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Role of Gluten in Flour Tortilla Staling

¹Cereal Quality Lab, Dept. of Soil & Crop Sciences, Texas A&M University, College Station, TX 77843-2474. ²Corresponding author. Phone: 979-845-2925. Fax: 979-845-0456. E-mail address: jnalviola@neo.tamu.edu

Effects of protease and transglutaminase (TG) on dough and tortilla microstructures, shelf-stability, and protein profile were determined to infer the role of gluten in tortilla staling. Control and enzyme-treated tortillas were prepared using a standard bake test procedure and evaluated for three weeks. Confocal micrographs of control dough showed thin protein strands forming a continuous web-like matrix. Protease-treated dough had pieces of proteins in place of the continuous matrix, while TG-treated dough had thicker protein strands that were heterogeneously distributed. Control tortillas had a well-distributed continuous protein structure. Protease-treated tortilla had a continuous structure despite being composed of hydrolyzed proteins in the dough, while the TG-treated tortilla retained clumps of proteins. Both treatments resulted in shorter shelf-stability of tortillas. An evenly distributed and moderately stronger gluten network is necessary for longer retention of tortilla flexibility. Solubility of protein fractions differed among treatments, but molecular weight distribution did not differentiate control and treated dough or tortillas. The proportion of each protein fraction appears to affect staling.