Wheat gluten swelling and partial solubility with potential impact on starch-from-gluten separation by ethanol washing

Swelling of wheat gluten may be a contributing factor in washing or displac ement separation of gluten and starch using cold ethanol. To test this hypo thesis, dissolution and swelling (settled volume or mass absorption) of a c ommercial gluten are reported here for the first time as a function of both temperature and ethanol solution concentration. In this test system, insta nt and substantial volumetric swelling was observed over most of the range of ethanol concentrations but not at 100%, v/v, ethanol. Settled volume rea ched a maximum of 50-70%, v/v, ethanol, and this was up to 3.5x the volume in absolute ethanol at 22 degrees C and 2x the volume at -15 degrees C. Thi s maximum closely corresponds to the maximum dissolution of whole gluten an d prior literature reports of full dissolution of gliadin. The reduction of settled volume at low temperature reflects the possible role of undissolve d, gliadin-class proteins in reinforcing the gluten structure and limiting the ultimate swelling. The data suggest gluten-swelling properties as a con tributing factor to the success of the cold ethanol, gluten-from-starch sep aration process.