Study on water absorption kinetics of black beans during soaking

Soaking can affect the final quality of black bean products. The Peleg equation and low field nuclear magnetic resonance (LF-NMR) were used to study the water absorption kinetics of black beans during soaking. From the results, the changing of the water content in black beans during soaking at 30–70 °C can be simulated by the Peleg equation. The rate constant K1 and the capacity constant K2 decreased with an increase of temperature, the relationship between temperature and its corresponding rate constant K1 were fitted to the Arrhenius equation, and the activation energy of the soaking process was 32.09kJmol−1, indicating that the seed hydration rate was more sensitive to temperature. Three proton fractions with different mobility were observed in black beans during soaking, reflecting macromolecule, oil, and water in different microenvironments; the soaking process significantly changed the distribution of proton fractions in black beans. Magnetic resonance imaging (MRI) showed that the water first passes through the uneven wall and then enters the inner region of the black beans along the different channels during the soaking process, leading to significant changes in the texture of black beans.