Response Surface Modelling of Effects of Extrusion Conditions on Some Anti-Nutritional Composition of Water Yam Based Noodles Analogue

Abstract

A second order central composite response surface methodology was used to investigate the effect of extrusion process on anti-nutritional factors of noodles analogue from water yam, yellow maize, and African yam bean. Flour samples were blended in the ratio of 60% water yam, 10% yellow maize, and 30% African yam bean based on preliminary result. The flour produced was used to extrude noodles analogue using a brabender single screw laboratory extruder (Duisburg DCE 330 model) fitted with 3.0mm die nozzle diameter. A central composite rotatable design (CCRD with three variables, namely barrel temperature, feed moisture content and screw speed and five level coded – a, -1, 0, +1, +a, was used and data analyzed by regression analysis. Results showed that phytate ranged from 0.02 to 0.10g; trypsin inhibitor ranged from 0.003 to 0.39% and tannin content ranged from 0.25 to 1.02%. The anti-nutritional composition of the noodles analogue was all at a safe level. The coefficient of determinations (R2) was high and ranged from 0.9014 to 0.9522 at 5% levels. The response surface plots suggested that the models developed had a good fit and the CCRD was effective in explaining the effect of the process conditions on noodles analogue as influenced by barrel temperature, feed moisture content, and screw speed of the extruder. The data obtained from the study could be used for control of product characteristics. The study indicated that improved noodles analogue from available and cheap roots, cereal and legumes such as water yam, yellow maize and African yam bean with safe anti-nutritional factors can be produced for possible projection for the commercial production of noodles analogue.