Orange Peel Feed Ingredient in Lactating Ewes: Effect on Yoghurt Chemical Composition, Fatty Acid Profile, Antioxidant Activity, Physicochemical Properties, and Sensory Quality

This study examined the effects of incorporating processed (hydrolysed) (POP) and unprocessed (non-hydrolysed) (UOP) orange peels into the diets of lactating ewes on the proximate composition, fatty acid profile, antioxidant properties, physicochemical characteristics, and sensory attributes of traditional sheep milk yoghurt. Thirty-six Chios breed ewes were divided into three dietary groups: POP, UOP, and a conventional control diet (Control). Yoghurt produced from the UOP and POP diets had higher protein content (5.93 and 5.53%, respectively) and fat content (6.79 and 6.24%, respectively) compared to the Control (5.42% for protein and 6.06% for fat). Additionally, there were no significant differences in the nutritional indices of yoghurt fat. The determination of antioxidant activity showed no significant differences among the groups using the ABTS, DPPH, and FRAP methods, whereas significant differences were observed when measured with the Folin–Ciocalteu method. Textural analysis revealed that UOP yoghurt had greater firmness and cohesiveness. The whiteness index of yoghurt across all treatments remained consistent during storage, maintaining the desirable visual characteristics of traditional sheep milk yoghurt. Syneresis levels were similar across all groups, indicating no negative effects on yoghurt stability. Sensory evaluation confirmed the high acceptability of yoghurt produced from both experimental diets. These findings highlight the potential of orange peels as a sustainable feed additive, with no adverse effects on the nutritional, functional, or sensory properties of dairy products, while contributing to effective waste valorisation.