Antioxidant activity and some quality characteristics of buffalo yoghurt fortified with peanut skin extract powder

Peanut is an important crop grown worldwide. Peanut skin, the byproduct of peanut processing is a valuable byproduct due to its content of many functional components. Therefore, this study aimed to evaluate the effect of fortification of yoghurt with peanut skin extract powder (PSEP) at 50, 100 and 200 mg/L milk on the antioxidant activity (radical scavenging activity RSA%) and some quality characteristics of the resultant yoghurt during cold storage. The obtained results revealed that total phenolic content of PSEP is 109.46 mg GAE/g while it’s radical scavenging activity % reached 90.57%. Fortification of yoghurt with PSEP increased the apparent viscosity, antioxidant activity, and total phenolic, acetaldehyde, and diacetyl contents as compared to control, while the syneresis of fortified yoghurt was reduced. Microbiological analysis showed that fresh control yoghurt had the highest counts of Streptococcus thermophilus and Lactobacillus bulgaricus and decreased at the end of storage in all treatments. Both control and T1 (the low concentration of PSEP) gained the highest acceptability; therefore, it was recommended that fortification of yoghurt with 50 mg of PSEP/L is more preferable than the other concentrations. In addition, it could be considered as a natural antioxidant source in formulating functional yoghurt either in industrial and/or small industrial scale.