Mechanical and Temperature Effects on Shelf Life Stability of Fruits and Vegetables - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 39

of the skin, and presence of protrusions on the skin surface. Texture of the produce
is adversely affected by excessive water loss, rendering the product unmarketable.
R IPENING
This is a natural development process that mature fruits undergo, giving them
desirable texture, taste, and flavor. However, it is followed by senescence and break-
down of the fruit. Ripening of fruits often leads to increased susceptibility to
mechanical injury and attack of pests and diseases.
P OSTHARVEST D AMAGE
This consists of any loss in quantity or quality of the produce after harvest that may
be caused by mechanical injury or injury from temperature effects. Losses by
mechanical injury begin from the time of harvest until the produce reaches the
consumers' table. Bruises, cuts, splits, and cracks are some of the manifestations of
mechanical injury. These trigger an increase of physiological processes, which can
be disastrous to the produce. Injury from temperature effects is caused by exposing
the produce to extremes of temperature during postharvest handling. Heat, freezing,
and chilling injury can be prevented if appropriate environments are provided during
handling. These injuries cause a reduced shelf life of crops, especially fruits and
vegetables. Insects usually infest the crop while in the field, depositing their larva
or egg on the produce, while fungi and bacteria infect the produce causing diseases.
Pests and diseases can be controlled by quarantine treatments employing physical
and chemical methods or a combination of the two.
POSTHARVEST HANDLING
Handling operations vary according to the produce. Some fruits, such as citrus, are
waxed to improve their appearance and prolong storage life by serving as a fungicide
carrier. Ethylene may also be applied to fruits to induce ripening among climacteric
fruits such as bananas, and enhance uniform color and improve marketability among
fruits. The following operations can subject agricultural products to mechanical and
temperature stresses.
H ARVESTING
Harvesting is the collection of the produce that may involve picking, cutting, digging,
or shaking, and presents an opportunity for the crop to be mechanically damaged.
After harvesting, the produce may be thrown or dumped in the container and may
come in contact with the hard surface and sharp edges of the container or collide
with other products. Some trimming and sorting are done on the produce during
harvest. Injury may result when under-trimmed products collide with each other and
excessive water loss may occur if products are over-trimmed. Tomatoes are sorted
according to color or presence of defects, while cabbages, carrots, radishes, and
some leafy vegetables are trimmed or topped in the field.