Mechanical Injury of Fresh Produce 101
A primary consequence of mechanical damage is increased loss of water and
water-soluble nutrients. This results in shriveling of produce and increased suscep-
tibility to decay-causing pathogens. The use of different precooling methods, such
as hydrocooling and vacuum cooling in broccoli,219, 220 showed beneficial effects in
terms of increased firmness and reduced weight loss. Weight loss has also been
studied in several fruits, such as lemons,^84 oranges,^221 and blueberries.^217 Weight loss
in mechanically damaged fruit is a consequence of modification of tissue perme-
ability and the occurrence of small cracks connecting internal and external atmo-
spheres, allowing the interchange of atmospheric gases, particularly water vapor.^222
Delaying the start of precooling also resulted in greater weight loss and lower tissue
firmness in strawberry fruit.^223 Forced-air cooling led to a reduction in the respiration
rate of mechanically damaged plums. Damaged fruit before precooling showed a
respiration rate double that of damaged fruit after precooling during storage. Dam-
aged plums before precooling showed higher weight losses and lower firmness than
damaged fruit after precooling. Precooling Santa Rosa plums after harvesting and
before manipulation (transportation to the packing house, handling in the packing-
house and during storage or transportation) can help to maintain fruit quality and
prolong shelf life.^83 With respect to color, mechanical damage before precooling
significantly reduced chroma values; plums were darker and less bright than those
damaged after precooling. These color changes resulted in less attractive fruit.
Polyphenol leakage and tissue browning usually accompany mechanical damage.^83
In kiwifruit,^118 reducing the temperature soon after impact decreased ethylene pro-
duction and the appearance of injury symptoms.
Temperatures of 15 to 25°C affected development of pink rot caused by Phy-
tophthora erythroseptica in wounded potatoes. Infections in unwounded tubers
started at 15°C, whereas in wounded tubers infection started at 10°C. Incidence of
pink rot was high at high temperature and high inoculum levels.^224 The susceptibility
of potato tubers to bruising is also greatest when they are harvested at a low
temperature. Tubers harvested at a low temperatures also display a greater severity
of bruising after impact. This detrimental effect of low harvest temperature appears
to be unrelated to polyphenol oxidase activity, catalase activity, or the content of
ascorbic acid but seems to occur through an effect on the permeability of cell
membranes.^225 Prestorage at low temperatures also reduces storage losses in mechan-
ically damaged potatoes. Weight loss was the major component of total loss.^226
Prestorage tended to increase tuber firmness and reduced the incidence of blue spots.
Total loss, weight loss, and dry rot increased with increasing severity of wounding;
total losses were lower in fruit stored at 5°C than in fruit stored at 7°C.
Heating dropped papaya fruit at 48°C for approximately 6 hours or until the
fruit core temperature (FCT) reached 47.5°C aggravated the severity of mechanical
skin injury. Delays in the application of heat treatment from dropping did not reduce
the severity of skin injury significantly, except for fruit heated 24 hours after drop-
ping. Waxing fruit alleviated the severity of skin injury, whether applied before or
after the heat treatment.^57 Impact bruising thresholds could be affected by delay after
harvest and temperature. In bananas, compression and impact bruising increased