Development of a Quantification Method of the Gluten Matrix in Bread Dough by Fluorescence Microscopy and Image Analysis

The gluten matrix in bread dough develops through the mixing process, and its microstructure is known to greatly affect the quality of the end product. In this study, a novel method to quantify the gluten matrix was developed by applying image analysis methods used in the area of bone histomorphometry to fluorescence images of dough. Acquisition of clear images of the gluten matrix and the incorporated starch has been made possible by a novel fluorescence visualization method using acid magenta and the blue fluorescent filter. The images with high contrast between gluten, starch, and other constituents allowed accurate binarization between gluten and background. Bread dough at four mixing stages was made to observe gluten development. Three parameters were extracted from the gluten area: gluten thickness, total length of gluten per area, and average length of gluten. At the final (optimum) mixing stage, gluten thickness and average length of gluten showed minimum values, while the total length of gluten showed the maximum value. This showed that at the final mixing stage, gluten strands become thin and highly branched. In addition, thin membrane-like structures were observed at the over-mixing stage, indicating the breakdown of gluten structure. Further application of this quantification method to flours with different gluten content would enable comprehensive understanding of the gluten formation in dough.