Response surface analysis and process optimization of twin screw extrusion of apple pomace blended snacks

Abstract

Optimization of the extrusion process for apple pomace blended snacks was done using RSM. A blend of apple pomace, maize and soy flour was extruded at five levels of moisture content (12.6–19.4%), barrel temperature (116–184oC) and screw speed (232–568 rpm). The effects of these variables on product responses, viz. bulk density, expansion ration, colour, water absorption index, water solubility index, crispiness, sensory score of overall acceptance, and specific mechanical energy were determined and analyzed. Feed moisture had significant effect on all product responses, whereas screw speed and barrel temperature, both had significant effect on SME, ER and crispiness of the product. The response surface models fitted to all responses were highly significant, and had adequate precision more than 12 (>4 desirable), without having any lack of fit. Optimized extrusion parameters for preparation of quality snacks were 14% moisture, 130oC barrel temperature and 300 rpm screw speed.