Effects of Indica Black Rice, Konjac Powder and Water on the Quality Characteristics of Gluten-Free Taichung Sen 17 Rice Bread

Rice is a safe and widely consumed gluten-free grain; however, breads prepared from white rice flour, such as Taichung Sen 17 (TS17), are prone to rapid staling and typically lack sufficient dietary fiber and bioactive compounds. To address these limitations, this study investigated the effects of partially replacing TS17 flour with indica black rice (B) flour, varying water content, and incorporating the natural hydrocolloid konjac glucomannan (K) on the quality of rice batter and bread. Compared with TS17 flour, B flour contained higher levels of total dietary fiber, total phenols, total anthocyanins, and antioxidant capacity. Substituting 15% of TS17 with B flour slightly increased the bread volume from 1032 mL to 1042 mL under 92% water addition (1.01-fold). More notably, it significantly increased the volume from 872 mL to 917 mL under 107% water (1.05-fold), and from 642 mL to 775 mL under 122% water (1.21-fold). However, higher substitution levels of B flour resulted in a reduction in loaf volume. Further incorporation of 2% K under 122% water conditions (TS17B15K2.0-122) resulted in the highest loaf volume of 1063 mL, representing a significant 1.37-fold increase compared to TS17B15-122 (775 mL), and exhibited the slowest staling rate after 24 h. Although K significantly improved bread texture and moisture retention, excessive addition may accelerate staling due to insufficient water availability in the formulation. These findings highlight that combining TS17 flour, B flour, and konjac gum represents a feasible and sustainable strategy for developing functional gluten-free baked products targeted at health-conscious and gluten-intolerant consumers.