084: Oxidative Stability of Rice Flour From Rice Bran With or Without Lipoxygenase Activity Under Thermal Oxidation and Light Irradiation

Introduction

Lipoxygenase in rice flour catalyzes lipid oxidation of polyunsaturated fatty acids including 1,4-pentadiene structure under aerobic conditions. Lipid oxidation is one of key chemical reactions influencing the quality of rice flour during storage. Therefore, it is important to regulate the activity of lipoxygenase in rice flour. Baromi 2 is a rice variety developed for its soft crystal structure to make flour production efficient, and Jeonju 695 is a rice variety with inactivated lipoxygenase in Baromi 2. The objective of this study was to determine the oxidative stability of rice flours according to lipoxygenase under autoxidation and light irradiation.

Methods

Oxidative stability of 2 rice flours including Baromi 2 (B2) and Jeonju 695 (J695) were determined under autoxidation and light irradiation. Degree of autoxidation was evaluated in rice flour stored at 60℃ and degree of photooxidation was evaluated in rice flour stored under fluorescent light of 1330lx at 25℃. To evaluate the degree of oxidation, headspace oxygen was analyzed, and an electronic nose was used to observe the similarity of rice flour by PCA and distance from control during each storage period.

Results

During autoxidation, the headspace oxygen content of B2 decreased from 20.7% to 13.7% and that of J695 decreased to 14.8% for 70-day storage. During photooxidation, the headspace oxygen content of B2 decreased from 20.7% to 13.5% and that of J695 decreased to 15.9% for 18 day storage. In autoxidation and light irradiation, most of samples showed a pattern of moving away from the control based on the results of electronic nose test. Under both oxidation conditions, the distance difference between B2 and control than that of J695 was greater during the storage.

Significance

These results showed that lipoxygenase inactivation can increase the oxidative stability in rice flour during storage under autoxidation and light irradiation. Therefore, rice flour should be stored in dark and low temperature conditions to maintain quality during storage.

Authors: JungMin Lee, Dowon Kim, DongChan Choi, and JaeHwan Lee