Cereal Chem 61:174 - 179.  |  VIEW ARTICLE
Extrusion Cooking and Dietary Fiber: Effects on Dietary Fiber Content and on Degradation in the Rat Intestinal Tract.

I. Bjorck, M. Nyman, and N.-G. Asp. Copyright 1984 by the American Association of Cereal Chemists, Inc. 

Dietary fiber content in raw and in extruded wheat products was measured gravimetrically after enzymatic solubilization of protein and starch. Dietary fiber content of whole grain wheat increased slightly after extrusion cooking, whereas the fiber content in wheat flour only increased after processing under extreme conditions. When the heat-stable alpha-amylase Termamyl, used in the dietary fiber assay, was excluded, the increase in dietary fiber was more pronounced. A redistribution of insoluble to soluble dietary fiber was observed in all extruded wheat flour samples. In raw wheat flour, 40% was soluble, whereas in extruded wheat flour, 50-75% was soluble. The redistribution in whole grain flour was less pronounced. The degradation of dietary fiber monomers in the rat intestine was very similar with raw and extruded whole grain wheat flour. However, the dietary fiber in extruded wheat flour was more extensively degraded than in the corresponding raw material. Fecal glucan excretion did not increase when extruded materials were fed, which indicated that altered starch was completely absorbed or fermented. Rats fed wheat flour extruded under severe conditions developed diarrhea.