From By-Product to Value: Impact of Spent Myrtle Berries on the Quality of Sheep-Milk Yoghurt.

In this study, yoghurt from sheep milk was formulated with spent myrtle berry (SMB) powder to enhance its polyphenol content and antioxidant activity. The incorporation of SMB powder into sheep milk yoghurt had a significant effect on its technological properties. Despite the increase in total polyphenols (8.46 mg/100 g FW vs. 1.35 mg/100 g FW in the control) and consequently in the antioxidant activity (1.76 vs. 0.41 in the control), SMB powder caused a substantial alteration of the yoghurt structure, resulting in a reduction in firmness and stickiness of 52.4% and 61% and a threefold increase in syneresis compared to the control, consequently leading to a reduction in gel strength. The analysis of the microstructure revealed a disruption of the protein network that weakened the gel microstructure. Consequently, subsequent studies will be dedicated to the optimisation of the process through the incorporation of thickening agents to enhance consistency and increase the water-holding capacity. Conversely, the incorporation of SMB into yoghurt did not result in a detrimental impact on sensory quality. The present study is the first to demonstrate the potential of SMB powder as a sustainable functional ingredient in dairy applications.