Structural characteristics of stored black beans (Phaseolus vulgaris L.)

Scanning electron microscopy (SEM) was used to study and compare the structural characteristics of black beans after 2 years of storage under ambient conditions (AC) and refrigerated hypobaric conditions (RHC). The exterior surface of the seed coats of the black beans were covered with small flake‐like materials randomly clustered together. The hilar regions of black beans stored under either AC or RHC were similar, and the “linea lucida” exhibited well defined double palisade cell layers in both bean treatments. Cross sections of the seed coats revealed that the parenchymal cell layers of the beans stored under AC were disrupted and frequently exhibited large intercellular spaces between the cell layers. The parenchymal cell layers of the beans stored under RHC demonstrated little disruption of the cell layers, with only occasional intercellular spaces between the cell layers. Cotyledon cross sections of blackbeans showed that the cotyledon cells of the beans stored under RHC exhibited many large intercellular spaces characteristic of normal beans. Conversely, cotyledon cross sections of the beans stored under AC exhibited cotyledon cells with few small intercellular spaces characteristic of hard‐to‐cook beans.