Abstract:
Functional stirred yoghurt rich in phenolic antioxidants was developed using a seasonal agricultural waste, mangosteen (Garcinia mangostana L) peels. The peels were dried at 50°C in a laboratory iven to a moisture content of 10%, ground and sieved to obtain a fine powder. Eighty percent ethanol extract of mangosteen peel powder (MPP) was prepared and stored in dark bottles at 4 ± 1 °C until further analysis. Yoghurts were prepared using pasteurized fresh cow milk standardized to 3.25% fat, by incorporating different levels {O (control), 1.0, 1.5 and 2.0 mg} of MPP extract (MPPE)/kg of yoghurt mix. The mix was inoculated at 42 ± 1 °C with a commercial yoghurt culture and incubated until pH decreased to 4.6. Suitable level of MPPE that was to be incorporated into the yoghurt was determined using a sensory evaluation. Proximate composition, total phenolic content (TPC) and antioxidant activity (radical scavenging activity (RSA %)] of MPPE and yoghurts were determined using standard procedures. Dry matter, moisture, protein, fat and ash percentages of MPP were 91.39 ± 0.18, 8.61 ± 0.18, 5.68 ± 0.05, 2.41 ± 0.34 and 4.19 ± 0.17, respectively. Total solids, moisture, fat and protein of selected vs. control yoghurt were 23.42 ± 0.05 vs. 21.84 ± 0.04, 76.57 ± 0.56 vs. 78.17 ± 0.04, 3.24 ± 0.04 vs. 3.23 ± 0.02 and 5.12 ± 0.05 vs. 5.32 ± 0.04, respectively. Total phenolic content detected in MPPE, selected and control yoghurts were 115.10 ± 0.05, 3.88 ± 0.14 and 2.5 ± 0.04 mg GAE/g of product, respectively. Antioxidant activity detected in MPPacceptable, microbiologically safe stirred yoghurt with significantly (p<0.05) less whey syneresis could be developed by incorporating MPPE at 1.5 ml/kg of yoghurt mix. However, this level was observed to be insufficient to produce yoghurt having sufficient antioxidant activity. Yoghurt with added MPPE had a better shelf life of 26 days compared to the control having 24 days at 4 ± 1 °C without the use of preservatives. Further studies are needed to develop a yoghurt incorporating MPPE with high antioxidant activity.E was 57.81 ± 6.56% and it was not detected in yoghurt samples. Organoleptically
