Optimization of process variables for the preparation of expanded finger millet using response surface methodology

Abstract

The decorticated finger millet was subjected to high temperature short time treatment to prepare expanded millet, a ready-to-eat new generation product. It was observed that, flattening the grains to the desired shape factor and the moisture content were critical factors for obtaining the millet with maximum expansion ratio. Accordingly, the effect of moisture content of the millet prior to flattening, the shape factor and drying time and their complex interaction on the expansion ratio of the millet were determined. Besides, the bulk density, sphericity, hardness and overall acceptability of the expanded millet were also evaluated using a central composite rotatable experimental design. Based on the design, the optimal conditions for obtaining fully expanded millet were, moisture content of about 40% prior to flattening, shape factor ranging from 0.52 to 0.58 and drying time varying from 136 to 150 min. The product prepared under these conditions had an expansion ratio ( Y 1) ⩾ 4.6, bulk density ( Y 2) ⩽ 0.17 g/cm 3, sphericity ( Y 3) ⩾ 0.90, hardness/texture ( Y 4) ⩽ 5.0 N and the overall acceptability ( Y 5) ⩾ 7.2.