Characterization of autochthonous lactic acid bacteria from an artisanal Italian cheese | Karakterizacija mlečnokislinskih bakterij v avtohtonem kmečkem italijanskem siru

anglais. We studied the natural lactic bacteria population of an artisanal Italian cheese, Toma piemontese POD, from Piedmont (Northwest Italy), in order to select new strains to be used as starters in large-scale production. Isolates collected from curd and ripened artisanal cheeses were identified by the combined use of PCR 16S-23S rDNA spacer analysis, species-specific probes and 16S rDNA sequencing. Lactococci constitued 67% of the coccal isolates. Enterococci were also isolated together with strains of Streptococcus macedonicus and S. thermophilus. Lactobacilli were only detected in three samples of curds. Acidification and proteolytic activity and aroma production were also determined for each isolate. On the basis of the results a few isolates were selected and used as starters in cheesemaking trials with both raw and pasteurised milk. The produced cheeses were sensory evaluated and two of them showed typical Toma piemontese taste and flavour. The results suggest the possibility to use these new starters in both dairy industry and artisanal cheesemaking to improve product quality.

slovène. Preučevali smo naravne populacije mlečnokislinskih bakterij v avtohtonem kmečkem italijanskem siru “Toma piemontese POD” iz Piemonta v severozahodni Italiji, da bi pridobili nove seve, ki bi jih lahko uporabljali v industrijski proizvodnji. Izolate, ki smo jih osamili iz sirnine in zrelega avtohtonega sira smo identificirali s pomočjo kombinirane uporabe različnih metod in sicer analizo vmesne regije 16S-23S rDNA z verižno reakcijo s polimerazo, uporabo vrstno specifičnih začetnikov in sekvenciranjem 16S rDNA. Lactococci so predstavljali 67 % vseh izoliranih kokov. Enterokoke smo izolirali skupaj s sevi vrst Streptococcus macedonicus in S. thermophilus. Laktobacile smo odkrili samo v treh vzorcih sirnine. Za vsak izolat smo ugotavljali tudi proteolitično aktivnost, acidifikacijsko sposobnost in proizvodnjo arome. Na osnovi rezultatov smo izbrali nekatere isolate in jih kot starterske kulture uporabili v poskusih izdelave sira in sicer iz surovega in pasteriziranega mleka. Sire smo senzorično ocenili in dva med njimi sta imela za “Toma piemontese» značilen okus in vonj. Naši rezultati nakazujejo možnost izboljšanja kakovosti proizvodov z uporabo teh novih starterskih kultur v sirarski industriji in v kmečki avtohtoni proizvodnji sirov.