Chemical and microstructural characterization of easy- and hard-to-cook Jack bean (Canavalia ensiformis (L.) DC.) collections

Differences in the microstructure and the chemical composition of pectic polymers were investigated from three Jack bean collections with different hard-to-cook (HTC) levels, as confirmed by the optimal cooking time analysis. These collections showed different cell and starch granule sizes, where the hardest-to-cook bean (Jombang collection) had the smallest maximum cell perimeter (285 μm), the smallest starch granule perimeter (98 μm), and the highest frequency of small intercellular space indicating more linkage in the middle lamella. No significant difference was observed in the frequency of small intercellular spaces between Malang and Cilacap despite having different optimal cooking times. Jack bean cotyledon cell walls were mainly composed of insoluble polysaccharide rich in arabinose and galactose. The beans contained high covalently bound pectin fractions (NEF) ranging from 78% to 83%. Higher bound phenolics (ferulic acid) were found with the increase in the optimal cooking times of the collections. Overall, the findings suggest the occurrence of cell wall linkage and highlight the importance of ferulic acid pectin crosslink in HTC Jack bean. This study could help develop strategies to reduce cooking time to promote the utilization of Jack bean.