Impact of soybean protein isolate on gluten‐free bread: a comprehensive study of physicochemical properties of gluten‐free dough and bread matrix properties

Summary Rice bread is an essential component of a healthy diet. However, due to the poor processing properties of rice protein and starch, it is difficult to form an effective gel network structure, resulting in poor quality of rice breads. This research investigated the impacts of soy protein isolate (SPI) on the physicochemical properties of rice dough and the quality of rice bread. The results suggested that adding SPI could refine the thermal stability of mixtures and delay the aging of starch compared with pure rice flour, indicating that adding SPI reduced the amylose concentration and inhibited starch interaction in the mixed rice powder system. The rheology and SEM analysis of doughs showed that the appropriate addition of SPI increased the elasticity, and reached the highest fermentation height and gas retention coefficient at 9% SPI content, which increased by 115.38% and 8.39%, respectively. In contrast, excessive SPI led to protein aggregation and weakened the structural strength of the dough. When adding 9% SPI improved the hardness, chewiness and specific volume of rice bread, significantly reduced the brightness and baking loss rate, and refined the performance and quality of rice bread. This study confirms that SPI can be used as an improver for good gluten‐free bread (GFB) through its good functional properties and action on starch and provides some basis for further investigation of the interaction between SPI as an improver and rice starch.