A comparison for acid production, proteolysis, autolysis and inhibitory properties of lactic acid bacteria from fresh and mature Feta PDO Greek cheese, made at three different mountainous areas.

Isolates of NSLAB were obtained from fresh (58 isolates) and mature (38) Feta cheese made at household level in three different mountainous areas, in order to study the effect of the area of production on NSLAB composition and their technological characteristics. Results obtained by SDS-PAGE of whole-cell proteins indicated that the microflora of the fresh cheese was composed of either lactococci (areas 1, 2), or lactococci and enterococci (area 3). The NSLAB microflora of mature cheese was composed almost entirely of lactobacilli species, differing according to the area of production. Species allocation by the SDS-PAGE method was confirmed by sequencing representative strains. Lactococci of cheese made in area 1 exhibited a narrow spectrum of antibacterial activity compared to isolates from areas 2 and 3, while for lactobacilli from all three areas a similar spectrum was noticed. Lactococci from area 2 exhibited higher (P<0.05) mean acidifying activity than lactococci from area 1. The isolates from the three areas also differed in respect of their caseinolytic activity, with preferences towards ß-CN (areas 1 and 2) or αs-CN (area 3). Mean proteolytic activity of lactococci from area 1 was stronger (P<0.05) than that of lactococci from area 2 and the same was observed for their mean aminopeptidase activity, as well as their extent of autolysis at pH5.1. Mean acidifying activity of lactobacilli after 6h was for strains of area 3>2=1. The strains from areas 1 and 3 degraded preferentially αs-CN, while a clear preference towards ß-CN was noticed for strains of area 2; their mean proteolytic activity was for strains of area 1 higher (P<0.05) than strains from area 3. The above results suggest that cheeses from the three areas differ in species composition of NSLAB and their technological properties. Principal component analysis of results on acidifying and proteolytic activities as well as autolysis allowed the distinction of lactococci according to their derivation area enabling the selection of appropriate strains as starters for cheese production in each area.

Differentiation of lactococci from 2 Greek cheeses with protected designation of origin by phenotypic criteria and RAPD-PCR.

Seventy-six lactococci isolates from 2 protected designation of origin (PDO) cheeses were studied for their acidification ability, proteolytic activity, and inhibitory activities as well as their intraspecies characterization by randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). Fifty-two of them were characterized as Lactococcus lactis subsp. lactis by the SDS-PAGE of whole-cell proteins. The test strains increased the amount of acid in milk from 6 to 24 h as well as the quantities of amino acids on incubation for 4 d. The majority of the isolates degraded preferentially αs-casein. The isolates from Feta differed from those of Graviera Kritis in respect of ß-casein degradation. This fragment was either not degraded or underwent a small degradation by lactococci from Feta. A stronger intensity of acidification for the isolates from Feta and a higher casein breakdown ability for those from Graviera Kritis were also recorded. Lactococci from Feta and Graviera Kritis inhibited, preferentially, the growth of Escherichia coli O157:H7, and Yersinia enterocolitica, respectively. A high heterogeneity among the isolates according to RAPD-PCR was determined, as well as grouping of the isolates according to their source of isolation. Selected isolates from each cheese could be used as starters to make either Feta or Graviera Kritis.