Biofunctional stirred yoghurt production using Mangosteen (Garcinia mangostana L.) peel powder extrac

Abstract

Mangosteen (Garcinia mangostana L.) peel powder (MPP) extract was incorporated to develop stirred yoghurt rich in functional properties. Mangosteen peels are seasonal agricultural waste, rich in phenolic compounds and antioxidant activity. Ethanol (80%) with MPP (10:1) extract was prepared. Stirred yoghurt was produced using pasteurized cow- milk (3.25% fat, 23% total solids) incorporating 1.0, 1.5 and 2.0 mL of MPP extract/kg of yoghurt mixture as treatments. Sensory evaluation in a nine-point hedonic scale was conducted to determine the best level of MPP extract that suit the best sensory attributes in stirred yoghurt. The control was prepared without MPP extract. Total phenolic content (TPC, measured as mg GAE/g) and antioxidant activity of MPP extract and the treatments were determined using the standard procedures. pH profile during storage of yoghurt, physiochemical analysis, and microbiological parameters was determined. Data were analyzed by Kruskal-Wallis test, nonparametric one-way ANOVA test at p<0.05. Among all treatments, MPP extract-treated (1.5 mL/kg) yoghurt was selected as the best. TPC of MPP treated sample and control showed 3.88±0.14 and 2.5±0.04 respectively, where treated sample showed the highest TPC value. MPP extract of 1.5 mL/kg of yoghurt mixture was insufficient to provide a substantial antioxidant activity in the yoghurt whereas, it was sufficient to ensure the organoleptic acceptability and microbiological safety of stirred yoghurt. pH reduction was significantly higher (p<0.05) in the best treatment compared to the control samples. Even though the acceptability of the sample was lower than the control due to the presence of noticeable aftertaste, the best-selected yoghurt with MPP extract 1.5 mL/kg possessed 26 days of shelf life compared to the control (24 days) at 4±1 ◦C without preservatives.