Effect of water blanching on phenolic compounds, antioxidant activities, enzyme inactivation, microbial reduction, and surface structure of samnamul (Aruncus dioicus var kamtschaticus)

Water blanching is widely used in food industry, but imprudent process causes considerable quality deterioration. To determine optimum condition, the effect of water blanching at different temperature (80, 90 and 98 °C) and time (0–10 min) on the characteristics of samnamul was investigated. Total phenolic and flavonoid content and antioxidant activities showed dramatic increase up to maximum and decreased rapidly as further blanching prolonged at all temperatures. The blanching at 98 °C for 30 s showed the highest values of them. Phenolic compounds such as shanzhiside methyl ester, isoquercetin, quercetin 3-O-rhamnoside, kaempferol 3-O-glucoside and sergeolide showed different temperature dependence. At 30 s, quercetin derivatives levels increased with increasing temperature and showed highest heat-stability. Based on our study, the blanching at high temperature of 98 °C for a short time of 30 s may be important to increase or maintain nutritional quality, while oxidative enzyme activities and the microorganism numbers decreased.