Lemon and Lime - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 371

(A) Pitting of fruit in storage (B) Chilling injury (C) Blue mold

(D) Green mold (E) Sour rot (F) Brown rot

Figure 20.4. Postharvest physiological disorders and pathology of lemons and limes (source: Industry and
Investment NSW). For color detail, please see color plate section.

Mechanical injury
The high moisture content and soft texture of lemon and
lime fruits make them susceptible to mechanical injury.
This can occur at any stage, from production to retail mar-
keting, due to poor harvesting practices; unsuitable field
or marketing containers and crates with splintered wood,
sharp edges, poor nailing or stapling; overpacking or un-
derpacking containers; and careless handling during the
process of grading, transport, or marketing (FAO, 1989).
Injuries caused can take many forms, including internal
bruising, not visible externally, caused by impact and su-
perficial grazing or scratches affecting the skin and outer
layer of cells. Mechanical injury causes a substantial rise
in respiration, which induces a wide range of physiological
changes in adjacent, nonwounded tissue starting from the
site of injury. Important changes include enhanced respira-
tion, ethylene production, phenolic metabolism, and wound
healing (Baldwin, 1993; Mishra and Gamage, 2007).

Loss in quantity may occur where deep penetration of de-
cay often the result of infection in the field before harvest
makes the infected produce unusable. Loss of quality occurs
when the disease affects only the surface of the fruit caus-
ing skin blemishes that can lower the commercial value.
The fruit can become infected through injuries caused by
careless handling, by insect or other animal damage, or
through growth cracks; natural pores in the aboveground
and belowground parts of plants, which allow the move-
ment of air, carbon dioxide, and water vapor into and out
of the plant and by direct penetration of the intact skin of
the plant. Infection can occur in the field before harvest or
at any time afterward.
Postharvest diseases can be spread by field boxes con-
taminated by soil or decaying produce or both; contami-
nated water used to wash produce before packing; decay-
ing rejected produce left lying around packing houses and
contaminating healthy produce in packages (Kader, 2002;
Hardy, 2004). Table 20.6 outlines the postharvest diseases
affecting lemon and lime. Green mold is the most seri-
ous and common postharvest disease of citrus, even than
the blue mold, but blue mold grows faster. Blue and green

Postharvest pathology
Diseases caused by fungi and bacteria result in losses of
lemon and lime both in quantity and quality (FAO, 1989).