Prediction of corn tortilla textural quality using stress relaxation methods

Abstract

Feasibility of the stress relaxation technique which has a strong potential for texture characterization of dough and food products, was evaluated with both corn masa and corn tortillas (These are "low-moisture tortillas" which are ready to be fried). The effects of moisture content and resting time on corn masa textural property were investigated. Texture of properties of corn tortilla (fresh up to stale) was evaluated using the stress relaxation technique in two different modes, pure tension and bending-tension. Experimental data were fitted to the 7-element Maxwell model as well as the Peleg and Normand's model. Biomechanical parameters (stiffness and total energy dissipated) were calculated and used to interpret the changes on textural properties of both corn masa and corn tortilla. The results for tortilla were compared with the subjective rollability score. Stress relaxation technique successfully detected: (1) the textural differences between masa samples with different initial moisture content, and (2) changes in texture of masa as a function of resting conditions and time. Mathematical models were developed to predict the changes. Stress relaxation under pure tension mode showed good correlation with the subjective rollability scores. Stiffness and energy dissipated for tortilla were chosen as best texture property predictors. Stress relaxation under bending-tension mode also exhibited high correlation with the subjective rollability scores for tortillas. Peleg and Normand's model was used to fit the experimental data. k, (an indicator of the rate of stress decay) was selected as the best predictor for corn tortilla. High correlation was observed between the total energy dissipated for fresh corn masa and the value of stiffhess of fresh corn tortilla tested under tension mode. A mathematical model was built to predict the stiffness of fresh corn tortilla from fresh masa characteristics.