33A-12 |
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G. CEDILLO, A. C. Gutierrez de Velasco, R. D. Waniska, and L. W. Rooney. Dept. of Soil & Crop Sciences, Texas A&M Univ., 429 Heep Ctr., 2474 TAMU, College Station, TX 77843-2474 Fresh tortillas are soft and flexible, but undergo staling soon after baking. Understanding the mechanism of staling would help to maintain the fresh characteristics for a longer time. The objective was to monitor the effect of additives and storage temperatures on texture and starch granule properties of corn tortillas during storage. Tortillas were prepared from nixtamalized corn flour (NCF) with different levels of maltogenic a-amylase, carboxy-methyl-cellulose and guar gum, optimized by response surface methodology. Tortillas were stored four days at refrigeration (4oC) and ambient (25oC) temperatures and subjected to analysis. Tortilla texture was measured by objective (extensibility) and subjective (rollability and pliability) tests. Tortilla samples were dehydrated under vacuum with methanol to stabilize the starch. Solid losses during starch stabilization were recorded. Changes in starch granule properties were monitored in stabilized-starch tortilla residues with Rapid Visco Analyzer (RVA). Subjective texture measurements reflect significant differences (p<0.05) between samples stored at ambient and refrigeration temperatures for most treatments; tortillas stored at ambient temperature had better texture. Within treatments, stabilized-starch residues from tortillas stored at refrigeration gave higher peak and final viscosities than the ones from tortillas stored at ambient temperature. For both storage temperatures young’s modulus was significantly reduced (p<0.05) by addition of maltogenic a-amylase. Lower peak and final viscosities were observed for the stabilized-starch residue from enzyme-treated tortillas than for tortillas without enzyme. Guar gum had a positive effect on tortilla texture. Enzyme-treated tortillas gave significant (p<0.05) higher solid losses during starch stabilization than tortillas without enzyme. Since the RVA measurements and solid losses in starch stabilization reflect modifications induced by enzyme treatment, they could be used to assess the functionality of enzymes that induce modifications of starch. Either RVA or subjective texture tests could be used to monitor the effect of storage temperature on tortilla properties.
Session 33A, Carbohydrate: General
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