Agriculture Reference
In-Depth Information
Preserving the ideal storage temperature in all sections of the postharvest
handling chains is vital for the quality and the shelf life of the product. When truck
or sea transportation is involved, temperature limits can be attained but the extended
transport time may be prohibitive for short-life products to reach all the available
markets. On the other hand, air transport offers limited transportation time but a
signifi cant transgression of temperature limitations is involved both during fl ight
and ground operations (Brecht et al.
2003
).
1.4
Gas Composition
MAP conditions are usually used to prevent microbial growth and ensuing spoilage.
CO
2
is used for this purpose either alone (in 100 % concentrations) or combined
with O
2
and N
2
and plays an important role in shelf life extension of the product by
preventing the growth of aerobic microfl ora (Puligundla et al.
2012
).
Oxygen is necessary for several processes that lead to quality degradation of the
product such as fat oxidation, browning and pigment oxidation. Furthermore an
atmosphere rich in O
2
favors the growth of all aerobic bacteria and fungi. Therefore,
to avoid any of these situations most of atmosphere modifi cations contain low
concentrations or absence of oxygen (Sandhya
2010
).
N
2
is an inert gas used for fi lling the additional space in the package to prevent
potential collapse. It has low solubility in water and lipids (Phillips
1996
).
CO is a gas not very soluble in water but with enhanced solubility in organic
solvents. Its use was permitted in the U.S. in packed lettuce due to its ability to
browning prevention. The very limited applications in the food industry are a result
of both its toxicity and its explosive nature (Sandhya
2010
).
1.5
Nature of the Product
The process in which organic materials (carbohydrates, proteins and fats) are
degraded into simple end products with simultaneous energy emission is called res-
piration. Through this process, CO
2
is a fi nal by-product and O
2
is consumed.
Respiration continues even after harvest and during storage, so it is crucial that each
type of vegetable interacts with the surrounding atmosphere and if the conditions
are not satisfactory, physiological disorder occurs (Workneh and Osthoff
2010
).
Ethylene (C
2
H
4
) is a plant hormone that signifi cantly affects the physiological
process of the plants. Storage temperature, injuries, disease occurrence and water
absence induce ethylene formation. Rapid ripening and increased respiration lead-
ing to shortened shelf life are directly affected by ethylene exposure. Specifi c pack-
aging conditions can lead to reduced ethylene formation and consequently to
prolonged shelf life (Irtwange
2006
).
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