Evaluating the effects of amylose and Concord grape extract powder substitution on physicochemical properties of wheat flour extrudates produced at different temperatures

Abstract

In this study, the effects of Concord grape extract powder (CGEP), high-amylose starch, and their combinations on quality parameters of extruded products were investigated by substituting wheat flour with those ingredients in the formulations. Physical quality parameters such as water absorption, bulk density, diametric expansion and hardness of extrudates were evaluated in addition to thermal properties, pasting properties and resistant starch contents. Average values obtained for 90, 120 and 150 °C extrusion temperatures changed respectively as follows: 0.916, 0.987 and 0.467 N for hardness; 2.12, 4.07 and 5.12 ml water/g sample for water absorption; 1.35, 2.09 and 2.51 for diametric expansions and 1286.6, 723.6 and 311.1 kg/m(3) for bulk densities. Extrusion temperature was found to have more distinct effect on physical quality parameters of extrudates than the substitution level of ingredients. Both CGEP and amylose additions negatively affected pasting properties, slightly affected resistant starch content and prevented gelatinization. However retardation of retrogradation was more evident when substitution was with CGEP alone rather than its combination with amylose.

Keywords: Amylose; Anthocyanin; Extrusion; Grape; Wheat flour.