Role of antioxidants in the preservation of fruits and vegetables.

Antioxidants control the oxidative deterioration of fruit and vegetable products. More
important In this respect: are those which are synergists and mostly acidic in nature.
Thiourea and ascorbic, sulphurous and citric acids have found Important uses in controlling
the oxidative discolouration of cut fruits and vegetable$ during their preparation (or freezing,
canning and dehydration. Thiourea, citric acid and sulphur dioxide are reported to act also
as stabllb:ers of vitamin C. Propyl gallate, tocopherol and NDGA have been reported as
specific inhibitors of peroxidase. Ascorbic acid has found a very wide application in the
frozen fruit Industry against dlscolouration and off-flavour developments. Prefreezlng treat.
ments employing sulphur dioxide in the form of sulphites have been found useful only in
small concentrations of the chemicals. Colour and nutritive constituents of dried fruits
and vegetables are retained satisfactorily by the use of sulphur dioxide and sulphites. The
problems of discoloration and flavour losses in juices have been overcome to a great
extent by the use of ascorbic acid and its isomers while citric acid has been reported to
enhance the stability of natural colours. In canned products also, ascorbic acid and its
Isomers prevent browning and development of oxidative rancidity in chips and nuts can he
satisfactorily prevented and their stability improved by the use of a number of phenolic
and other antioxidants.