MODELING OF BEAN HARDENING KINETICS DURING STORAGE

Two kinetic models ('empirical' and 'logistic') were adapted to predict storage-induced hardening of black and white beans, A database consisting of 451 observations gathered using black bean samples at 38 different storage conditions and 155 experimental data points corresponding to white beans stored at 12 different conditions was utilized to validate the proposed equations. Compared to other published models, the ones developed in this study were not limited to mild storage conditions or short storage times. Hardening showed an initial lag period, followed by a period of fast hardening, and ending in a period of declining hardening rate as hardness plateaued to equilibrium values at adverse storage conditions. Hardening rates increased with either the water activity of beans or storage temperature, whereas equilibrium values were only determined by sample water activity, for black beans, or temperature, for white beans. Both models used the activation energy and equilibrium constant of the hardening reaction as parameters, which could be assumed to be independent of the sample storage conditions and still allow an adequate fit between experimental and predicted values.