quality compared to those made from raw materials even with short-term storage in
optimum conditions. The strawberries, currant, cherries, apricots, peaches for freezing
can be stored in refrigerating chambers for up to three days, grapes, plums - up to seven
days at a temperature from 0 to 6…7°C [8]. The foreign authors recommend to freeze
fruits and vegetables in 1.5 hours after they are harvested [9]. At the same time, under
conditions of harvesting at high temperatures, the fruits and vegetables should be
cooled to a temperature of 0 to 2º before freezing. With increasing storage temperature,
the intensity of heat dissipation increases, metabolic processes are accelerated, turgor
is lost, nutritional and biological value decreases, and weight loss increases. Different
cooling methods are used to slow down the metabolic processes: air, hydro- and
vacuum cooling. It is proved that it is expedient to carry out air cooing for small berries
and vegetables with a gentle consistence, hydrocooling - for fruits and vegetables of a
large size, vacuum cooling - for leafy vegetables. Air cooling is effective for all types
of fruits and vegetables, hydrocooling - for 62%, vacuum cooling - for 43%.
The modern technologies and methods of pre-treatment help to reduce unwanted
changes in the consumer properties of the frozen fruits and vegetables: loss of turgor,
changes in organoleptic properties. The existing methods of preliminary treatment,
regardless of the nature of the effect on the plant material (physical, chemical,
biochemical) can be conventionally grouped into two groups: those that are aimed at
inactivation of the enzymes and those that are aimed at reducing the activity of the
water.
The effective methods of inactivating enzymes of the plant tissues include
blanching (water or steam) and the treatment with chemical reagents. However, along
with the positive sides of blanching, namely, inactivation of the enzymes, partial
destruction of the vegetative forms of microorganisms, displacement of air from the
intercellular space and increased intensity of colour expression, decrease in the content
of pesticides and nitrates, it also should be noted disadvantages the main of which is
the loss of the valuable water-soluble substances, adsorption of water by the product,
the loss of tissue elasticity. Adding citric acid to water for blanching contributes to a
more intense decrease in the activity of the enzymes, as the pH and the threshold of
thermal denaturation of the enzymes are reduced. The colour stabilization is achieved
under condition of blanching in milk whey, addition to water for blasting of bisulfite,
metabisulfite, sodium carbonate, consistency - sugar and pectin with a low degree of
esterification [10].
In recent years studies have been conducted on the inactivation of the enzymes by
electroconductive method, infrared rays, high frequency currents.
The positive influence on the consumer properties of the fruits and berries has
been confirmed by preliminary treatment in solutions that have antioxidant properties:
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