Precooking and rehydration strategies of common bean seeds (Phaseolus vulgaris L.) determine their regeneration properties

Abstract

Precooking beans prior to drying enables the production of shelf-stable products, prevents the hard-to-cook defect associated with storage of raw beans, and enhances consumer convenience through reduced preparation time. This study aimed at mechanistic insights into how precooking and rehydration strategies influence the regeneration behavior of precooked dehydrated beans. Beans were precooked under different conditions: conventional cooking (30, 45, and 120 min), and limited-water cooking (120 min), to generate varying (micro)structures. Bean microstructure and hardness after each processing step were evaluated and linked to rehydration performance under direct (23 °C, 90 °C) and two-step (23 °C followed by 90 °C) approaches. Extensively precooked beans showed lower hardness, pronounced cell separation, and cell wall thinning. After dehydration (40 °C), these structural changes resulted in a more porous structure with weakened cell wall integrity, which significantly enhanced rehydration capacity and rates ($D_{\mathrm{eff}}$ 2–6 times higher at 90 °C). Two-step rehydration (23 °C/7 h, then 90 °C/10 min) was recommended to avoid grainy texture and white cores, indicative of insufficient hydration. Modeling of rehydration kinetics indicated that at 23 °C, both surface-controlled mass transfer and diffusion governed water uptake, while at 90 °C, diffusion (without surface resistance) was the dominant mechanism. Bean texture after rehydration did not change/soften beyond that established during precooking, despite greater pectin solubilization (an increase in hot-water-extractable pectin), suggesting that pectin solubilization may not contribute to the softening of precooked dehydrated beans. Therefore, beans must be precooked to a palatable level for consumption before dehydration, suggesting a processing criterion to attain desirable texture after rehydration.