Nitrogen solubility index and amino acid profile of extruded African breadfruit (T. africana) blends
were thoroughly mixed in a Hobart_-mixer at three variable, with the following combinations 40:5:55, 55:5:40, 70:5:25, 85:5:10 and 100:0:0% for African breadfruit, corn and soybean, respectively. These combinations were hydrated to moisture contents of 15, 18, 21, 24, and 27% and extruded at screw speed of 100, 120, 140, 160 and ISOrpm in a Brabender laboratory single-screw extruder. Effects of extrusion cooking and process variable conditions on nitrogen solubility index and amino acid profile were investigated. Nitrogen solubility index decreased with extrusion cooking by more than 50% in all the point blends. Soybean lowered nitrogen solubility index while African breadfruit increased it from 17 to 22% in the raw and 7.25 to 9% in the extruded samples. The model developed in the study accounted for 60.21% of the total variation in nitrogen solubility index and significantly (p<0.05) fitted. Feed moisture had significant (p<0.05) linear effect on nitrogen solubility index and a significant (p<0.05) cross product effect on interaction with screw speed. Retention of amino acid originally present in the raw was high ranging from 79 to 84%, indicating that process variable conditions were adequate and that blending African breadfruit with corn and defatted soybean before extrusion cooking has great nutritional benefit.
Keywords: African breadfruit; (T. africana) ; amino acids; extrusion, nitrogen solubility index
Nigerian Food Journal Vol. 25 (1) 2007: pp. 23-35
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