EFFECTS OF SOME BAKING INGREDIENTS ON PHYSICAL AND STRUCTURAL-PROPERTIES OF WHEAT-FLOUR EXTRUDATES

The effects of six baking ingredients (sucrose, nonfat dry milk, whole egg powder, shortening powder, glyceryl monostearate [GMS], sodium bicarbonate) on expansion, bulk density, breaking strength, and cell structure of wheat flour extrudates were studied. A Wenger TX52 twin-screw extruder was used to prepare extrudate samples. A one-half fractional 2(6) factorial experimental design was used to determine the effects of each baking ingredient on wheat flour processed under fixed extrusion conditions. Feed moisture content was 31%, barrel temperature before the die was 130-degrees-C, and screw speed was 400 rpm. Extrudate expansion was characterized by sectional, longitudinal, and volumetric expansion indexes (SEI, LEI, and VEI, respectively). Cell structure was analyzed with a scanning electron microscope and by counting the number of cells per unit area. The SEI and LEI were significantly affected by both sucrose and GMS (P < 0.01). The interaction of shortening powder and GMS had significant effects on the LEI (P < 0.01), and a sucrose-egg interaction affected the SEI (P < 0.05). Bulk density was significantly affected by sucrose, shortening powder, and GMS (P < 0.05). Sucrose and shortening powder had significant effects on breaking strength and cell structure.