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Every vegetable undergoes metabolism. That means that
every fruit is alive and breathes, consuming oxygen, not
only while growing, but also after harvest. The respiration
process can be described as the breakdown by oxidation
of carbohydrates such as starch, sugars and acids, which
are present in the vegetable tissues. The products of
respiration are heat, carbon dioxide, water vapour and
some aromatic compounds.
The
higher the rate of respiration of a fruit, the more rapid
will be its senescence and deterioration with a subsequent
reduced storage life. For a long time, refrigeration was
the only method used to store fresh fruit and vegetables.It
was not until 1821, biologist Berard discovered that the
metabolism of fruit and vegetables was slower when kept
at low oxygen concentration.
At
the beginning of the 20th century, it was through the
research of scientists KIDD and WEST, that C.A. storage
became a defined scientific subject. However, the real
commercial boom of C.A. took place simultaneously in Europe
and in the U.S.A. at the end of the '50s.
The
combined action of a lower concentration of oxygen and
a higher concentration of carbon dioxide in the storage
room considerably reduces respiratory activity. C.A.,
together with temperature reduction, has a greater effect
on the vegetables' metabolism by reducing, for example,
ethylene production of the fruit, by stopping the loss
of chlorophyll (green colour) and by delaying pectin hydrolysis
(maintaining flesh firmness), thus slowing the breakdown
of vitamins and acids.
From
a commercial point of view, this means not only preserving
the organoleptic qualities of the produce, but also reducing
losses due to pathogens (fungi) and to well-known physiological
disorders such as common and senescent scald and the appearance
of chilling injuries. These advantages become even more
evident when more elaborate techniques first applied in
Italy by Isolcell are used. We refer to the techniques
of "Rapid C.A." and "U.L.O.".
The
first consists in a very rapid reduction of oxygen in
the room (from 21 % to 5% in 36 hours). The U.L.O. atmosphere
(Ultra Low Oxygen) results in produce stored in an atmosphere
with an oxygen concentration of about 1 %.
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The choice of atmosphere depends on the type of produce
(commodity and variety) and on its physiological state
at the time of harvest. Compared to traditional C.A. storage,
the main advantages of U.L.O. storage are a further reduction
of the rate of respiration and metabolism (30%) and, especially
in the case of apples and pears, the control of some important
physiological disorders such as scald, internal breakdown
and maintenance of flesh firmness, thus leading to longer
shelf-life.
Recently
a new storage technique has been developed. Called “dynamic”
technique, it is based on a further reduction of oxygen
in the storage room until the fruit reaches its tolerance
limit.
To
get this result ISOLCELL ITALIA has developed very sophisticated
equipment such as the Intelligent Carbon Dioxide Scrubber
(IS).
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