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Fermentability of Oat and Wheat Fractions Enriched in β-Glucan Using Human Fecal Inoculation

¹Agriculture and Agri-Food Canada, Food Research Program, 93 Stone Rd. West, Guelph, N1G 5C9, ON, Canada. ²Corresponding author. Contribution S076 of Food Research Program and 11747 of Eastern Cereal and Oilseed Research Centre. ³Swiss Federal Institute of Technology, Institute of Food Science, ETH Zentrum, CH-8092 Zurich, Switzerland. ⁴Agriculture and Agri-Food Canada, Eastern Cereal and Oilseed Research Centre, Ottawa, K1A 0C6, ON, Canada.

Fermentation by human fecal bacteria of fractions of wheat bran prepared by preprocessing technology were examined and compared with a β-glucan-rich oat bran and a purified β-glucan (OG). The wheat fractions were essentially a beeswing bran (WBA), mainly insoluble dietary fiber, and an aleurone-rich fraction (WBB) containing more soluble fiber and some β-glucan (2.7%). The oat bran (OB) had more endosperm and was very rich in β-glucan (21.8%). Predigestion of WBB and OB to mimic the upper gastrointestinal (GI) tract gave digested wheat bran fraction B (WBBD) and digested oat bran (OBD), respectively. These predigested fractions were fermented in a batch technique using fresh human feces under anaerobic conditions. Changes in pH, total gas and hydrogen production, short chain fatty acids (SCFA), and both soluble and insoluble β-glucan and other polysaccharide components, as determined from analysis of monosaccharide residues, were monitored. Fractions showed increasing fermentation in the order WBA < WBBD < OBD < OG. Variations in SCFA production indicated that microbial growth and metabolism were different for each substrate. Polysaccharide present in the supernatant of the digests had disappeared after 4 hr of fermentation. Fermentability of oat and wheat β-glucan reflected solubility differences, and both sources of β-glucan were completely fermented in 24 hr. Although the overall patterns of fermentation indicated the relative amounts of soluble and insoluble fiber, the anatomical origin of the tissues played a major role, presumably related to the degree of lignification and other association with noncarbohydrate components.