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Factors Affecting Viscosity of Slurries of Oat Groat Flours

¹Graduate assistant and associate professor, respectively, Department of Cereal Science, Harris Hall, North Dakota State University, Fargo, ND 58105. ²Current address: Kellogg Company, Science and Technology Center, 235 Porter Street, Battle Creek, MI 49016. ³Research chemist, USDA-ARS Hard Red Spring and Durum Wheat Quality Laboratory, Harris Hall, North Dakota State University, Fargo, ND 58105. Mention of trademark or proprietary products does not constitute a guarantee or warranty by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable. ⁴Corresponding author. E-mail: DOEHLERT@PLAINS.NODAK.EDU

Oat grain is routinely kilned and steamed before milling to develop flavor and to inactivate lipid-degrading enzymes. Heat treatments can significantly affect viscous properties, which have functional and nutritional importance. Oat flour slurries (23%, w/w, solids dry basis) made from steamed (for 20 min) or autoclaved (at 121°C, 15 psi, for 10 min) grain developed high viscosities, whereas flour slurries made from raw or kilned (105°C for 90 min) oats did not. Flour slurries made from raw groats, surface-sterilized by 1% hypochlorite, were more viscous than untreated raw groat flour slurries, suggesting that β-glucan hydrolases on the surface of the groat caused the viscosity losses observed in raw or kilned groats. However, because viscosities developed by surface-sterilized groats were not as great as in steamed oat-flour slurries and because some roasting treatments also inactivated enzymes without enhancing viscosity, it appears steaming might also affect the β-glucan polymer, resulting in its greater hydration in solution. Smaller particle size and higher incubation temperature also resulted in increased flour slurry viscosity, presumably because of increased hydration of the β-glucan. Rmoval of lipids from steamed oat flour significantly increased the oat flour slurry viscosity, apparently by increasing the β-glucan concentration in the flour.