The microbiology of Kasseri cheese during the maturation

The microbiology of Kasseri cheese, a Protected Designation of Origin (PDO) cheese of pasta-filata type was studied in order to identify the dominant species and strains that may contribute to the maturation process. Chemical composition and microbiological quality of Kasseri cheese samples from two different dairies during the maturation was studied at 0, 7, 25, 60 and 90 days of the maturation. Lactic acid bacteria and Enterococcus spp. were found to be the dominant microflora in fresh cheese. P. pentosaceous and P. acidilactici, E. hirae, E. faecium, E. durans and E. gallinarium, together with facultatively heterofermentative lactobacilli were found to be the dominant microflora. Since these strains are dominating the microflora of Kasseri cheese during maturation, the enzymic system need to be further studied in order to select the proper strains for adjunct culture in Kasseri cheese.

Adjunct Culture of Non-Starter Lactic Acid Bacteria for the Production of Provola Dei Nebrodi PDO Cheese: In Vitro Screening and Pilot-Scale Cheese-Making

The present study aimed at selecting non-starter lactic acid bacteria strains, with desirable technological and enzymatic activities, suitable as adjunct culture for the Provola dei Nebrodi cheese production. One hundred and twenty-one lactic acid bacteria, isolated from traditional Provola dei Nebrodi cheese samples, were genetically identified by Rep-PCR genomic fingerprinting, using the (GTG)5-primer, and by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). Twenty-seven strains, included in the qualified presumption of safety (QPS) list, were tested for technological and proteinase/peptidase activities. Results showed that technological features and flavour formation abilities were strain-dependent. Among the selected strains, Lacticaseibacillus paracasei PN 76 and Limosilactobacillus fermentum PN 101 were used as adjunct culture in pilot-scale cheese-making trials. Data revealed that adjunct cultures positively affected the flavour development of cheese, starting from 30 days of ripening, contributing to the formation of key flavour compounds. The volatile organic compound profiles of experimental cheeses was significantly different from those generated in the controls, suggesting that the selected adjunct strains were able to accelerate the flavour development, contributing to a unique profile of Provola dei Nebrodi cheese.

Application of Enterococcus faecium KE82, an enterocin-A-B-P-producing strain, as an adjunct culture enhances inactivation of Listeria monocytogenes during traditional PDO Galotyri cheese processing

The ability of the enterocin-A-B-P-producing Enterococcus faecium KE82 adjunct strain to inactivate Listeria monocytogenes during Galotyri PDO cheese processing was evaluated. Three artisan cheese trials from traditionally ‘boiled’ (85oC) ewe’s milk were processed. The milk cooled at 42oC was divided in two parts: A1 was inoculated with Streptococcus thermophilus ST1 and Lactococcus lactis subsp. cremoris M78, and A2 with the basic starter ST1+M78 plus the KE82 adjunct (step 1). All milks were fermented at 20-22oC for 24 h (step 2); the curds were drained at 12oC for 72 h (step 3) and then salted with 1.5-1.8% salt to obtain the fresh Galotyri cheeses (step 4), which were ripened at 4oC for 30 days (step 5). Because an artificial listerial contamination in the dairy plant was prohibited, A1 and A2 cheese milk (200-mL) or curd (200-g) portions were taken after steps 1 to 5, inoculated (3-4 log CFU/mL or g) with L. monocytogenes no.10, incubated at 37, 22, 12, and 4oC for predefined periods, and analyzed microbiologically and for pH. L. monocytogenes declined without growth in all cheese curd portions contaminated after steps 2 to 5 (pH 4.36 to 4.84), when stored at 4 or 12oC for 15 days. The final net reductions of Listeria populations were by 2.00, 1.07, 0.54 and 0.61 log units higher in the A2 than A1 curd portions after steps 2, 3, 4 and 5, respectively. As regards step 1 conducted in simulation of the whole cheese milk fermentation process, L. monocytogenes declined by 1.47 log units more in the A2 than A1 milk portions after 72 h at 22oC; however, a slight (0.6-log) growth was preceded during the first 6 h at 37oC. In conclusion, E. faecium KE82 showed growth compatibility with the starter and enhanced inactivation of L. monocytogenes across Galotyri cheese processing. Combined acid-enterocin antilisterial effects were the weakest in the fermenting milks, turned to the strongest in the unsalted fermented curds, and reduced in the salted fresh cheeses.