Improving the quality of gluten-free and additive-free rice bread using mutant varieties with short amylopectin side chains

Abstract

The purpose of this study was to clarify the conditions under which gluten-free and additive-free breads can be prepared by mixing two types of rice flour. Rice flour of “Mizuhochikara,” a variety suitable for making rice-flour bread, was mixed with rice flour from either “Yawaramaru,” a non-glutinous variety with a high amylopectin short chain ratio, or “Yawakoimochi,” a glutinous variety with a high amylopectin short chain ratio. When “Yawaramaru” rice flour was used, the specific volume was more than 4.0 mL/g at a substitution rate of up to 40 %. The firmness of bread made with 40 % “Yawaramaru rice” flour after 3 days of storage was about 18 % lower than that of bread made with “Mizuhochikara” rice flour only (p < 0.05). When “Yawakoimochi” rice flour was used, the specific volume was about 3.3 mL/g at a substitution rate of 20%; however, at higher substitution rates, the loaves had significantly less volume. The firmness of bread made with 20 % “Yawakoimochi” rice flour after 3 days was about 18 % lower than that of bread made with “Mizuhochikara” rice flour only (p < 0.01). These results indicate that using rice flour with a high percentage of short amylopectin side chains can suppress bread aging to some extent without the addition of additives such as thickening agents.