Effects of treated and untreated bran in dough dynamic rheology.

Grains of the wheat variety Tajan were milled into straight-run flour and bran. Proximate analysis, farinograph experiments and rheological characteristics were conducted. Two types of bran (hydrothermal treated and untreated) at three levels (0%, 5%, 10%) were added to the parent flour. Proximate analysis and farinograph experiments of these flours were conducted. The effects of adding treated and untreated bran in linear (strain=0.1%) and non-linear limits (strain=1%, 5%, 10%) have been determined by dynamic oscillatory tests. Results show that, in the linear limit, the G' value for the untreated bran sample is very close to parent flour while the G' value of treated bran flour is lower than that of parent flour. The same changes occur in G'' values. In the non-linear limit, the G' values for both treated and untreated bran samples were higher than parent flour while the G'' value for untreated bran samples had no significant difference from the parent flour. Tge loss tangent for untreated bran flour in the non-linear limit was higher than that of the parent flour, while for treated bran flour it is lower than parent flour. It can be concluded that untreated bran weakens the gluten matrix. On the other hand, adding treated bran, to some extent, strengthens the protein matrix.