Effect of morphology of mechanically developed wheat flour and water on starch from gluten separation using cold ethanol displacement

The mechanical development of wheat flour and water creates micro and macro structures in dough or batter that critically influence the ability to sep arate starch from protein by fluid displacement. This study sought to ident ify specific structural and rheological features and to relate these to sep aration as indexed by the separation factor. Structural features, especiall y protein and starch distributions, were examined using visible light micro scopy applied to dough samples that had been exposed to a protein dye. Flou r and water samples were developed in a Brabender microfarinograph at condi tions (water content and time of development) generally suitable for use of the USDA Western Regional Research Center, cold-ethanol fluid-displacement method. No truly homogenous structures were observed. However, distinct se gregation of protein and starch were apparent at all conditions. Structural features correlated qualitatively with the success of separation indexed b y the overall separation factor (alpha(p/s)) for the separation process. Hi ghly segregated states characterized by large protein bands, clustered star ch, and large open spaces were obtained with intermediate development (25 /- 5 min) and were most readily separated (cbs = 118 +/- 7). Segregated sta tes with relatively thin protein bands (less than or equal to 10 mu m dia) in complex networks entrapping starch were obtained after additional develo pment (less than or equal to 45 min) and were less completely separable (al pha(p/s) = 32 +/- 2). Segregated states with irregularly organized protein in the form of clumps and bands were obtained with minimal development and were partially separable (alpha(p/s) = 65 +/- 4). Consistency indicated on the microfarinograph increases monotonically throughout and beyond the peri od of maximum separability. However, elasticity changes and a high rate of increase in consistency evident in the microfarinogram may reflect changes in the structure that also reduce separability. The study demonstrated the use of the ethanol method to isolate development from displacement phenomen a for independent study.