Effect of process variables on trypsin inhibitor activity (TIA), phytic acid and tannin content of extruded African breadfruit–corn–soy mixtures: A response surface analysis

Flour samples of African breadfruit, corn and defatted soybean were extruded in a Brabender single-screw extruder (DCE 330, New Jersey). Effects of process variables on trypsin inhibitor activity (TIA) and other antinutritional factors (ANFs) were verified by response surface analysis (RSA). Blending improved the protein content of the mixtures but increased the ANFs. Extrusion cooking drastically reduced TIA, phytic acid and tannin content of the extrudates by 91%, 44% and 92%, respectively. The model developed produced the highest percent variation in TIA (80%) in comparison with either phytic acid (60%) or tannin (50%). Feed composition and screw speed were the most significant (P⩽0.05P⩽0.05) process variables affecting TIA. Effect of feed composition was quadratic, while that of screw speed was linear. The quadratic effects of screw speed and feed composition on tannin and phytic acid were also significant (P⩽0.05P⩽0.05).