Thermal treatment can modify the physicochemical properties of dietary fiber (DF). The study was conducted to evaluate the effect of thermal processing on soluble DF fraction of wheat samples subjected to in vitro gastric and intestinal digestion. Samples were treated by heating in a forced air oven at 150ºC for 5, 10 and 15 minutes, and by exposing to radiations in a microwaves oven for 30, 60 and 90 seconds. The effect of digestive enzymes action on the soluble DF fraction was evidenced by the variation in the dynamic viscosity (DV) of the supernatant collected after gastric and intestinal incubation. Regardless of the heat treatment, DV increased during processing and during digestion. Maximum DV values were observed at 240 minutes of intestinal digestion, after 90 seconds exposure to microwaves.