Besides the obvious means of preservation for fresh fruit and vegetables, which concern the atmosphere in which the products are stored, i.e. the temperature and relative humidity, some fruit afford post-harvest preservation with the use of chemicals.
Thus, citrus are preserved for longer periods when coated with special waxes in liquid form, which formulate a film around each fruit preventing moisture loss and wilting. The citrus coating waxes are also an excellent medium for dissolving fungicides and application thereof on citrus fruit.
Equally important is the prior washing of the fruit with special detergents. That’s because this task both removes potential contaminants from the fruit surface, and also opens the pores allowing better adhesion of citrus coating wax and enabling skin penetration by fungicides.
Regarding grapes, the application of sulfur dioxide to protect them from fungal infections (especially Botrytis (gray rot)) is a common practice and a prerequisite for maintaining quality.
For best results, fumigation with sulfur dioxide vapor is performed within 12 hours hours after harvesting. This is imperative in cases where pre-cooling is slow and favors the germination of fungal spores in the presence of hot and humid air around the grapes.
Due to sulfur dioxide toxicity and the minimum quantity that should be present on grapes at the time they reach the consumer (value < 10ppm has been internationally established as the minimum acceptable sulfites threshold for table grapes), special precautions are taken to protect the packing facility personnel, and to prevent both damage from excessive doses of sulfur on grapes and the existence of residues of sulfur compounds on the grapes.
Hence, instead of applying sulfur dioxide by fumigation, grape guards (sulfur dioxide generating sheets) can be added in the packing boxes and crates, gradually releasing sulfur dioxide. HELLAGRO plastic grape guards are leading in the grape preservatives field.