Mechanical and Temperature Effects on Shelf Life Stability of Fruits and Vegetables - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 40

In developed countries, harvesting of selected vegetable and fruit crops has been
mechanized. Losses due to mechanical damage can be high and these have been
associated with poorly designed equipment. Harvesting of potatoes is mostly done
by mechanical harvesters. Increasing mechanization for transport, grading, and mar-
keting had been practiced in recent years. There have been reports of damage to
tubers due to the design of potato harvesters or improper operation. Horvath 4
observed that the size and temperature of the tubers are two important contributory
factors causing damage of potatoes during harvest. Impact injury may be inflicted
on mechanically harvested fruits when they are dislodged from the tree. 5
F IELD P ACKAGING AND T RANSPORT TO THE P ACKINGHOUSE
The harvested crops are placed in a variety of containers such as baskets, sacks,
wooden boxes, and plastic crates for transport to the packinghouse. Some containers
are either too flexible or their inside surfaces are too rough, that they often do more
harm rather than protect the commodity from handling damage. In some instances,
the products may be packed too tightly or too loosely causing compression damage
and bruising. Also, the filled container may be subjected to rough handling. When
transport to the packinghouse is not immediately available, produce-filled containers
often wait under the sun.
P RODUCE P REPARATION FOR P ACKAGING
Inside the packinghouse the produce is initially sorted, cleaned, graded, subjected
to quarantine treatments, and, in some cases, waxed before packaging. Mechanical
injury is the main cause of quality loss in packinghouses. Quarantine treatments
should be properly tested and approved before their application in the packinghouse.
These may involve the application of heat, chemicals, or a combination of both.
Temperature stress or heat damage may also occur, when the commodities are exposed
to heat treatment. Each time a product item comes in contact with another item or
with the equipment in the packinghouse, damage may be inflicted. As an example,
the following sequence of events has been identified to cause cumulative damage
or bruising on apples as they go through transport from storage to packinghouse:
flotation out of the storage bin; accumulation of water at the line input; elimination
of trash and undersized fruit; manual grading; washing in brushes; dewatering on
sponge rolls; waxing; drying on a roller conveyor; manual inspection; singulation;
sizing; accumulation; packing or bagging; and stacking on a shipping pallet. 6
P RECOOLING
Precooling is the immediate removal of field heat from the commodity. High ambient
temperatures are favorable for the deterioration of the produce since respiration and
transpiration rates are high. Heat is removed from the commodity as a preparatory
step in the refrigerated storage and transport of the product. The shelf life of the
produce is considerably shortened if it is not promptly cooled because respiration
and transpiration continue after harvest.