Optimization of extrusion process parameters for the antinutritional compositions of aerial Yam (Dioscorea bulbifera)-soybean (Glycine max) flour blends using response surface methodology

Enobong O Umoh; Madu O Iwe; Phillipa C Ojimelukwu

Optimization of extrusion process parameters for the antinutritional compositions of aerial Yam (Dioscorea bulbifera)-soybean (Glycine max) flour blends using response surface methodology

Authors
Enobong O Umoh, Madu O Iwe, Phillipa C Ojimelukwu

Abstract
A study on the optimization of extrusion process conditions for antinutritional factors of aerial yam-soybean flour blends was carried out, using a laboratory scale single-screw extruder with the flour blending ratio of 25% aerial yam: 75% soybean. Response surface methodology based on Box-Behken design at three factors, five levels of barrel temperature (95, 100, 105, 110, and115

), screw speed (85, 100, 115, 130, and145rpm) and feed moisture (31, 33, 35, 37, and 39%) were used in 20 runs. Adequate and significant (p< 0.05) regression models with high regression coefficient, R²

0.9 were obtained, showing that the models can be used to navigate the design space. Results obtained showed that the anti-nutritional factors of the extrudates ranged between 0.79

0.002 and 5.11

0.008/100g hydrogencyanide (HCN), 12.48

0.025and 32.86

mg/100g phytates; 0.93

0.026 and 5.46

0.009/100g tannins; 45.81

0.024 and 102.71

1.244/100g oxalates. Analysis of variance showed that barrel temperature, screw speed and feed moisture significantly (p< 0.05) affected the HCN, phytates, tannins and oxalates content of the extrudates. Optimization results based on desirability concept indicated that a barrel temperature of 112.83

, screw speed of 127.87rpm and feed moisture of 32.59% would produce extrudates of preferable anti-nutritional factors.

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