PROCESS OPTIMIZATION WITH RESPECT TO THE EXPANSION RATIOS OF MILLET‐ AND LEGUME (PIGEON PEA)‐BASED EXTRUDED SNACKS

Abstract

ABSTRACT Extruded snacks were made from five blends of millet and legume at varying moisture content (12, 15, 18, 21 and 24%, wet basis [wb]). The percent of legume in the blends were, 12, 16, 20, 24 and 28. Designed experiments were conducted based on central composite rotatable design to determine the optimum processing condition with respect to the expansion ratios of the extrudates. A single‐screw laboratory Brabender DA47055 (Duisburg, Germany) extruder was operated at different die head temperatures (160–200C), barrel temperatures (100–140C) and screw speeds (100–140 rpm). The optimum processing conditions obtained using response surface methodology were: moisture content – 19%, wb; blend ratio – 15.7% legume; die head temperature – 190C; barrel temperature – 136.5C and screw speed – 140 rpm. The corresponding expansion ratios viz. specific length,sectional expansion index, longitudinal expansion index and volumetric expansion index were 64.3, 5.5, 0.6 and 3.3, respectively. PRACTICAL APPLICATIONSExpansion ratios are a good means to estimate the texturization caused because of the starch in the extruded products. The findings of the present research work can be used to relate the operating variables of extruder with the expansion ratios of the extrudates. The limitations of soil and irrigation facility in the developing countries compel the farmers to grow hardy crops like millets. Legume flour for the snack can be made out of the brokens (a by‐product of legume milling) formed from the legume mills. The snack thus made shall benefit the farmers as well as the mill owners. Moreover, the consumption of a highly nutritive snack, rich in fiber (millet) and protein (legumes) would help meet the nutritional requirements of the consumers.