Microstructure of Produce Degradation 551
A cross section of the fresh red seedless grape reveals thin epidermal cells, small
exocarp cells with slightly thickened cell walls that look as if they are filled with
pigmented cytoplasm, and large, thin-walled parenchyma cells in the mesocarp
(Figure 18.15a). A damaged grape (Figure 18.15b) looks as if it were pierced by a
foreign object that was then removed. The object damaged the external and internal
tissues and resulted in growth of callus tissue on the surface and in the interior of
the tissue.
Cell walls and cells lost turgor and showed the effects of dehydration (Figure
18.15c). Cell walls in the fresh sample were angular in shape and tightly appressed
(Figure 18.15d). Cell walls in the aged sample were reticulated and intercellular
spaces became more apparent (Figure 18.15e). Cells in the aged sample appeared
to have thickened cell walls or middle lamella, which may have been disintegrating
(Figure 18.15g); this was not apparent in cells in the fresh sample (Figure 18.15f).
FIGURE 18.14Scanning electron micrographs of skin of red seedless grape. (a) Fresh
sample showing smooth surface. (b) Aged sample showing minor dimpling. (c) Aged sample
showing major wrinkling. (d) Aged sample showing major surface wrinkling with embedded
debris. (e) Aged sample; close view of a minor wrinkled area. (f) Aged sample showing
disrupted cuticular wax. Magnification bars: a, c, d, 500 μm; b, f, 100 μm; e, 200 μm.