Optimization of roasting conditions through antioxidant and anti-inflammatory activities of Yak-kong (Rhynchosia nulubilis).

The effects of roasting conditions on the antioxidant activities and anti-inflammatory activities of roasted yak-kong were investigated using a second-order central composite design. The optimum conditions for DPPH radical scavenging ability (IC50), ABTS radical scavenging activity (IC50), total phenolic content (TPC), and oxygen radical absorbance capacity (ORAC) were at 111.47°C for 20.45 min, with the best values (DPPH, IC50; 2.143 mg/mL, ABTS, IC50; 1.775 mg/mL, TPC; 51.39mg tannic acid (TAE)/g, and ORAC; 6.89 μmoL trolox equivalents (TE)/g). The optimum conditions of nitric oxide (NO) production, prostaglandin E2 (PGE2) production, and tumor necrosis factor-α (TNF-α) were at 110.24°C for 21.18 min, yielding the best values (NO; 14.484 μM, PGE2; 3.433 mg/mL, and TNF-α; 3.818 ng/mL). Superimposed contour plots with regard to 7 variables indicated that the optimum roasting temperature and time were 110.88°C and 20.86 min. This result suggested that the optimally roasted yak-kong could replace coffee beans to provide potential bone health benefits to heavy coffee drinkers.