SOFTENING KINETICS OF COOKED DRY BEANS AT TEMPERATURES BELOW 100C

ABSTRACT New value‐added dry bean products, such as sugar‐coated beans, require a shorter cooking time (15–30 min) and lower temperature (under 100C) than typical canned beans. Michigan bean classes navy, great white northern, small white, small red, dark red kidney, light red kidney, vine cranberry, bush cranberry, pinto and black beans were cooked at constant water temperatures of 90, 95 and 99C for 5–120 min. Isothermal rate constants for texture were estimated at each temperature for each bean class based on a modified first‐order model and an nth‐order model. Heat transfer coefficients were estimated using aluminum beans and lumped capacity analysis. Isothermal parameters (rate constant and activation energy) and a nonisothermal parameter (activation energy) were used to predict texture from dynamic‐temperature experiments. The first‐order model (isothermal) was accurate up to 30 min, but was not appropriate for time greater than 30 min. The nth‐order was considered superior to the modified first‐order model, because only three rather than four parameters needed to be estimated for similar accuracy. The nonisothermal method can save experimental time compared with the isothermal method, because additional experiments at different constant temperatures are unnecessary. A nomograph of equivalent heating time versus constant heating temperature was shown as a useful tool for process design.