Quality improvement of gluten-free rice flour bread through the addition of high-temperature water during processing

Recently, there has been an increase in the demand for gluten-free bread due to health reasons. One of the flours used to produce gluten-free bread is rice flour; flour characteristics are very important for breadmaking. Although a study has shown that the addition of high-temperature water can improve the quality of rice flour bread, studies are yet to consider different rice properties. Therefore, the aim of this study was to investigate the effect of adding high-temperature water and rice flour characteristics on the quality of rice flour bread using six commercially available rice flours. The rice flours used in the sample had amylose content from 12.1% to 24.5%, damaged starch content from 2.4% to 5.5%, mode diameter from 16.3 to 63.3 µm, protein content from 5.4% to 6.1%, and moisture content in the range of 12.0%-15.0%. The results showed that regardless of the rice characteristics, breads prepared at the optimum watering temperature were puffier and softer than those prepared using cold water (5°C). For rice flours with similar particle size, the optimal water temperature and degree of gelatinization for breadmaking increased with rice flours with lower amylose content. Furthermore, the rheological properties of dough prepared at the optimum water addition temperature were stable, with loss modulus (G″) being dominant over the entire frequency range in the frequency sweep test. Since the water temperature added to the dough affects breadmaking properties more than the characteristics of the rice flour, adjusting the water temperature may enable the production of high-quality bread even with rice flour unsuitable for making. PRACTICAL APPLICATION: Presently, the addition of high-temperature water to rice flour has been shown to improve the bread quality. In this study, we investigated the effects of high-temperature water addition on the quality of rice flour bread using rice flour varieties with different flour characteristics. Even in rice flour with small particle size and low amylose content, which is not suitable for breadmaking, bread quality can be improved by adding hot water at around 70°C. This is a simple and practical method to improve the quality of gluten-free rice flour bread without adding thickeners.