Scanning electron microscopic observation of expanded structure of Yakifu supplemented with different starches

Basic Studies on the Production of Yakifu Part VII

Abstract

Contributions of different starches exhibiting different effects on the expansion of yakifu and having different physicochemical characteristics were studied to expanded structure construction of yakifu. Granular starches inhibited sequential, fibrous and sheet structure formation of gluten, resulting in network structure in gluten dough during kneading, while amorphous starch didn't. Pregelatinized and soluble starch with higher swelling power interfered with homogeneous mixing of gluten and starch. Well expanded products contained well arranged air cells from bottom to top, but only poor air cells were formed in inferior products. In expanded products of synthesized flour with high amylose corn starch or mung bean starch, starch granules were observed on the air cell walls. Isolated starches from the expanded products showed polarizing cross, indicating parts of those starches were resistant to the baking temperature. At the beginning of expansion, expanded glutenous structure was covered with pasted starch to form closed individual air cell. These air cells were accumulated to give bigger specific volumes. With an increase in the proportion of gelatinized starch in the flour, the specific volume was lowered. Therefore, it was concluded that granular starches with appropriate swelling power which gelatinized during baking contribute the expansion of yakifu.