Food Structure


Differences in structure, water uptake and efflux of solubles were found between normal and hard-to-cook beans (Phaseolus vulgaris L.) The staining characteristics of hard beans were different from those of the normal in both non-cooked and cooked tissue, especially in the cell walls. The three zones of the cell wall - the middle lamella, the primary and the secondary walls - were found in both normal and hard-to-cook beans. The primary cell wall of both normal and hard beans was partially degraded upon cooking, as seen by bright fields within the fibrillar pattern. The ultrastructure of the non-cooked secondary cell wall was significantly different between normal beans disintegrated upon cooking, while that of hard beans was retained. Hard beans took up less water during soaking but released more solubles to the medium than normal beans.

It is concluded that the resistance of the middle lamella to solubilization upon cooking prevents cell separation, and this results in the hard texture of the hard-to-cook beans.

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