Repeated cooking and freezing of whole wheat flour modifies in vitro starch digestion and fecal fermentation
J. A. ARCILA-CASTILLO (1), D. J. Rose (1)
(1) University of Nebraska Lincoln, Lincoln, NE, U.S.A.
Resistant starch (RS) is a fermentable dietary fiber that has shown tremendous benefits on gut health, but it is present in only small amounts in most grain-based foods, including those made with whole grain. The purpose of this study was to increase RS in whole wheat flour in order to improve its potential health benefits. In this study, a sequence from 0 to 7 cycles of cooking (20 min, boiling water) and freezing (-18 oC, 23 h) of whole wheat flour in water (1:15 w/v) were performed in order to drive retrogradation of the starch. During in vitro digestion, increasing the number of cooking-freezing cycles from 0 (control) to 7 progressively increased RS from 1.03% to 8.07% of the total starch. Digested flours were then subjected to in vitro fecal fermentation. Increasing cooking-freezing cycles resulted in an increase in total short chain fatty acids (SCFA), mainly propionate. Increases in butyrate were also noted, but only during the first 8 h of fermentation. All flours including the control resulted in significant increases in Bifidobacterium of >0.5 log during fermentation compared to baseline. Increased cooking-freezing cycles showed a trend toward higher Bifidobacterium at the end of fermentation (p=0.08). Our results demonstrate that it is possible to manipulate the native starch fractions in whole wheat flour to produce changes that are consistent with improved gut health. In the present study, even modest increases in the RS content of whole wheat flour modulated the metabolic activity of gut microbiota to increase production of beneficial metabolites such as SCFA.
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