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Effects of extrusion parameters on in vitro starch digestibility and beta glucan solubility of whole grain oats 
S. BRAHMA (1), S. A. Weier (1), D. J. Rose (1). (1) University of Nebraska-Lincoln, Lincoln, NE, U.S.A.

<i>Several studies show that processing conditions affect the water-extractability of beta-glucan in whole grain oats, which may influence the rate at which starch is digested. The purpose of this project was to determine the effects of extrusion parameters on in vitro starch digestibility and beta glucan solubility. Whole grain oat flour was extruded under different barrel temperatures (100oC and 130oC), moisture contents (15%, 18% and 21%), and screw speeds (160 rpm, 300 rpm and 450 rpm). Extrudates were then subjected to in vitro digestion. While barrel temperature did not have a significant effect on starch digestible fractions, screw speed had a significant effect on both slowly digestible starch (SDS) (p=0.03) and rapidly digestible starch (RDS) (p=0.04), and moisture had a significant effect on resistant starch (RS) (p=0.02). Lower moisture (15%) led to higher RS (p=0.01), while moderate screw speed (300 rpm) led to higher SDS (p=0.04) and lower RDS (p=0.03). Moisture also had a significant effect on water-extractable beta-glucan (p=0.05), with the lowest moisture (15%) resulting in higher water-extractable beta glucan. No significant effect was found in the weight average molecular weight of water-extractable beta-glucan in the extrudates, which ranged from 1.15×106 to 1.49×106 g/mol. This study will help us to understand how processing conditions influence the digestion profiles of starch in whole grain oats. The increase in RS and SDS fraction by low moisture and moderate screw speed, respectively, is a good indication for health benefits. The RS fraction, in particular, is of primary interest for increasing beneficial bacteria in our gut. </i>

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