REACTIVE EXTRUSION OF BEAN FLOURS

Bean flour possesses a significant fraction of water-insoluble components that are known to limit its uses in food applications. This study aimed to determine if using specific enzymes targeting the dietary fiber of bean flour could increase solubility, release protein and starch, and improve its utilization as a replacement for soy protein isolates in meat analogues. Water solubility, protein solubility, starch content and texture of bean flour was measured after enzymatic treatment with pectin- or hemicellulose-degrading enzymes in aqueous suspension. Low moisture reactive extrusion trials ranged from 60-80% solid content at 2 % enzyme content. High moisture extrusion ranged from 30% solid content from 1.5 to 5% enzyme content and from 40 % solid content at 2% enzyme content. Water solubility and insoluble protein increased with both low and high moisture reactive extrusion. Starch content increased with high moisture reactive extrusion. Beta-glucanase increased starch and insoluble protein content more than polygalacturonase treatments. However, Polygalacturonase and beta-glucanase increased overall water-solubility similarly. Determined starch content decreased with low moisture extrusion and both enzymes behaved equally. In the final set of trials, meat analogues were prepared with wheat gluten in combination with soy protein isolate, bean flour, or a mixture of soy protein isolate and bean flour. Replacing soy protein isolate with bean flour in meat analogues provided comparable hardness and anisotropic index. Polygalacturonase and beta-glucanase treatments during reactive extrusion of bean flours both decreased hardness of bean-containing meat analogues; beta-glucanase decreased the anisotropic index, whereas analogues made from polygalacturonase-treated flour did not differ from the control. Therefore, reactive extrusion showed either negative or null impact on texture. Reactive extrusion with polygalacturonase and beta-glucanase improved some desired analytical targets for bean flours, but the practical application (meat analogue) did not demonstrate an improvement.