La maggior parte dei ceppi si è dimostrata anche in grado di formare biofilm, anche se in maniera debole o moderata. Conclusioni Il siero-innesto di produzioni casearie italiane DOP è caratterizzato da una ricca biodiversità in termini di specie di lieviti, che possiedono un potenziale metabolico in grado di influenzare fortemente la qualità e la sicurezza dei prodotti caseari.
Biodiversità di lieviti isolati da siero-innesto di produzioni casearie italiane
Morandi S;Silvetti T;Brasca M
2019
Abstract
Objectives The dominant species present in the whey starter of PDO and traditional cheeses play a key role, positive or negative, in defining the specific organoleptic characteristics of each cheese. This study provides a view of the composition of the yeast community in natural whey starter for Trentingrana PDO and Provolone Valpadana PDO production. The yeasts isolated from the whey cultures of these two dairy products have been identified, typed and characterized by phenotypic and genotypic methods in order to highlight their biodiversity and metabolic potential. In particular, the strains were evaluated based on some features of technological interest (lipolysis, proteolysis and ability to form biofilms). Methods Thirty-three natural whey starters (21 from 13 Trentingrana DOP dairies and 12 from one Provolone Valpadana DOP dairy) were analyzed for yeast count. The 54 isolates (48 from Trentingrana and 6 from Provolone) were typed by RAPD-PCR and the different biotypes identified by sequencing the D1/D2 domain of the large subunit RNA gene and the internal transcribed spacer regions of the rDNA. They were also technologically characterized (lipolytic activity, proteolytic activity and biofilm production) according to methods reported in the literature. Results The yeast content in whey starters varied between 0.95 and 5.27 log10 UFC/mL, and, in particular, a high variability between samples from processing in Trentingrana DOP was highlighted. The isolates showed good inter- and intra-specific variability and the biotypes identified were found to belong to 9 genera and 15 species, markedly divided according to cheese origin. Almost all strains were lipolytic, while 30% showed proteolytic activity. A marked lipo- and proteolytic potential by Aureobasidium pullulans emerged. Most strains were also able to form biofilm, albeit weakly or moderately. Conclusion The whey starter of Italian PDO cheeses is characterized by a rich biodiversity in terms of yeast species, possessing a metabolic potential that can strongly influence the quality and safety of dairy products.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
