Antioxidant activities and physical properties of stirred yoghurt fortified with pomegranate peel extracts

Abstract

Pomegranate peels (outside, inside and whole) were oven (40°C) and solar dried. Aqueous and methanolic extracts were prepared from the dried peels, and their antioxidant activities [radical scavenging activity (RSA %), ABTS radical scavenging, total phenolic content (TPC) and total flavonoids content (TFC)] were determined. The aqueous extract of the dried whole peel showed the highest antioxidant activities as compared to other pomegranate peel extracts (PPEs). Stirred yoghurt was prepared from reconstituted skim milk powder fortified with 5%, 10%, 15%, 20%, 25%, 30% and 35% of the PPE, before and after inoculation with the traditional yoghurt starter. Addition of PPE before inoculation with the starter resulted in stirred yoghurt of higher antioxidant activities than that with PPE added after inoculation with the starter. Also, increasing the percentage of the added PPE increased significantly the antioxidant activities of stirred yoghurt up to 25% and further increase in the percentage of added PPE led no significant effect. Addition of PPE had no significant effects on the sensory attributes (appearance, body & texture and flavor) as compared to the control sample. Increasing the percentage of the added PPE resulted in decrease in the viscosity of the stirred yoghurt, but samples containing 20% and 25% PPE led almost the same viscosity.