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Effect of heat processing on immunoreactivity and in vitro digestibility of wheat gluten
B. Mattioni (1), A. de Francisco (1), M. Tilley (2) (1) Universidade Federal de Santa Catarina, , Brazil; (2) USDA-ARS CGAHR, Manhattan, KS, U.S.A..

Approximately 1% of the world population has an autoimmune response to gluten, such as celiac disease, gluten ataxia or dermatitis herpetiformis. Found in wheat, barley, rye and some oat varieties the gluten network is composed of multiple subunits of prolamin and glutelin. Formation of the gluten network is especially important in wheat based products as it confers viscoelasticity and enables dough to be processed into bread. The aim of our study was to investigate the influence of different heat treatments applied to wheat flour on the immunoreactivity and <i>in vitro</i> digestibility of wheat protein. Commercial wheat flour (<i>Triticum aestivium</i>) from Cooperativa AgráriaAgroindustrial, de Guarapuava, Paraná – Brazil, 2012 harvest underwent extrusion, dry heat oven, ultrasound, spray-drying and microwave treatments. After processing, the samples were lyophilized. Protein digestibility and total protein before and after processing was determined on all samples. Immunoreactivity potential to celiac disease was tested by ELISA R5 (Prolamins Kit - TRANSIA® Plate Prolamins - BioControl Systems, USA) and G12 analyses (AgraQuant® Gluten G12 ELISA kit - Romer Labs, USA). A decrease in protein digestibility was observed in samples subjected spray-drying, ultrasound and extrusion (17.8%, 8.6% and 3.0%, respectively). Immunoreactivity using the R5 antibody decreased with spray-drying (47.4%) but increased with other heat processing, especially with extrusion (36.8 %). Using the G12 antibody all samples showed a decrease in immunoreactivity compared to untreated flour, with highest decrease with spray-dry (52.6%). Heat processing leads to unfolding of peptide chains, changes in hydrophobicity and susceptibility to the action of proteolytic enzymes, and could influence immunochemical reactivity.