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Effects of hydrocolloids on rheological and optical properties of proso millet dough
Y. ZHANG (1), H. Motta Romero (1), D. Santra (2), D. Rose (2) (1) University of Nebraska-Lincoln, Lincoln, NE, U.S.A.; (2) Unversity of Nebraska-Lincoln, , U.S.A.; (3) Unversity of Nebraska-Lincoln, , NE, U.S.A..

Proso millet is recognized as a source of healthy carbohydrate due to low glycemic index, gluten-free, minerals and dietary fiber. It is becoming common ingredient of gluten-free diet for coeliac patients. However, commercial exploration on using whole proso millet flour is limited. The lack of gluten reduces the elastic characteristics of dough and hence it is a challenge to mimic the wheat dough properties by supplementing the formulation. The aim of this project was to study the rheological properties of proso millet (PM) dough containing different hydrocolloids that could be used to completely replace wheat flour. Rheological characteristics of PM dough with hydrocolloids including guar gum (GG), xanthan gum (XG) and sodium alginate (SA) at concentration of 0%, 1% and 2% (wet basis) and 37% moisture content were compared with the behavior of wheat dough using a controlled stress rheometer. Wheat dough showed higher apparent viscosity values than PM dough at all shear rates except for the zero-shear rate. An increase of apparent viscosity was observed by the addition of all three hydrocolloids. The largest improvement was achieved by 2% XG, reaching the same infinitive-shear viscosity of wheat dough. Wheat dough exhibited weak gel behavior, whereas PM formed a lumpy dough. SA and XG provoked the largest upward trend in both storage and loss moduli, resulting in increased dough consistency. The increase of SA and XG from 1% to 2% showed slight improvement on the viscoelastic behavior of millet dough. PM dough showed a lower lightness value and a higher yellowness value than wheat dough. Generally, the addition of hydrocolloids reduced the color difference between PM dough and wheat dough except for GG. SA showed the least color change, followed by XG. The capacity of hydrocolloids to improve the rheology and color of PM dough followed the order of XG>SA>GG.