[Analysis of whole gliadin from untreated and heat-treated flour with phase inversion high pressure liquid chromatography]

The gliadins from various wheat flours either untreated or heated (baking, cooking, roller-drying, extrusion-cooking) were extracted with 70% ethanol and analysed by RP-HPLC. When flours are heated below 80 degrees C the chromatograms showed no significant change. At temperatures about 80-90 degrees C a peak appeared in all samples (with the exception of durum wheat) at a retention time of 35 min (peak 35) or, if already present, become more pronounced. A further increase in temperature or treatment time resulted in an increase in this peak whereas the peaks of the more strongly bound gliadins slowly disappeared. In the gliadins of the bread crust the amount of peak 35 decreased again. Similarly, changes were observed in the distribution of the apparent molecular weights of gliadins from heated flours by using gel electrophoresis (SDS-PAGE). At temperatures about 80-90 degrees C the bands between 50-62 kD (under reducing conditions) appeared or become stronger. Their intensity increased with increasing time and treatment temperature whereas the lower molecular weight bands slowly disappeared. Peak 35 may be useful as an indicator of gliadin in heat-treated "gluten-free" foods.