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The growing snacking habit and steady increasing demand for healthy snacks have drastically changed the ready-to-eat snack market in recent years. While the current healthy, ready-to-eat snack products are still dominated by whole cereal grains, legumes, especially dry edible beans, have a high potential to emerge in nutritional, novel food. Dry edible beans (Phaseolus Vulgaris L) are not only economically valuable but also nutritionally important, since they are important sources of proteins, B vitamins, mineral elements, and soluble dietary fibers even when compared to whole grain cereals. Recent studies have shown extrusion processing is not only effective at producing an acceptable ready-to-eat snack product but also in altering the in vitro digestibility (starch, protein, and mineral elements) of bean flour. The present thesis describes two research projects to improve the utilization of pinto bean by extrusion technology. The first study was conducted to investigate the effects of pinto bean flour and feed moisture on the physical properties and in vitro digestibility of rice-bean extrudates. Addition of bean flour adversely affected the physical properties of rice-bean extrudates, but was partially alleviated by decreasing feed moisture. Rapidly digestible starch (RDS) decreased and resistant starch increased with increasing bean flour and feed moisture. In vitro protein digestibility increased as feed moisture decreased. For the second study, the effects of extrusion parameters, namely barrel temperature (ᵒC), screw speed (rpm), and moisture content (%), on in vitro element bioaccessibility were investigated. Although extrusion parameters were found to not significantly affect the bioaccessibility of mineral elements, extrusion processing significantly increased the bioaccessibility of elements compared to flour. The average increase was higher for essential elements (Fe, Mg, P, and K) than for toxic elements (Cd and Pb) in the extruded product. The correlation analysis suggested that the increase of bioaccessible elements by extrusion was unique depending on the binding mechanism to chemical substances (phytic acid, tannins and dietary fiber components).
Advisor: Devin J. Rose