NAVY BEAN FLOUR FRACTIONS IN COMPOSITE DOUGHS - EFFECT OF BEAN GRADE ON RHEOLOGY PARAMETERS AND MICROSTRUCTURE OF WHEAT DOUGH

To increase the economic feasibility of producing dry-roasted, airclassified legume flour fractions for use in composite flours, the effect of using prime and cull navy beans to produce high protein flours (fines) and cotyledon flours was investigated. These flours were used to produce wheat flour-bean composite doughs (at ratios of 95:5 and 90:10) for farinograph and low-temperature scanning electron microscopic microstructural evaluation. Composite flours with increased protein exhibited the expected increase in absorption, delay in arrival and peak time, and reduction in stability. An exception to this was the composite flour containing 5% prime navy bean fines. The stabilities of composites containing high protein fines were greater than those containing cotyledon flour. Bean grade produced few significant differences in farinograph parameters. For composites with 10% cull fines, absorption was higher, whereas arrival and peak times were significantly shorter. Microstructures of wheat-bean flour blend evaluations differed from those of the control (100% flour) for all variables. No differences in farinograph parameters due to bean grade were found for any composites containing cotyledon flour. The microstructure of composites with cotyledon flour from cull beans showed slightly greater gluten disruption than was evident in the doughs from the wheat-prime cotyledon composites.