Scanning electron microscopic observations of dough and bread supplemented with Gastrodia elata Blume powder

Dough and bread prepared from wheat flour containing varying amounts of added Gastrodia elata Blume (GEB) rhizome powder [0, 0.5, 1.0, 1.5, and 2.0% (w/w)] were examined by scanning electron microscopy (SEM) during fermentation and baking. The structure of the doughs containing added GEB was found to be related to the protein matrix. Further, it was found that large starch granules and strings of small starch granules play an important role in dough structure. The control dough (no added GEB) had a membrane-like structure, and doughs with 0.5-1.0% added GEB had membrane-like structures that were more developed than those of the control, resulting in increased bread volumes. At 1.5-2.0% GEB levels, however, the doughs tended to have mesh-like structures and result in decreased bread volumes. The dough samples with 0.5 and 1.0% added GEB powder had well-developed gluten matrices with evenly dispersed starch granules. These samples resulted in breads with numerous gas bubble eruptions on their surfaces and consequently in larger loaf volumes than were obtained at other levels of GEB. After the second fermentation, many expanded starch granules were observed and these starch granules were dispersed more evenly than after the first fermentation. In 0.5-1.0% GEB bread, many of the large starch granules had expanded after fermentation, but small starch granules had not. The data obtained in this study suggest that bread baked with 0.5-1.0% GEB exhibits a better loaf volume due to the more complete development of a gluten matrix.