Mathematical Modeling and Analysis of the Amaranth Drying Curve: Evaluation of Functional Properties

Introduction: The use of mathematical models to understand the dehydration of amaranth improves the efficiency and quality of drying, benefiting costs, sustainability, and product innovation. Objectives: The main objective was to validate different mathematical models that accurately describe the drying process, allowing the determination of the kinetic and thermodynamic parameters that govern it, as well as the physicochemical and functional characteristics of the resulting amaranth flour. Methods: Amaranthus dubius seeds were cleaned, disinfected, cooked at 70°C for 30 minutes, and then dried at 60, 70, and 80°C in a tray dryer with controlled airflow. Dried samples were ground and sieved. Moisture content during drying was modeled using five mathematical models, Page, Midilli, Lewis, Logarithmic and the de Henderson y Pabis. The effective moisture diffusion coefficient and activation energy were determined using Fick's second law and the Arrhenius model. Functional properties such as water retention capacity, oil absorption capacity, and gelation capacity were evaluated using standard methods. Statistical analysis included ANOVA and Tukey’s test with a significance level of p < 0.05. Results: the Midilli model being the one that best adapted to the experimental curves, demonstrating precision in representing the drying curve of amaranth flour. On the other hand, lower moisture percentages (9.09 ± 0.15%) and water activity (0.45 ± 0.00) were found when the drying temperature was 80 °C, and the obtained flour showed a remarkable water retention capacity, while the emulsifying capacity showed its highest value in the flours obtained at 70 and 80°C. These findings underscore the importance of selecting the drying temperature properly in the production process of amaranth flour, as it can significantly influence its physical and functional properties, which in turn impacts its suitability as a functional ingredient for formulating various types of foods. Conclusions: the results obtained in this study allowed us to conclude that the Midilli model was the one that best adapted to the experimental curves, demonstrating its precision in representing the drying behavior of amaranth flour. Furthermore, it was found that a drying temperature of 80 °C resulted in the lowest moisture content and water activity, which translates into greater product stability. The flour obtained at this temperature exhibited a remarkable water retention capacity, while the emulsifying capacity reached its highest values in the flours dried at 70 and 80 °C. These findings highlight the importance of selecting an appropriate drying temperature during the production process, as it can significantly influence the physical and functional properties of amaranth flour, directly impacting its suitability as a functional ingredient in the formulation of various foods.