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Total phenolic content (TPC) and antioxidant properties of xanthone extract from mangosteen pericarp via microwave-assisted extraction (MAE) method was optimized by response surface methodology (RSM). The MAE extraction conditions to obtain optimum antioxidant-rich xanthone extract were at 2.24 min of irradiation time, 25 mL/g of solvent-to-solid ratio and 71% of ethanol concentration. The predicted results for four responses were as follows; 320.31 mg gallic acid equivalent/g extract, 83.63% and 93.77% inhibition (DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-Azino-bis-3-ethylbenzthiazoline-6-sulfonic acid) assays), and 144.56 mg Trolox equivalent/g extract (FRAP, Ferric reducing antioxidant power). The predicted and actual values were statistically insignificant (P > 0.05). Therefore, these results confirmed that the examined model was acceptable and relevant. MAE led to a slightly similar antioxidant capacity and a higher extraction of α-mangostin, a major xanthone of mangosteen pericarp as compared to water bath-maceration technique.

A simple tensile test set-up was built and attached to an Instron 5566 to determine gluten extensibility, comparing the performance of strong and weak flour mixed for various mixing time. In this work, the gluten strip was clamped at two ends and extended upward at the centre by a hook at speed of 300 mm min À1 . Parameters such as gluten length at fracture, measured force, actual force acting on the gluten strips, strain, strain rate and stress were obtained. Gluten obtained from strong flour has greater extensibility compared to weak flour. The extensibility of gluten from both strong and weak flour dough increased as dough mixing time increased before decreasing at a peak of 8 min. The results demonstrated the capability of the tensile test set-up to describe the development of gluten during mixing of dough. Rheological characteristic of gluten indicated that gluten exhibited strain hardening effect during extension.