K. B. Filli, I. Nkama, V. A. Jideani
American Journal of Food Science and Technology. 2013, 1(4), 87-101DOI:
Abstract: Studies were conducted on the Extrusion of fura from pearl millet and Bambara groundnut applying the Response Surface Methodology (RSM) consisting of 15 design points, using a single screw laboratory Brabendar extruder. The effects of three extrusion variables (feed composition – percentage Bambara groundnut to pearl millet, feed moisture content and screw speed) on some physical properties (bulk density, ‘BD’ expansion ratio, ‘ER’, mass flow rate, ‘MFR’, average residence time, ‘ART’ and specific mechanical energy, ‘SME’) and some functional properties (water absorption index, ‘WAI’, water solubility index, ‘WSI’ and viscosity); of fura extrudates were evaluated using response surface method (RSM). Models were developed and appropriate statistical analysis adopted to test the adequacy of the models. Linear, quadratic and interaction regression and coefficient terms and coefficients of determinants were computed to test the adequacy of the models and response surface plots were also produced from the equation and model. The linear, quadratic and interaction terms were significant (p<0.05) for ART and SME, however for MFR interaction term was not significant (p>0.05), however the linear and quadratic terms were significant (p<0.05). The error analysis showed that lack of fit was not significant (p<0.05) for ART. The regression models for data were significant (p<0.05) with satisfactory coefficients R2 of 0.87, 0.87 and 0.92 for ART, MFR and SME respectively indicating a good fit. The coefficients of variation (CV) were less than <10%. Extrusion conditions affected the ER significantly (p<0.05) by linear and interaction terms. The BD was influenced by only the linear term (p<0.05). The R2 were 0.82 and 0.84 for ER and BD respectively, suggesting good fit. Linear, quadratic and interaction terms affected WAI. However only linear and quadratic terms indicated influence on the WSI. The R2 were 0.93 and 0.84 for WAI and WSI respectively. The samples shows that, linear, quadratic and interaction terms influenced viscosity significantly (p<0.05) with the linear term showing more effect and the R2 was 0.88 for viscosity, The lysine content (result not shown) of extrudates tremendously increased as expected as a result of inclusion of Bambara groundnut. The essential amino acids (result not shown) were present in adequate levels if compared with the recommended values of FAO/WHO (1973).