Introduction: The bread-making properties of 100% rice flour, used to prepare gluten-free bread, is poor. Heat-responsive xyloglucan (MTG), which exhibits gel-forming properties upon heating, is expected to enhance bread-making properties; however, there are no reports on its use in rice flour bread. Therefore, this study investigated the effects of adding various thickening polysaccharides, including MTG, on the dough properties, bread-making properties, staling characteristics, and sensory acceptability of gluten-free rice flour bread.

Methods: Rice flour bread was prepared by adding MTG, tamarind gum (TG), and xanthan gum (XT) at a 1.0% ratio to rice flour, along with additional ingredients including dry yeast, granulated sugar, salt, and olive oil. It was then baked in a 200°C oven for 14 minutes. Rice flour steamed bread was prepared by substituting baking powder with dry yeast in the rice flour bread ingredients and microwaving at 600 W for 7 minutes. These breads were stored for 48 hours at 25°C and 65% relative humidity to examine the changes in physical properties and staling characteristics arising from storage. Sensory evaluation was also conducted to assess acceptability.

Results: The flow characteristics of the rice flour dough showed dilatancy similar to the control and MTG-added samples, indicating that the dough reflected the properties of starch. The specific volume of rice flour bread was significantly lower in the MTG-added sample; however, for steamed rice flour bread, the MTG-added sample was equivalent to the XT-added sample and was larger than that of the control. The apparent elastic modulus and stress at 40% compression of rice flour bread and steamed bread samples containing thickened polysaccharides were lower than those of the control after 3 days of storage. In rice flour bread, the addition of MTG and TG suppressed the hardening effect. Evaluation of the retrogradation of rice flour bread using X-ray diffraction revealed that the relative strength of the control sample was highest on the 3rd day of storage, whereas the MTG-added sample showed the lowest relative strength. In steamed bread, the addition of thickening polysaccharides suppressed retrogradation; however, no difference was observed between the types of thickening polysaccharides used. In the sensory evaluation, MTG-added rice flour bread and steamed bread were rated as softer than the control, even after 2 days of storage. The MTG-added steamed bread was rated as the softest compared to all other samples. These results demonstrate that adding MTG to rice flour bread suppresses bread hardening and retrogradation and enables the preparation of gluten-free rice flour products with excellent baking characteristics and high palatability, particularly when steamed.

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