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In Vitro Bile Acid Binding Capacity of Milled Wheat Bran and Milled Extruded Wheat Bran at Five Specific Mechanical Energy Levels

¹Western Regional Research Center, USDA, Agricultural Research Service, 800 Buchanan Street, Albany, CA 94710. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ²Corresponding author. Phone: 510/559-5665. Fax: 510/559-5777. E-mail: tsk@pw.usda.gov

The in vitro binding of bile acids of milled wheat bran (MWB) and milled extruded wheat bran (MEB) at five specific mechanical energy (SME) levels of 120 (MEB-120), 177 (MEB-177), 234 (MEB-234), 291 (MEB-291), and 358 (MEB-358) Whr/kg on a fat-free dry weight basis was determined using a mixture of bile acids secreted in human bile at duodenal physiological pH 6.3. Relative to cholestyramine (bile acid binding, cholesterol lowering drug) in vitro bile acid binding capacity on dry matter, total dietary fiber (TDF), and insoluble dietary fiber (IDF) basis was for MWB: 21, 43, 45%; the range for MEB was 18–21%, 34–41%, and 36–43%, respectively. MWB resulted in significantly higher bile acid binding than that of MEB at 120, 234, and 291 Whr/kg on a dry matter, TDF, and IDF basis. These results demonstrate the relative health-promoting potential of MWB = MEB-177 = MEB-358 > MEB-120 = MEB-234 = MEB-291 as indicated by the bile acid binding on a dry matter basis. Data suggest that significant improvement in health-promoting (cholesterol-lowering and cancer-preventing) potential could be obtained in WB by milling (low-cost processing) the bran to finer particle sizes and extruding (high-cost technology). Milling WB to small particle size (weighted mean 0.508 mm) increased surface area, in addition it may have induced changes in the physical and chemical characteristics of WB or created new linkages, binding sites of the proteins, starches, and nonstarch polysaccharides, which significantly increased the bile acid binding ability of the MWB.