Physicochemical properties of the waxy rice mutant and its application on gummy bread

• Main Authors: Yao-Chu Huang, 黃耀主
• Other Authors: Meng-I Kuo
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/78392832316776910710

碩士 === 輔仁大學 === 食品科學系 === 98 === Rice is the staple of Asian people’s diet. Diverse rice processed foods could be manufactured based on rice variety. Rice flour is recently used for making the gluten-free rice bread. The physicochemical properties of rice flour and starch are important indicators for evaluation its applications. Gummy bread is a novel and popular baking product. It possesses crisp crust and unique chewy crumb texture. The main ingredients of gummy bread are modified starch and water. However, the organic and nature products are highlighted presently in the consumer market. Therefore, formulating a nature-based ingredient for gummy bread is crucial for the producer. The objectives of this research were to study the physicochemical properties of rice flours and starches from Tainung 67 waxy rice mutants in different crop years, to evaluate the optimized condiction for gummy bread processing, and to investigate the effect of substitution of waxy mutant rice flours for modified starch on the microstructure and rheological properties of dough and the texture of gummy bread. The result showed that based on the length and grain shape of milled rice, the waxy rice mutants SA402 and SA486 were belonged to japonica rice and SA419 and SA512 were belonged to indica rice. The viscosity values of indica rice flour were higher than that of japonica rice flour. The physicochemical properties of rice mutants were affected by crop year. For gummy bread making, the critical stress of dough was decreased, but the volume, specific volume, and porosity of bread were increased with increasing the ratio of water in the formula. The microstructure analysis of dough revealed that increase or decrease the ratio of water in the formula resulted in the aggregation of the mixture of protein and lipid. This might affect the appearance and texture of gummy bread. Altering the mixing time of dough did not change the rheological properties and microstructure of dough and the texture of gummy bread significantly. The texture of gummy bread decreased with increasing the degree of rice flour subsititution. The texture of gummy bread made by SA419 was better than that of bread made by SA402 since the dough prepared with SA402 had more uneven distributed aggregates from the mixture of protein and lipid. In conclusion, rice mutant SA419 possesses unique physicochemical properties and could be used as ingredient for gummy bread making. Texture analyzer, confocal scanning laser microscopy, and dynamic rheometer were suitable for observing the texture of gummy bread and the microstructure and rheological property of dough. Those information could further be used for explaining the mechanism of gummy bread formation.