Effects of using microfiltration technique in production of herby cheese on metagenomic characteristics, general quality and maturation of cheese

In the research, 3 different cheeses (MR, MRO and MROS) were produced with the combination of rennet (R), herb (O) and starter culture (S) from microfiltered (M) milk using a ceramic membrane with a pore diameter of 1.2 µm. As control cheese samples, 2 cheeses (CR and CRO) were produced with the combination of rennet and herb in raw milk and 1 cheese (PROS) was produced with the combination of rennet, herb and starter in pasteurized milk (P). The cheeses were ripened at two different storage temperatures (refrigerator (D): 6℃; room (O): 14℃). Thus, the study was conducted on a total of 12 different cheeses. Physical, chemical, biochemical, volatile components, free fatty acid content, electrophoretic and sensory analyses were performed on the cheese samples produced on the 1st, 30th, 60th and 90th days of storage. Cheese analyses were carried out in two replications. Cheese samples were analyzed by taking 6 cheese samples on the 1st day of storage and 12 cheese samples matured at both 14.2℃ and 6℃ on the 90th day of storage. 16S Amplicon metagenomic analysis from next generation gene sequencing methods was carried out for a total of 18 cheese samples. It was determined that dry matter, fat, protein, ash, salt contents, titratable acidity, pH, lipolysis, lipolysis parameters (KZSYA, OZSYA, UZSYA, DoySYA, DoymaSYA and TopSYA), proteolysis criteria (SCN, TCA-CN and PTA-CN), hardness and volatile component contents of cheese samples were greatly affected by storage time, storage temperature and pretreatments applied to milk. It was seen that the cheeses matured at 14.2℃ and produced by microfiltration had generally higher values of the mentioned criteria than the cheeses matured at 6℃. As a result of 16S Amplicon metagenomic analysis, it was determined that 10 phylum were identified in the test cheeses and the dominant phylum was Bacillota. In the cheeses, Streptococcaceae was the family that was found in the phylum Bacillota and had the highest abundance level. Among the trial cheeses, it was determined that Streptococcus was the dominant bacteria taxon in 1st day MROS cheese and 90th day MRO cheese at room temperature, while Pediococcus was the dominant bacteria taxon in 90th day MRO and MROS cheeses at refrigerator temperature. The genus with the highest abundance in other cheeses was determined to be Lactococcus. Among the cheese samples, it was determined that Pediococcus ethanolidurans was the most abundant bacteria species in MRO and MROS cheeses at 90th day refrigerator temperature; Streptococcus parasuis was the most abundant bacteria species in 1st day MROS and 90th day room temperature MRO cheeses. Lactoccus cremoris was found to be the most common dominant species in cheeses other than the mentioned cheeses. It was observed that the dominant species changed in some cheeses produced by microfiltration process, the rate of Lactoccus cremoris was higher in cheese samples with starter added, cheeses ripened at room temperature generally contained more ratios of species compared to those ripened in the refrigerator, and both species ratios and species diversity changed as the ripening period progressed. The research findings revealed that produced by microfiltering (1.2 µm) raw milk in a ceramic membrane unit operating according to the cross-flow basis showed similar or close physical, chemical, biochemical, free fatty acid, volatile component contents and sensory properties to the cheeses produced from control raw milk in generally, and that this application can be applied as an alternative to the Herby cheese making technique produced from pasteurized and raw milk.