Optimization of physical properties and protein to produce functional extruded snack concocted with composite flour using RSM

Abstract

Currently, snack market is predominantly fat and calorie rich and deficient in nutrition, thus selling obesity, aiming children in particular. To counter this subject palatably, an effort was ventured by implementing extrusion cooking for designing a crisp snack by utilizing adjoined benefits of sweet potato flour (SPF; high carotene), rennet casein (RC; milk protein), barley flour (BF; fibre source) and rice flour (RF), as ingredients. The ingredient levels; treated as factors; were modulated using Central Composite Rotatable Design model with Response Surface Methodology approach. The level selection, rested on the model, was drawn from the fed range of 20 – 35 SPF, 15 – 30 BF, 10 – 30 RC and 30 – 40 RF; all being in parts. The recorded responses against the independent variables were bulk density, expansion index, hardness and protein. Polynomial equations and regression coefficients were obtained for each factor. The analyses by StatEase DesignExpert^TM software, v7.0, revealed statistically prominent positive and negative significances and non-significant effects of each independent variable over individual responses thru linear, interaction and quadratic levels at either p<0.01, p<0.05 or p>0.05. Maximization of protein was accounted for optimization criteria whilst rest responses were kept in-range. One out of three obtained optimized formulations was subjected to reproducibility validation (SPF 20, BF 15, RF 40 and RC 30 parts), leveling the selection on highest desirability quotient. A fairly palatable extruded snack was developed returning non-significant variance (p<0.01) over predicted scores. The optimized product had bulk density 0.098 g/cm³, expansion index 3.34, hardness 21.32 N and protein 27.5%.