Agriculture Reference
In-Depth Information
Table 20.8.
Cooling methods for temperature management of fresh horticultural commodities.
Cooling Method
Variable
Ice
Hydro
Vacuum
Forced Air
Room
Cooling times (hours)
0.1-0.3
0.1-1.0
0.3-2.0
1.0-10.0
20-100
Water contact with product
Yes
Yes
No
No
No
Product moisture loss (%)
0-0.5
0-0.5
2.0-4.0
0.1-2.0
0.1-2.0
Capital cost
High
Low
Medium
Low
Low
Energy efficiency
Low
High
High
Low
Low
Source: USAID (2006).
harvest, sorting, packing, and transport play a crit-
ical role in minimizing the potential for microbial
contamination of fresh produce.
There should be air spaces in storage cold rooms be-
tween pallets and walls to ensure proper circulation,
while transit vehicles should be cooled before loading
the fruits (FAO, 1989).
2.
Postharvest treatments designed to minimize produce
contamination and maximize quality.
Adequate concentration of sanitizer is maintained in
water to kill microbes before they attach or become in-
ternalized in the fruit. This is particularly important in
postharvest procedures involving water, including wash-
ing, cooling, water-mediated transport, and postharvest
drenching in chemicals (USAID, 2006).
Transpiration or evaporation of water from the plant
tissues is one of the major causes of deterioration of
lemon and lime fruits after harvest resulting in direct
quantitative losses (loss of salable weight), as well as
losses in appearance (wilting, shriveling), textural qual-
ity (softening, flaccidity, limpness, loss of crispness and
juiciness), and nutritional quality. Water loss as a phys-
ical process can be controlled by various postharvest
treatments such as waxing applied to the fruit (surface
coatings and other moisture barriers), packaging in poly-
meric films that act as moisture barriers, or careful han-
dling to avoid physical injuries or manipulation of the
environment (maintenance of high relative humidity).
The use of postharvest fungicides and growth reg-
ulators such as GA or 2,4-D is common to delay
senescence of lemon and lime (USAID, 2006). Ac-
ceptable disinfection treatments including ionizing ra-
diation are also used. Disinfestation treatments include
certificate of insect-free, areas, use of chemicals (e.g.,
methyl bromide, phosphine, hydrogen cyanide), cold
treatments, heat treatments, and some combination of
these (Ladaniya, 2008). Selection of methods depends
on cost and efficacy of that treatment against the in-
sects of concern with least potential damage of the fruit
(USAID, 2006).
Dipping lime in hot water (50
◦
-53
◦
C for 2-3 min) and
removal of ethylene from lime storage facilities can be
beneficial in retarding loss of green color and delaying
decay incidence. Ethylene causes limes to lose their
green color and unmask their yellow pigments, which is
desirable for marketing green limes (Arpaia and Kader,
2000).
3.
Postharvest treatments designed to manipulate the en-
vironment around produce to enhance quality.
Adequate O
2
levels are required to maintain aerobic res-
piration, however, the precise level of O
2
that reduces
respiration while allowing aerobic respiration varies
with fruits. A combination of 5-10% O
2
and 0-10%
CO
2
retards senescence (loss of green color) of limes;
however, this is inadequate for decay control. Expo-
sure above 10% CO
2
and/or less than 5% O
2
can result
in scaldlike injury, decreased juice content, off flavors,
and increased susceptibility to decay. Commercial use
of controlled atmosphere (CA) on limes is very limited
(Arpaia and Kader, 2000). At higher temperatures, the
demand for ATP may exceed the supply; hence anaero-
bic respiration will be promoted. Therefore the need for
adequate O
2
should be considered in selecting the var-
ious postharvest handling procedures such as waxing,
film wrapping, and packaging.
MINIMALLY PROCESSED AND FRESH-CUT
PRODUCTS
Trends in the values of consumers are strongly influenc-
ing the food market trends. Consumers demand freshlike,
minimally processed foods without artificial additives and
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