Dietary Inclusion of Stabilized Partially Destoned Olive Cake in Grazing Dairy Ewes Preserves Cheese Quality While Modulating the Sensory Profile of Pecorino Siciliano PDO Cheese

This study evaluated the effects of dietary inclusion of stabilized, partially destoned olive cake (PDOC) on bulk milk characteristics and the physicochemical, microbiological, and sensory properties of Pecorino Siciliano PDO and Ricotta cheeses. A total of 124 Valle del Belice dairy ewes were randomly assigned to two homogeneous groups according to parity (≥3rd lambing), days in milk (60 ± 5), and milk yield (1.48 ± 0.4 kg/day). Both groups grazed the same pasture and were supplemented with 0.5 kg/head/day of concentrate, either without PDOC (CTR) or containing 17% PDOC on an as-fed basis (EXP). The concentrates were formulated to be isoenergetic. Milk was collected fortnightly from morning and evening milkings, pooled by treatment, and used for cheesemaking. Bulk milk, feeds, and PDOC were analyzed for chemical composition. Fresh Ricotta and 6-month-ripened Pecorino Siciliano PDO cheeses were evaluated for composition, fatty acid (FA) profile, microbiological characteristics, and sensory properties. Data were analyzed using the MIXED model. Dietary treatment did not affect bulk milk composition but improved milk coagulation properties. Likewise, composition, titratable acidity, color, and hardness were unaffected by dietary treatment. Total phenolic content (TPC), peroxide value, and thiobarbituric acid-reactive substances in Pecorino cheese did not differ between treatments, whereas Ricotta from the CTR group unexpectedly exhibited a higher TPC than that from the EXP group (p < 0.01). Dietary inclusion of PDOC affected only a limited number of fatty acids, resulting in lower (p < 0.05) total MUFA and MCFA contents in the EXP group. Raw milk from EXP ewes showed higher counts of total mesophilic bacteria and lactic acid bacteria (p < 0.05); however, microbial populations became comparable after contact with the wooden vat and remained similar throughout ripening (p > 0.05), with no pathogenic bacteria detected in either group. Sensory analysis revealed differences in the sensory profile of Pecorino cheeses produced from EXP milk (p < 0.05), although overall acceptability did not differ between treatments. In conclusion, dietary inclusion of PDOC in dairy ewe diets appears to preserve the composition, safety, and overall acceptability of Pecorino Siciliano PDO and Ricotta cheeses.