Quality Improvement Study on Wheat Flour and Rice Flour Blended Bread with the Addition of Acid-soluble Wheat Protein

Abstract

The purpose of this study was to analyze the properties of wheat flour and rice flour that are used in the production of wheat flour and rice flour blended bread with the addition of acid-soluble wheat protein (ASP), and to examine the optimal additional amounts of sugars and enzymes that can improve the quality of the wheat flour and rice flour blended bread. In the sponge and dough method of bread-making, rice flour was used to replace 40% of the wheat flour, and 10% wheat protein (gluten and ASP) was added to the wheat flour and rice flour. Results of flour analysis confirmed that the rice flour (rice flour for bread and high amylose rice flour) had less damaged starch content than the wheat flour. Also, rice flour particles were smaller than wheat flour particles, and each displayed different viscosity characteristics. In wheat flour and rice flour blended bread, the addition of rice flour, with its low damaged starch content, decreased the amount of maltose produced during the fermentation of the sponge dough when compared to bread made with wheat flour only. Accordingly, the measured amount of gas generated during sponge dough fermentation also decreased. Therefore, when rice flour was used to replace 40% of the wheat flour, 2% maltose was added to the sponge dough to increase the gas amount and improve fermentability. When wheat flour and rice flour blended bread was made in which 40% of the wheat flour was replaced with rice flour, in comparison to the use of rice flour for bread, the use of high amylose rice flour resulted in a higher specific volume, and caving did not occur. When using two α-amylases with different optimum temperatures (50ppm each), it was possible to improve the specific volume of the bread and suppress the degradation of crumb firmness over time. Furthermore, the addition of 150ppm of lipase was effective at preventing the bread from caving, indicating that the addition of appropriate amounts of these enzymes improved the quality of wheat flour and rice flour blended bread.