AACC International - 2010 Meeting Abstract - Effect of extruder screw speed on physical and chemical characteristics and in vitro starch hydrolysis of pinto, navy, red and black bean extrudates

Meeting Abstract - Oral Presentation

Effect of extruder screw speed on physical and chemical characteristics and in vitro starch hydrolysis of pinto, navy, red and black bean extrudates
C. SIMONS (1), C. Hall (1), M. Tulbek (2)
(1) North Dakota State University, Fargo, ND, U.S.A.; (2) Northern Crops Institute, Fargo, ND, U.S.A.
Cereal Foods World 55:A31

Commercial precooked pinto, navy, red and black bean flours were extruded at different screw speeds (320, 380 and 440 rpm) using a twin screw extruder. Effect of speed on physical and chemical characteristics and in vitro starch hydrolysis was investigated. Data was analyzed using one way ANOVA (P < 0.05) in a completely randomized design on each type of bean with extrusion speed being the independent variable. Moisture retention decreased significantly in black beans at 440 rpm but was not significant in extrudates of navy, pinto and red beans. Water activity decreased significantly in extrudates made at 440 rpm for all beans, except navy. Expansion index decreased at higher speeds, with significant difference at 440 rpm for all beans. Color changes on hunter color scale were not significantly different for extrudates made from black, pinto and red beans, but navy bean extrudates had increased b value with increasing rpm. Texture hardness values decreased at higher speeds, except for navy bean which was not significantly affected. Significant reduction in hardness was observed for black and pinto bean extrudates extruded at 380 and 440 rpm. Hardness in red bean extrudates processed at 440 rpm was significantly lower than at other speeds. Water absorbance index and water solubility index were not significantly affected by screw speed. In addition, extrusion speed had no significant effect on resistant starch in extruded beans. Resistant starch in pre-cooked flour however, was significantly higher than extrudates of the four beans. Resistant starch ranged from 3.65–4.83% d.b. in extrudates, and 5.02–5.78% d.b. in pre-cooked bean flours. Details of these results will be presented, in addition to effect on glycemic index. Data obtained will provide useful information in selecting an appropriate extrusion speed to produce low glycemic index bean snacks.