Effect of traditional thermal and high-pressure processing (HPP) methods on the color stability and antioxidant capacities of Djulis (Chenopodium formosanum Koidz.)

Abstract

Betanin is a major pigment that contributes to it's color and antioxidant capacity of Djulis (Chenopodiun formosaneum Koidz.,) grains. However, betanin becomes unstable during thermal processing. Therefore, we investigated the effect of high-pressure processing (HPP: 500 MPa at 10 °C and 30 °C for 3 min) on the microbial load, pigment, and antioxidant capacity of Djulis whole grain, hull, and de-hulled seeds as an alternative to traditional thermal methods (cooking for 20 min and pasteurization at 65 °C/30 min). Correlation and principal component analysis (PCA) were performed to understand the effect of HPP on the quality of Djulis. Results showed that HPP decreased the microbial load and retained >85% of betanin as well as higher antioxidant capacity. Betanin was highly correlated with total phenolic and antioxidant capacities (r = ≥ 0.98, p < 0.01). PCA exclusively separated the thermal and HPP whole grain samples using two components (PCs 1 (40.88%) and 2 (25.59%)). Therefore, HPP may retain more pigment and antioxidant capacities, thus it could be an alternate processing method to develop Djulis products.