Objective methods to evaluate rheological properties of wheat flour tortilla dough

Abstract

Characteristics of wheat flour tortilla dough were measured on a texture analyzer using texture profile analysis (TPA), stress relaxation, extensibility and adhesiveness tests. Doughs were optimally mixed, rested, divided, rounded and sampled during resting. Concentrations of water, fat, reducing agent and acidulants were varied to prepare a viscoelastic solid, viscoelastic liquid, and control doughs for subjective and objective evaluations of dough properties. TPA hardness and resilience exhibited low variability (CV= 1-9%) and correlated significantly with subjective dough properties (smoothness, r--0.88; softness, r--0.90; toughness, r--0.91). TPA adhesiveness and springiness were not sensitive to differences in doughs during resting or by dough formulations and among doughs.Resistance to extension and dough extensibility showed low variability (CV= 3-12%). Dough extensibility method was sensitive enough to indicate significant differences during resting and among doughs. Both parameters gave significant correlations with subjective dough evaluations (resistance to extension, softness, r-0.95; toughness, r--0.95; extensibility, softness, r---0.85; toughness, r---0.86). Adhesive force measured by Chen-Hoseney dough stickiness method showed moderate variability (CV= 5-17%), but failed to differentiate the doughs. This method was insensitive to changes during resting since a freshly mixed dough surface was created for testing. Adhesive force correlated significantly with subjective dough properties (smoothness, r = 0.89; softness, r--0.89; toughness, r = 0.89). Equilibrium modulus (stress relaxation) showed low variability (CV= 7-10%) and correlated significantly with subjective dough evaluations (softness, r--0.95; toughness, r--0.96). TPA and dough extensibility, were utilized to evaluate doughs made from different formulations and processing conditions. Tortillas were made to determine the relationships between objective dough evaluations and tortilla characteristics. Hardness, resilience, and resistance to extension increased and extensibility decreased for doughs containing less fat, less cysteine, and/or more gluten. Dough extensibility parameters correlated significantly with subjective dough evaluations (softness, r-0.60; toughness, r--0.61). TPA hardness and resilience correlated significantly with tortilla characteristics (diameter, r=-0.58; height, r--0.65; weight, r--0.66). TPA (hardness and resilience) and dough extensibility methods were effective in characterizing dough properties. However, practical application of these objective Theological methods must be confirmed in commercial tortilla plants.