Soaking kinetics of quinoa seed (Chenopodium quinoa Willd). Mathematical modeling: Applying analytical and empirical models

Abstract

Quinoa is a nutritionally valuable pseudocereal due to the favorable amino acid profile of its proteins compared to other seeds and grains. The goal of this study was to investigate the soaking kinetics of quinoa seeds. Experimental curves of moisture content versus time were obtained for a water temperature range of 20 ℃ to 70 ℃. Regarding the soaking process empirical equations such as Peleg, Weibull, and Exponential and an unsteady state diffusional model with a strict internal control of the mass transfer rate. Calculations by empirical models were markedly accurate for water uptake with r2 higher than 0.95 and RMSE values lower than 0.09. On the other hand, the complete analytical solution, which involves an infinite convergent series for constant diffusivity (Deff) and constant radius (R0), provided a reliable prediction of soaking kinetics. Values of the diffusion coefficient (around 10−11 m2/s) are within the ranges expected for food rehydration at similar temperatures. The activation energy and pre-exponential factor were calculated by an Arrhenius type-equation. The values determined were Ea = 9.1 kJ mol−1 K−1 and, D0 = 3.861 × 10−10 m2 s−1, respectively with an r2 value lower than 0.8.