Assessment of microbial diversity of the dominant microbiota in fresh and mature PDO Feta cheese made at three mountainous areas of Greece

The aim of the present study was to assess the dynamics and the diversity of dominant microbiota in fresh and mature traditional Feta cheese produced in three mountainous areas and for that purpose a combined approach of culture-independent examination with conventional genotypic typing of the predominant NSLAB microbiota were applied. The microbial communities were monitored by PCR-DGGE on seven fresh and nine mature Feta cheese samples made by three artisanal producers. DGGE profiles suggested variability in the microbial composition of cheeses within the production area and distinctive differences in band profile of NSLAB in cheeses between the areas. PCR-DGGE analysis showed that Lactococcus spp. were the most widespread bacteria, Streptococcus macedonicus was detected often and, among lactobacilli, Lactobacillus plantarum prevailed. The diversity of NSLAB isolates from fresh and mature cheeses was assessed by RAPD-PCR and PFGE. Typing data indicated intraspecies genetic heterogeneity and specificity to the production area. Our results point to the conclusion that the manufacturing environment influence the dynamic and the diversity of microbial groups developed in the cheese and possibly the cheese flavour. In addition, the traditional Feta cheese may be a source of different NSLAB genotypes to make cheese with sensorial peculiarities appropriate for each area

Protease, peptidase and esterase activities by lactobacilli and yeast isolates from Feta cheese brine

Aims: The study of peptidase, esterase and caseinolytic activity of Lactobacillus paracasei subsp. paracasei, Debaryomyces hansenii and Sacchromyces cerevisiae isolates from Feta cheese brine. Methods and Results: Cell-free extracts from four strains of Lact. paracasei subsp. paracasei, four strains of D. hansenii and three strains of S. cerevisiae, isolated from Feta cheese brine were tested for their proteolytic and esterase enzyme activities. Lactobacillus paracasei subsp. paracasei strains had intracellular aminopeptidase, dipeptidyl aminopeptidase, dipeptidase, endopeptidase and carboxypeptidase activities. Esterases were detected in three of four strains of lactobacilli and their activities were smaller with higher molecular weight fatty acids. The strains of yeasts did not exhibit endopeptidase as well as dipeptidase activities except on Pro-Leu. Their intracellular proteolytic activity was higher than that of lactobacilli. Esterases from yeasts preferentially degraded short chain fatty acids. Lactobacilli degraded preferentially beta-casein. Caseinolytic activity of yeasts was higher than that of lactobacilli. Conclusions: The results suggest that Lact. paracasei subsp. paracasei and yeasts may contribute to the development of flavour in Feta cheese. Significance and impact of the Study: Selected strains could be used as adjunct starters to make high quality Feta cheese

Preservation of pears in water in the presence of Sinapis arvensis seeds: A Greek tradition

In this research, the microbiological and physicochemical changes during preservation of pears in water in the presence of Sinapis arvensis seeds (PWS FL) according to the traditional Greek home food manufacture were studied. Pears preserved in water served as control (PW FL). The growth of lactic acid bacteria (LAB) coming from the pear surface was enhanced in the presence of Sinapis seeds, while Enterobacteriaceae and Gram-negative bacteria declined coincidently with the lower (P<0.05) pH of the PWS FL. LAB predominated over the other microbial groups in the fermentation liquids (FLs) of both systems. All the 49 LAB isolates from one fermentation experiment were identified as Leuconostoc mesenteroides subsp. cremoris by the SDS\u2013PAGE of whole-cell proteins, while RAPD-PCR fingerprinting and partial 16S rRNA sequence determination of selected isolates did not discriminate them at the subspecies level. Fruit preserved in PWS FL had higher titratable or volatile acidity, phenolic compounds or antioxidant capacity as well as lower pH and firmness than the control fruit. All physicochemical parameters of the FLs increased except of the pH which decreased. Coincidently with higher population of LAB in PWS FL the levels of citric, lactic and acetic acid were higher than in control. Oxalic acid and related unknown substances were found at higher levels in PWS FL than the control and may be the agent(s) enhancing the growth of LAB and/or contributing partially to the decline of Enterobacteriaceae. The organoleptic test showed that fruit preserved in PWS FL had better overall acceptance than the control, and that it retained most of the positive traits

\u201cGraviera Naxou and Graviera Kritis Greek PDO cheeses: Discrimination based on microbiological and physicochemical criteria and volatile organic compounds profile\u201d

The purpose of the present investigation was to study the microbiological and physicochemical characteristics of Graviera cheese from raw milk, Graviera Naxou and Graviera Kritis, made in each of the respective islands, in order to discriminate those two types of cheeses. Totally, 103 Non Starter Lactic Acid Bacteria (NSLAB) isolates were obtained from fresh cheeses and after grouping by SDS-PAGE, selected strains were identified by 16S rRNA gene sequencing analysis. In Graviera Naxou leuconostocs and Lactobacillus brevis predominated. In Graviera Kritis lactococci predominated while enterococci and leuconostocs constituted a significant part. Mature Graviera Kritis cheeses had lower (P<0.05) moisture, salt-in-moisture, aminoacid content and caseins (CN) degradation. NSLAB from Graviera Naxou had stronger mean acidifying ability at 24 h than Kritis's, exhibited higher proteolysis, but lower antagonistic activity against undesirable bacteria. The profile of total microbiota by Denaturing Gradient Gel Electrophoresis (DGGE-PCR) suggested differences in the cheeses of the two islands, while profiles of NSLAB were more similar but not their composition and evolution. Each island had its own volatile organic compounds (VOCs) profile. Acids, esters and alcohols were the most abundant groups of VOCs. There were compounds common for both cheese types and others discriminant for each area. There were also common terpenes between pasture samples and the cheeses. The overall findings indicate that Graviera Naxou and Kritis cheeses differ considerably in respect of microbiological and physicochemical criteria, as well as VOCs content