Microstructure of Produce Degradation 541
determined mainly by the state of the middle lamella. Fruits and vegetables are
dynamic, living systems; thus, structural and textural changes occur continuously.
Textural diversity at the cellular level has been studied in various tissues using tensile
strength measurements and correlating the measurements with observation by
microscopy. Examination of the fracture surfaces allowed the detection of differences
in tissue strength and juiciness and provided insight into the cellular basis of plant
texture. It also helped to identify specific cell characteristics that influence the
sensory texture attributes of “hardness” and “juiciness” [19].^
Soft texture is a desirable characteristic in kiwifruit. In contrast to cells of apple
fruit, kiwifruit cells remain in close apposition, whereas apple cells have more
intercellular spaces and have very little cell-to-cell contact. The intercellular spaces
account for part of the reason the two fruits have such differing textures [20].
FIGURE 18.8Cucumber. Scanning electron micrographs exhibiting cross-sectional views of
the aged fruit. (a) Outermost edge shows the epidermis, exocarp, and mesocarp; the fruit has
huge gaps in the mesocarp adjacent to the junction of the exocarp. (b) Close views of the
degenerated area from a. (c, d) Close views of the degenerated area from a. showing the
growth of fungal hyphae (arrows). (e) Exocarp showing thick-walled cells that have no change
from fresh material. (f) Inner mesocarp tissue showing little or no change from fresh material.
Magnification bars: a, 1 mm; b–f, 200 μm.