Effects of Water Soaking on Bread-Making Quality of Brown Rice Flour

Abstract

We found that brown rice flour produced using a jet mill after soaking for more than 12 h yielded a better formulation of rice/gluten bread, giving an equivalent specific loaf volume (SLV) as bread made with white rice flour. Quality analysis of the brown rice flour showed that soaking for more than 12 h resulted in a lower damaged starch content. There was a significant inverse correlation between damaged starch content and SLV. Substitution of 10% white rice flour with rice bran had little effect on final SLV. Furthermore, endogenous α-amylase activity in brown rice flour produced after soaking was approximately 5 to 12 times higher than that of white rice flour, but there was no correlation with SLV. These results indicate that the improved SLV in brown rice/gluten bread was predominantly due to the decrease in damaged starch content, which depends on soaking time.Keywords: rice bread, brown rice flour, water soaking, damaged starch *To whom correspondence should be addressed. E-mail: sty564@affrc.go.jp IntroductionRice (Oryza sativa L.) is an important source of nutrition and energy, and is one of the most suitable cereal grains used for preparing foods. Rice flour can be used as a wheat flour substitute and processed into bread. However, rice storage proteins do not possess the viscoelastic properties that are typical of wheat gluten. In wheat, gliadins (prolamins) are responsible for the dough's cohesiveness, while the glutenins (glutelins) are apparently responsible for the dough's resistance to extension (Hoseney, 1994). The gluten network constructed by these two proteins provides the dough with unique viscoelastic properties and the ability to retain gases, making it a good quality raw material for the production of yeast-leavened products. However, rice flour lacks these properties; hence, the qualities of gluten-free rice bread and wheat-rice bread with a high proportion of rice flour are generally inferior.Rice flour is used for bread-making in three flour mixtures: rice/wheat flour; rice flour/vital gluten; and gluten free. It has been reported that in the case of rice/wheat flour bread, substitution of wheat flour with up to 30% rice flour is acceptable without compromising the sensory qualities (Watanabe et al., 2004;Nakamura et al., 2009). There have been few reports on bread-making quality with the addition of

Characteristics of Rice Flour Suitable for the Production of Rice Flour Bread Containing Gluten and Methods of Reducing the Cost of Producing Rice Flour

“…However, the development of high-yield floury rice, reduction in weight loss during polishing, and/or new polishing processes are required because the floury rice yield is generally low and floury kernels are easily broken during polishing. Furthermore, the production of brown rice flour will also contribute to reducing the cost of producing rice flour because no polishing processes are required (Hamada et al 2012). Brown rice flours can be produced using a jet mill after soaking for more than 12 h. In addition, brown rice flours can provide added value and make the rice flour bread more appealing through the nutritional components contained in rice bran.…”

“…The rice properties that lead to rice flour with a fine and less damaged starch through pin milling under dry conditions have been investigated (Ashida et al 2009, Ashida 2014. The properties of rice flour bread made from high-yielding cultivars (Aoki et al 2010(Aoki et al , 2012 and the effects of water soaking on the breadmaking quality of brown rice flour (Hamada et al 2012) were also investigated, in order to ensure a stable supply of rice flour at a low price.…”

“…The production of brown rice flour will also contribute to reducing the cost of producing rice flour because no polishing processes are required (Hamada et al 2012). Brown rice provides more desirable nutritional properties and biofunctional components, such as inositol, dietary fiber, and gamma aminobutyric acid (GABA), as compared with white rice (Ohtsubo et al 2005).…”

“…However, the use of brown rice flour with wheat and/or gluten as an ingredient in bread making remains limited (Okadome et al 2007) due to tendency of preventing the dough to rise as compared with white rice flour. It was found that brown rice flour produced using a jet mill after soaking for more than 12 h allowed a better formulation of brown rice flour bread with SLV equivalent to that of bread made with white rice flour containing gluten (Hamada et al 2012).…”

Properties of Floury Rice Mutant and its Utilization for Rice Flour

“…The development of a new polishing process and exploration of superior floury mutant rice subject to less weight loss during polishing is needed in future. As for brown rice flour, a new milling method is being developed, and the resulting flour is reported to be suitable for making high-SLV rice bread 6 . It is interesting to see whether floury mutant rice can be adapted for use as 18 .…”