Thermal and pulsed electric field (PEF) assisted hydration of common beans

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Hydration, a crucial preliminary stage of dried bean processing is mostly performed as a slow, batch-wise process. Here we investigated the effect of thermal and pulsed electric field (PEF)-assisted hydration of two common beans (Phaseolus vulgaris) on hydration behaviour, mass loss and leaching of bioactive components. Beans were hydrated in media either using a thermal process (30–80 °C, 10 °C intervals) until equilibrium moisture content (EMC) was reached or were hydrated to 40 g/100 g dry basis moisture at 45 °C, then PEF-treated at an electric field intensity of 4 kV/cm, f = 2 Hz, pulse width 15 μs, pulse numbers from 200 to 1000 (specific energy from 91 kJ/kg to 455 kJ/kg) and further hydrated until EMC. PEF-assisted hydration reached higher equilibrium moisture values and reduced the hydration time by 3-fold for small red beans (1000 pulses, 455 kJ/kg specific energy) compared to 45 °C soak, however, it also leached higher amounts of bioactive polyphenols into the media. Comparable losses of prebiotic oligosaccharides from beans into the media were found in the two hydration approaches. PEF-assisted hydration is a promising alternative to soaking to reduce process time for slow hydrating beans and leaching of bioactive components could be minimised through process optimization.