enhanced solubility of extruded b-glucans may be attributed to the extrusion-induced molecular alterations(Jiang and Vasanthan, 2000).The dietary fiber (IDF, SDF and TDF) contents of the native and extruded barley flours are shown in
Table 3. In general, the contents of SDF and TDF increased upon extrusion cooking of both types of barley flours. The changes in the IDF content were found to be variety-dependent. A minor decrease (compared to native flour) in IDF content of CDC-Candle barley was evident at all extrusion temperatures (Table 3). This suggests that the increase in TDF of CDC-Candle flour,upon extrusion cooking, was primarily due to the increase in SDF. This increase in SDF could be partially due to the transformation of some IDF into SDF during extrusion. In a study involving white and wholemeal
wheat flour, Bjo¨ rck, Nyman, and Asp (1984) have reported a slight increase in TDF with a substantial shift from IDF to SDF in the extruded white wheat flour. In the present study, the % increase in SDF in extrusion-cooked CDC-Candle flour was considerably higher than the decrease observed in IDF (Table 3),suggesting the formation of additional SDF from nondietary fiber components (i.e. starch) of native flour.Theander and Westerlund (1987) reported that highly reactive anhydro-compounds (i.e. 1,6-anhydrosaccharides)were generated during extrusion cooking and these compounds would react with starch or fragmented