Effects of particle size of rice flour on flour characteristics and quality and in vitro digestibility of bread

Abstract

In this study, the impact of substituting three different particle sizes (75, 125 and 212μm) of Huong Lai rice flour on flour characteristics, bread quality and in-vitro starch hydrolysis was studied. Three different particle sizes of rice samples were obtained by milling rice granules and sieveing. Then, bread was made from wheat flour with or without supplementing with 20% of Huong Lai rice containing these different granulations. In terms of flour characteristics, while different particle size insignificantly afftected the flour composition, swelling power and viscosity, a considerable change (P<0.05) was recorded in water absorption index which increased as the reduction in particle size. Results of baking experiments showed that insignificant variations (P>0.05) in physical characteristics (loaf weight, loaf volume and specific volume), texture profile and sensory attributes of breads containing were influenced by partticle size when incorporating 20%. Regarding to nutritional aspects, particle size induced different patterns in starch enzymatic hydrolysis, with the finer fraction (75μm) showed significantly higher value of rapid digestible starch (RDS) and lower value of resistent starch (RS) than coarser fraction (212 μm), whereas no significant difference in the amount of slowly digestible starch (SDS). As a result, the study of the impacts of particle size of rice flour in cereal based foods is important and three particle size (75, 125 and 212 μm) are moderately acceptable in applying to make substituted bread without negative properties. Key words: different particle size, resistant starch, substituted bread, physical characteristics, textural profile, sensory attributes.