Non-enzymatic browning of lotus root during boiling

Abstract

Lotus root is the most consumed aquatic vegetable in China. Both the actual boiling of lotus root and the simulated boiling of its extract were performed at different conditions to explore the development of non-enzymatic browning and the loss of reducing sugars, free amino acids, total free phenols and ascorbic acid. The kinetic parameters of zero-order and first-order models indicated that both browning degree and nutrient loss had a positive correlation with boiling time, temperature and pH value. Moreover, nutrient contents and boiling conditions were adopted as independent variables to establish the multiple linear regression model of browning degree (P < 0.001), which confirmed that reducing sugars and total phenols principally contributed to the browning (P < 0.01), through caramelization and phenol oxidation. With the addition of baking soda (pH 8), 100 °C boiling decreased the DPPH radical scavenging capacity and ferric reducing antioxidant power of lotus root extract by 62.96% and 58.51%, respectively. Furthermore, 120 °C boiling probably induced the formation of browning products, which possessed cytotoxicity against HepG2 and L02 cells. A short boiling time, as well as an acidic condition induced by added vinegar, is recommended for cooking and processing of lotus root in consideration of nutrition and health.