Structural changes during the retrogradation of legume starches modify the in vitro fermentation
1993
Abia, R. | Buchanan, C.J. | Saura-Calixto, F. | Eastwood, M.A.
The fermentation of native and retrograded starches from white beans (Phaseolus vulgaris), lentils (Lens culinaris medicus), chickpeas (Cicer arietinum L.) amylose, and native amylopectin has been studied. Starches were extracted from legumes, and a portion was made resistant to amylolysis (retrograded starch) by repeated autoclaving and cool% cycles. The retrograded fraction was isolated by treatment with heat-stable alpha-amylase, protease, and amyloglucosidase. Samples were fermented using an in vitro batch-culture technique under anaerobic conditions with rat cecal contents as inoculum. Short-chain fatty acids, lactic acid, cell growth, and starch-degrading enzymes were analyzed after 3, 6, 18, 24, and 48 h of fermentation. The rate of production of total acids (acetic, propionic, butyric, and lactic acids) was different between each of the retrograded starches at all times studied. Retrograded amylose and bean starch were fermented at a slower rate than retrograded lentil and chickpea starches. Significant differences were observed after 18 and 24 h of fermentation of native starches. Scanning-electron micrographs of the resistant starches after the autoclaving-cooling treatment and the in vitro enzymatic digestion showed changes in the physical appearance between starches. Such physical changes could have affected the accessibility to bacterial enzymes and therefore the fermentability of the starches.
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