Physicochemical changes in dietary fiber of green beans after repeated microwave treatments

The influence of microwave cooking/reheating on dietary fiber in green beans was investigated. The beans were analyzed after blanching and following repeated microwave treatment. Content and composition of dietary fiber as well as molecular weight distribution and viscosity of indigestible water-soluble polysaccharides (WSP) (Mw >1000) were determined. Total fiber content decreased only after the most severe microwave treatment, primarily due to losses of soluble dietary fiber (pectic polymers). Molecular weight and viscosity decreased considerably after the first microwave treatment. Repeated microwave treatments reduced the molecular weight further, but not the viscosity