Food Structure


Scanning electron microscopy (SEM) was used to study and compare the mic rostructure of adzuki, black and Mexican red bean seeds. The two cotyledons of the beans were separated by a deep fissure. A view of seed coat surface of adzuki beans revealed a characteristic pattern of convolutions and cracks, not observed on the seed coat surfaces of black or red beans. The cro sssection of seed coat of adzuki beans exhibited a thick layer of palisade cells in the epidermal layer followed by underlaid multiple layers of tightly packed parenchyma cells. A sub-epidermal layer comprised of a single layer of hour-glass cells was observed in the black and red bean seed coats but not in adzuki beans. A cross-section of the hilum region of adzuki beans and Mexican red beans exhibited a double palisade layer , a phenomenon not observed in the black beans. The cross-section of the sub-hilar region of the adzuki and Mexican red beans revealed a sub-hilar plug , not observed in the black bean sub-hilar region . The micrographs of adzuki bean cotyledons showed spherical starch granules with an apparent pitted surface and were loosely embedded in a protein matrix . The starch granules of black and Mexican red beans were more oval in shape, with a smoother surface, more compactly packed and embedded in a protein matrix . The microstructural differences of the adzuki bean from the other common food legumes like black beans and Mexican red beans, may be useful to study the relationship between textural and fun ctional properties of these beans.

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