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Effect of Processing on Functional Properties of Wheat Gluten Prepared by Cold-Ethanol Displacement of Starch

¹Bioproduct Chemistry and Engineering Research Unit, Western Regional Research Center, Pacific West Area, Agricultural Research Service, USDA, Albany, CA 94710. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ²Corresponding author. Phone: 510-559-5866. Fax: 510-559-5818. E-mail: grobertson@pw.usda.gov.

Functional properties of gluten prepared from wheat flour are altered by separation and drying. Gluten was separated and concentrated by batterlike laboratory methods: development with water, dispersion of the batter with the displacing fluid, and screening to collect the gluten. Two displacing fluids were applied, water or cold ethanol (70% vol or greater, -13°C). Both the water-displaced gluten (W-gluten) and ethanol-displaced- gluten (CE-gluten) were freeze-dried at -20°C as a reference. Samples were dried at temperatures up to 100°C using a laboratory, fluidized-bed drier. Tests of functionality included 1) mixing in a mixograph, 2) mixing in a farinograph, and 3) the baked gluten ball test. Dough-mixing functionality was assessed for Moro flour (9.2% protein) that was fortified up to 16% total protein with dried gluten. In the mixograph, CE-gluten (70°C) produced improved dough performance but W-gluten (70°C) degraded dough performance in proportion to the amount added in fortification. In the microfarinograph, there was a desirable and protein-proportional increase in stability time for CE-gluten (70°C) but no effect on stability for W-gluten (70°C). Baking was evaluated using the baked gluten ball test and the percentage increase in the baked ball volume relative to the unbaked gluten volume (PIBV). PIBV values were as high as 1,310% for freeze-dried CE-gluten and as low as 620% for W-gluten dried at 70°C. PIBV for CE-gluten was reduced to 77% of the freeze-dried control by fluid-bed drying at 70°C. Exposure of CE-gluten to 100°C air gave a PIBV that was 59% of the reference, but this expansion was still greater than that of W-gluten dried at 70°C. The highest values of PIBV occurred at the same mixing times as the peak mixograph resistance.