Development and characterization of physical stability, glycemic index, flow behaviors, and antioxidant activity of finger millet-based beverage

Millets are gaining attention as a superfood due to their higher nutritional value and cost-effectiveness. In this regard, extraction condition for the development of finger millet-based beverage was optimized using a central composite design. Soaking time (X1) and temperature (X2) in the range of 5-10 h and 40-60 degrees C, respectively, were the independent variables taken for three responses, namely, yield, total solids, and sedimentation index. The optimized conditions are best fitted in quadratic model (R2 0.91) for all the dependent variables. Accordingly, the optimized levels selected for soaking time and temperature were 10 h and 60 degrees C respectively, resulting in the yield (Y1) of 91.86% +/- 0.94%, total solids (Y2) of 17.72% +/- 0.56%, and sedimentation index (Y3) of 12.18% +/- 0.06%. Further, xanthan gum (0.5%) and jaggery powder (5%) were added in the optimized beverage to improve its physicochemical and functional properties. Xanthan gum improved the physical stability and rheological properties of the beverage, whereas jaggery improved the flavor and phenolic content of the same. The optimized beverage had a good amount of phenolic content (53.70 mu g GAE/mL), antioxidant activity (DPPH 13.76 mu mol/mL), zeta potential (-19.8 mV), and glycemic index (57). The flow curve of beverages was obtained using power law model, and result indicated good consistency index (k = 0.7716 Pa s) with flow behavior (n = 0.3411) depicted its pseudoplastic nature. The optimized extraction condition significantly reduced the antinutrients, tannin, and phytic content by 47% and 14%, respectively, in optimized beverage than control.