Cereal Chem. 91(2):146-151The effects of blending rice flour with wheat flour on bread texture and staling were investigated with three rice varieties with different amylose contents. For the texture analysis of bread crumb, the compression test, puncture test, and tensile test were performed. A flour blend containing rice flour suppressed the recovery of the crumb after compression. For the puncture test, blends with rice flour increased the distance to penetrate the crumb. The rupture strain measured with the puncture test decreased with staling of the bread crumb for all samples tested. The fresh bread crumb sample containing waxy rice flour had much greater extensibility in the tensile test than the other samples tested, but it was dramatically decreased after one day of storage. Endothermic enthalpies corresponding to retrograded amylopectin, which is part of the staling process, were also measured. The enthalpy of bread crumb from the blended flour was lower than that of wheat flour bread up to three days but was higher on day 4. A blend of rice flour thus reduced amylopectin retrogradation during early storage, but it was accelerated later. Bread blended with waxy rice flour showed the lowest enthalpy during storage.
Cooked rice bread was made with cooked rice substituted for 0 to 30% of the wheat flour. Eleven rice cultivars were used to clarify the effects of rice properties on specific loaf volume (SLV). The cooked rice bread had higher SLV than the bread without substitution, except for bread made with rice having highamylose content. The maximum specific loaf volume (Max SLV) of cooked rice bread was calculated using SLV loaf volumes. Max SLV was negatively correlated with amylose content and rice hardness, while rice stickiness factors were positively correlated with Max SLV. Because amylose content affects rice hardness and stickiness, amylose content appears to play a key role on SLV. Most of the popular rice cultivars in Japan are sticky and soft, with intermediate amylose content, and yields cooked rice bread with high volume.Keywords: bread, cooked rice, amylose, specific loaf volume, rice property *To whom correspondence should be addressed. E-mail: tomoyaok@affrc.go.jp IntroductionRice is a staple food in Japan. However, rice consumption by Japanese has decreased in recent years, and this is becoming an economic problem (Ministry of Agriculture, Forestry and Fisheries, 2007). The development of processed food made with rice flour is reportedly expanding rice consumption (Yoza et al., 2008). On the other hand, many Japanese tend to eat bread for breakfast and lunch as a result of the introduction of European and American eating habits. The Japanese government has recommended the introduction of rice flour bread for school lunches in elementary and junior high schools in order to expand the consumption of rice. Bread making with rice flour has therefore developed and has been widely reported a,b, Araki et al., 2009.However, rice flour bread does not rise as much as wheat flour bread (Ogawa et al., 2003, Yamauchi et al., 2004. Ordinary rice flour bread has a lower volume than wheat flour bread, as the glutenin and gliadin necessary for the gluten net in the bread structure are not present in rice. Most rice flour bread is therefore made with gluten powder and other additives in order to improve bread volume, but gluten powder is often produced from imported wheat, and this is unsuitable for improving Japanese food self-sufficiency.Many researchers have made efforts to produce essential structures using compounds other than gluten in non-wheat bread (Moore et al., 2006, Gallagher et al., 2004. Hydrocolloids such as hydroxy propyl methylcellulose (HPMC) yield non-wheat flour bread with good volume (Cato et al., 2004, Lazaridou et al., 2007. Gujral used cyclodexitrinase or glucose oxidase to improve the quality of rice bread (Gurjal et al., 2003(Gurjal et al., , 2004, while Takahashi treated rice grains with hydrolytic enzymes (Takahashi et al., 2009). Although these methods were effective for producing rice bread, they require specialized equipment and are associated with high financial cost.We previously reported a method for making bread with Koshihikari cooked rice substituted for part of the wheat flour (Ok...
A dough swelling method to evaluate the utility of various rice flours for bread making was developed. Flour samples (2. 5 g) were evaluated for degree of dough rising during fermentation in plastic tubes. A swelling rate B 0. 7 could distinguish flour samples containing B 1 % gluten, indicating greater sensitivity than with the ordinary bread making method. This method can be utilized for bread quality evaluation of genetically modified rice.
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