| Abstract
| - The objective of this work was to evaluate extrusion cooking as a means to improve the nutritionalproperties of Phaseolus vulgaris L. that had been stored either at 42 °C and 80% relative humidityfor 6 weeks or for periods >1 year in cereal stores in tropical conditions. Storage under theseconditions resulted in an increase in cooking time increased (7.7- and 12-fold, respectively) as aresult of development of the hard-to-cook (HTC) defect. Single-screw extrusion of the milled beanswas carried out at four barrel temperatures and two moisture contents. The extrudate bulk densityand water solubility index decreased with increasing temperature, whereas the water absorptionindex increased due to the higher proportion of gelatinized starch in the extruded samples. Bothfresh and HTC beans contained nutritionally significant amounts of lectins, trypsin, and α-amylaseinhibitors, which were mostly inactivated by extrusion. Extrusion also caused a considerableredistribution of insoluble dietary fiber to soluble, although the total dietary fiber content was notaffected. Changes in solubility involved pectic polysaccharides, arabinose and uronic acids beingthe main sugars involved. Stored beans subjected to extrusion cooking showed physical and chemicalcharacteristics similar to those of extrudates from fresh beans. Keywords: Extrusion cooking; hard-to-cook beans; physical properties; antinutrients; dietary fiber
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