STRUCTURAL CHARACTERISTICS OF STORED BLACK BEANS (PHASEOLUS-VULGARIS L.)

Scanning electron microscopy (SEM) was used to study and compare the s tructural characteristics of black beans after 2 years of storage unde r ambient conditions (AC) and refrigerated hypobaric conditions (RHC). The exterior surface of the seed coats of the black beans were covere d with small flake-like materials randomly clustered together. The hil ar regions of black beans stored under either AC or RHC were similar, and the ''linea lucida'' exhibited well defined double palisade cell l ayers in both bean treatments. Cross sections of the seed coats reveal ed 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 occa sional intercellular spaces between the cell layers. Cotyledon cross s ections of black beans showed that the cotyledon cells of the beans st ored under RHC exhibited many large intercellular spaces characteristi c of normal beans. Conversely, cotyledon cross sections of the beans s tored under AC exhibited cotyledon cells with few small intercellular spaces characteristic of hard-to-cook beans.