USE OF SPECTROSCOPIC AND FLUORESCENCE TECHNIQUES TO ASSESS HEAT-INDUCED MOLECULAR MODIFICATIONS OF GLUTEN

Fresh gluten isolated from soft wheat flour was heated at varying temp eratures for different times: from 45 degrees C for 1 hr, to 110 degre es C for 18 hr; it was then freeze-dried. The solubility of the untrea ted and heated glutens in different solvents under nonreducing and red ucing conditions was determined, and the extracts were analyzed for pr otein composition by sodium dodecyl sulfate polyacrylamide gel electro phoresis (SDS-PAGE) and acid PAGE. The intrinsic fluorescence, the flu orescence developed on titration with 8-aniline-1-naphthalene sulfonat e (ANS), the UV spectra with second derivatives and solution stability were measured on acetic acid extracts of the glutens. Titration with ANS revealed sites with high and low probe affinity (high and low hydr ophobicity). The results show: 1) a hydrophobic modification at 45 deg rees C, this in no way affected the electrophoretic patterns; 2) moder ate changes at 65 degrees C ascribable to conformational modifications ; 3) heating at 90 degrees C or above strongly affected protein solubi lity in acetic acid and produced disulfide supported aggregates. Confo rmational modifications were also evident. In these changes gliadins, except omega-gliadins, and low molecular weight albumins and globulins were the most involved. 4) Heating at 110 degrees C for 18 hr produce d insolubilization not reversed by dithiothreitol.