Effect of forage type, season, and ripening time on selected quality properties of sheep milk cheese

The aim of this research was to study changes in the microbial populations, free AA profile, biogenic amine content, and sensory characteristics of ripened cheeses (100 and 180 d) produced in different seasons (summer, autumn, winter, and spring) from pasteurized sheep milk from 8 commercial flocks fed hay or silage diets. Twenty-one individual AA and 6 biogenic amines were determined by ultra-high performance liquid chromatography. Type of conserved forage for sheep feeding did not affect the variables studied, which is of great interest because hay and silage are low-cost ingredients for sheep feeding. Proteolysis led total free AA concentrations ranging between 35,179.26 and 138,063.71 mg/kg of cheese at 180 d of ripening. γ-Aminobutyric acid, which has been associated with beneficial effects on human health, was the second most abundant AA in all cheese samples, accounting for 15% of total free AA. Spring cheeses showed 2-fold higher concentrations of γ-aminobutyric acid than summer and autumn cheeses at the end of ripening. Overall, spring, winter, and autumn cheeses had lower average concentration of biogenic amines (431.99 mg/kg of cheese) than summer cheeses (825.70 mg/kg of cheese) as well as better sensory characteristics. Therefore, this study could provide the dairy industry with useful information for producing cheeses with valuable nutritional and sensory quality for consumers.