Optimization of thermal processing conditions for brown rice noodles

Abstract

Based on the current thermal processing conditions for rice noodles (80–85 °C for 20–30 min), we used response surface methodology to find brown rice (BR) noodle processing conditions that maximize the noodles antioxidant activity, digestibility, and gelatinization. The experiments were designed according to the central composite design, including two independent variables (temperature and time) and six dependent variables [total phenolic contents (TPC), total flavonoid contents (TFC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging activities, digestibility, and gelatinization]. Antioxidant activities decreased but digestibility and gelatinization increased with increasing temperature and time. All dependent variables suggested a quadratic model except TFC, but the probability of TPC was not applicable (0.1505), and DPPH radical scavenging activity showed a relatively low R 2 (0.6750). Therefore, we applied the other three dependent variables (ABTS radical scavenging activity, digestibility, and gelatinization) to the 3D response surface and proposed three optimum conditions: (1) for antioxidant activity (70 °C, 22.95 min), (2) for digestibility and gelatinization (88.18 °C, 34.89 min), and (3) for all three variables (88.5 °C, 40 min). In a validation test, all dependent variables showed values within a 5 % error range except TFC. These results show the optimum processing conditions for BR noodles to maximize antioxidant activity and provide sustainability in BR noodle processing.