Produce Degradation Pathways and Prevention

68 Produce Degradation: Reaction Pathways and their Prevention

most affected by the growth of the cells in the tissues, as illustrated in Figure 3.4.
Immature fruits and vegetables are most often harvested at a point in time between
meristematic growth and the end of vacuolated growth. As vacuolated growth pro-
ceeds, cell walls become thicker and more rigid (Cosgrove, 2000), and hence the
tissue becomes tougher. By the time cessation of growth has been reached, the tissue
is definitely fibrous and tough. Another feature of nonclimacteric fruits and vegeta-
bles is that it is more difficult to develop maturity indices for optimal harvest since
they are harvested during time of growth and not after growth has ceased. Most
often, size or morphology of the nonclimacteric fruit or vegetable organ is the main
criterion used for determination of harvest date (Salunkhe and Desai, 1984; Gross
et al., 2002). However, experience with such products has produced practical criteria
for optimal harvest, but challenges still exist.
Optimal harvest of sweet corn is determined by examining two maturity char-
acteristics. The first is ensuring that all of the kernels on the cob are fully sized. The
second is that the kernels must be succulent as measured by the amount of juice
that can be squeezed out of individual kernels (Weichmann, 1987). Overly mature
kernels are very firm and starchy. These kernels lack succulence and are tough, and
this sweet corn is not acceptable to the consumer.
Another challenge is selection of optimal harvest for winter cabbage. There have
been some reports indicating that maturity that optimizes storage potential is related
to the amount of nutrient reserves in the stem (core) tissue (Weichmann, 1987).
However, inconsistencies between years and cultivars have rendered this approach
to maturity estimation unuseful.

FIGURE 3.4Time scale by which plant cell wall growth can be analyzed. Cells graduate
from meristematic growth to rapid expansion accompanied by vacuolation, followed by cessation
of growth. (From Cosgrove, Plant Physiol. Biochem., 38, 109, 2000. With permission.)

Enlargement rate

Meristematic

growth

Time (days)

Vacuolated

growth

Growth

cessation