Effects of Extrusion Processing on the Proximate Compositions of Aerial Yam (Dioscorea bulbifera)-soybean (Glycine max) Flour Blends Using Response Surface Methodology

  •  Enobong O. Umoh    
  •  Madu O. Iwe    


The impact of extrusion process parameters on the proximate compositions of aerial yam (Dioscorea bulbifera)-soybean (Glycine max) flour blends was investigated with the help of a laboratory scale single-screw extruder, and 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 describing the effects of process parameters on the product quality attributes 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 proximate compositions ranged between 4.03± 0.002 and 5.90± 0.002% ash; 3.10± 0.001 and 7.02± 0.003% moisture content; 2.70± 0.001 and 4.67± 0.003% fibre; 24.57± 0.078 and 36.79± 0.004% protein; 11.39± 0.004 and 35.35± 0.011% lipid. The best extrusion condition combinations were 1150C barrel temperature, 115rpm screw speed and 35% feed moisture for ash content; 1000C barrel temperature, 130rpm screw speed and 33% feed moisture for moisture content; 1150C barrel temperature, 115rpm screw speed and 35% feed moisture for fibre content; 1050C barrel temperature, 145rpm screw speed and 35% feed moisture for protein content; 1050C barrel temperature, 85rpm screw speed and 35% feed moisture for lipids. Analysis of variance showed that only barrel temperature affected the ash composition significantly (p< 0.05). Barrel temperature, screw speed and feed moisture showed insignificant (p> 0.05) effect on moisture content, while fibre content was significantly (p< 0.05) affected by barrel temperature and screw speed. Protein and crude fat (lipid) contents were significantly (p< 0.05) affected by barrel temperature, screw speed and feed moisture.

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  • ISSN(Print): 1927-0887
  • ISSN(Online): 1927-0895
  • Started: 2012
  • Frequency: bimonthly

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