128: Pasting Properties, Drying Kinetics, and Modeling of Raw, Cooked, and Precooked Flour From Wild Yam (Dioscorea Remotiflora)

Introduction

The consumption of yam plays a significant role in the diet of the population of low-income countries, because of its high carbohydrate content. The most common preparation method is boiling; however, converting yam into flour extends tubers' shelf life and diversifies its uses in baking, pasta production, or as a substitute for other flours. Currently, there are limited proposals for the industrialization of yam (Dioscorea remotiflora) native to Jalisco Mexico, and its potential for producing high-value food products. Therefore, this study aimed to produce flour and evaluate the effects of precooking and cooking on their pasting properties and drying kinetics.

Methods

Tubers were washed, peeled, and cut for partial and complete cooking to obtain precooked and cooked flour, respectively. The raw material was sliced to produce raw flour. Both raw and thermally treated materials were dried at 65°C in a convection oven, milled and sieved to obtain flour. Pasting properties were determined using a rapid viscosity analyzer (RVA 4500, Perten instrument). Drying curves were constructed from 3-5 mm slices of dehydrated yam in a convective dryer at 65°C and air flow of 0.1 m/s. Weight loss was recorded at different times until constant weight. Drying behavior modeling was performed using the MatLab software.

Results

Significant differences (p < 0.05) in peak viscosity were observed for raw (482.25 RVU), precooked (184.08 RVU), and cooked (21.46 RVU) flours. The drying times were 405, 330, and 345 min, for precooked, cooked, and raw flours. Particularly for precooking, starch forms a film that limits water transfer from the product to the exterior, extending drying. With modeling, higher R2 values were observed for the Page (0.9939-0.9986) and the Logarithmic (0.9836-0.9920) equations, while the other models showed lower R2 (0.9691-0.9836). Thus, the Page and Logarithmic models provided a better fit, with lower statistical error (RMSE), describing the drying process more accurately.

Significance

Flours are a stable form of preserving cereal grains and tubers like wild yam. The processing method affects flour's properties and potential applications. Thus, cooking parameters and starch retrogradation are crucial factors. Meanwhile, the drying behavior and mathematical models help predict drying times for optimal process conditions.

Authors: Y. Estrada-Girón, E. Villareal-Flores, V.V.A. Fernández-Escamilla and M.I.D. Romero-Pérez