Effect of Type of Hydrocolloid Coating and Soy Flour Addition on Physiochemical Properties of Donut

The effect of two types edible coatings, based on methylcellulose (MC) and gum tragacanth (GT) in combination with soy flour on physiochemical properties of fried donuts were studied. Dough was prepared with 0, 5 and 10% substitution of wheat flour with soy flour. Dough surface coated with hydrocolloid solutions (1% w/w) then fried at 150°C. Addition of soy flour did not show significant effect on moisture and oil content of the fried donut (P>0.05) but significantly (P<0.001) reduced the volume of the fried donuts. However, coating was effective method to reduction of oil content. Because of film forming properties, GT and MC coatings significantly (P < 0.05) reduced oil uptake but they did not have significant effect (P > 0.05) on moisture content and volume of the fried donut. Farinograph evaluation of dough showed that the addition of 10% soy flour considerably (P< 0.001) increased water absorption.