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The effect of the addition of rennet from different origin (animal, plant and microbial) on the release of potential antioxidant peptides was evaluated in hard cow milk cheese. After cheese making, chemical parameters, colour, TBARs and riboflavin content were determined in the final product. Antioxidant activity of the water soluble extracts from cheese was evaluated by the DPPH radical scavenging and metal chelating activity assays. Separation of peptide fractions (<3 kDa) was performed by RP-HPLC and fractions with potential antioxidant activity were analyzed by LC-MS/MS for further identification of peptides. Results suggested that colour and riboflavin content were affected by the type of rennet used (P <.05). On the other hand, extracts of cheese with microbial rennet showed the highest antioxidant activity (P <.05). Only nine fractions isolated from the extracts showed either DPPH radical scavenging or metal chelating activities. Peptides EIVPN and DKIHPF, previously reported in other studies by showing ACE-inhibitory activity, were identified in these fractions and revealed high metal chelating activity. Moreover, a new peptide, with also high metal chelating activity, has been identified (VAPFPQ). In conclusion, it would be worthwhile to synthesis these peptides and confirm their antioxidant and metal chelating activities. Unlabelled Image • Cheese made with animal rennet showed higher reduction of riboflavin. • Extracts from cheese with microbial rennet showed the highest antioxidant activity. • Peptides EIVPN and DKIHPF, previously reported, revealed high metal chelating activity. • A new peptide, with high metal chelating activity, has been identified (VAPFPQ). [ABSTRACT FROM AUTHOR]

Forty enterococci isolated along the production chains of three traditional cheeses (PDO Pecorino Siciliano, PDO Vastedda della Valle del Belìce, and Caciocavallo Palermitano) made in Sicily (southern Italy) were studied for the assessment of their antibiotic resistance and virulence by a combined phenotypic/genotypic approach. A total of 31 Enterococcus displayed resistance to at least one or more of the antimicrobials tested. The strains exhibited high percentages of resistance to erythromycin (52.5%), ciprofloxacin (35.0%), quinupristin–dalfopristin (20.0%), tetracycline (17.5%), and high-level streptomycin (5.0%). The presence of tet (M), cat (pC221), and aad E genes for resistance to tetracycline, chloramphenicol, and streptomycin, respectively, was registered in all strains with resistance phenotype. The erm (B) gene was not detected in any erythromycin-resistant strain. The Enterococcus strains were further tested by PCR for the presence of virulence genes, namely, gel E, asa1 , efaA , ace , and esp . Twenty strains were positive for all virulence genes tested. Among the enterococci isolated from final cheeses, three strains (representing 33.3% of total cheese strains) were sensible to all antimicrobials tested and did not carry any virulence factor. Although this study confirmed that the majority of dairy enterococci are vectors for the dissemination of antimicrobial resistance and virulence genes, only two strains showed a high resistance to aminoglycosides, commonly administered to combat enterococci responsible for human infections. Furthermore, the presence of the strains E. casseliflavus FMAC163, E. durans FMAC134B, and E. faecium PON94 without risk determinants, found at dominating levels over the Enterococcus populations in the processed products, stimulates further investigations for their future applications in cheese making. All strains devoid of the undesired traits were isolated from stretched cheeses. Thus, this cheese typology represents an interesting environment to deepen the studies on the risk/benefit role of enterococci in fermented foods for their qualified presumption of safety (QPS) assessment. [ABSTRACT FROM AUTHOR]

Total fatty acids were determined in Los Pedroches cheese samples manufactured with either animal or vegetable rennet during 100 days of ripening, using gas-liquid chromatography. Data of crude fat and of 24 relationships between fatty acids, have been calculated. No statistically significant differences were found for effect of rennet type or ripening time on esterified fatty acids composition of the cheese.