Role of Cuticles in Produce Quality and Preservation 45
from moisture delivered through the vascular system typically occurs at times when
the transpiration rates are low. The cuticle plays a role in this type of cracking
because its properties affect transpiration rate and provide some mechanical strength
to counter swelling and cracking. The cuticle may play an even greater role in
cracking that results from absorption of moisture directly through the cuticle. In this
case, the cuticle composition and its thickness affect moisture permeation rates.
Also, the mechanical properties of the cuticle (strength and elasticity) determine
how much stress the cuticle can withstand before it tears or cracks. Once the cuticle
cracks, it allows for greater influx of water, resulting in further swelling. Eventually,
deeper cracks form and penetrate the flesh.
Losses due to flesh cracking have been estimated for different kinds of produce
and have considerable economic importance. However, the economic importance of
cuticular cracking has not been estimated and remains difficult to assess because
the cracks are so small. Nevertheless, it is clear that they often precede flesh cracking.
In addition, they may also form by themselves without flesh cracking ever develop-
ing. In such instances, the produce becomes predisposed to pathogen infection and
desiccation. Consequently, produce packinghouses need to be aware of produce that
is susceptible to cuticular cracking. Exposure to water, even for short periods, can
result in some cuticular cracking. The use of water to wash or convey fruit in
packinghouses or to mist fruit on store shelves should be used with caution. In
addition, shipping conditions that favor moisture condensation on the surface of the
produce should also be avoided.
2.9 SUMMARY
The cuticle affects the aesthetic properties of produce and protects produce from
solar radiation and chemical damage that can occur from exposure to agricultural
pesticides and fertilizers. Moreover, it provides some mechanical protection from
bumps, abrasions, and insect damage.
The postharvest life of produce is commonly extended by refrigeration or mod-
ified atmosphere storage, both of which reduce the rate of senescence and maturation
[1]. There is some evidence that the cuticle modifies the internal gas composition
of produce, which, in turn, could influence the rate of respiration and senescence.
Postharvest life of produce is also affected by pathogen infestation. One way the
cuticle extends the postharvest life of produce is by reducing the rate of infection
by microbes [1]. The cuticle plays an important role in providing a physical barrier
to pathogens. Pathogen infestation is much higher in produce with cracks that
penetrate the cuticle, skin, or flesh. The cuticle also affects the events leading to
infection of produce by providing a store of molecules that elicit a pathogen response
and a host defense response during the initial steps of infection.
One of the best ways to extend the life of produce is to minimize water loss [1].
Because one of the primary functions of the cuticle involves controlling moisture
loss, the cuticle plays a critical role in produce quality and preservation. Cracks in
the cuticle layer accelerate desiccation, resulting in the loss of salable weight.
Moisture loss also diminishes the quality of produce due to wilting, shriveling,
softening, flaccidity, limpness, and loss of crispness and juiciness [143]. Moisture