The Sorption and Retention of Ethylene Dibromide by Fumigated Citrus and Avocado Fruits

Abstract

Citrus fruits (Valeucias, navels and lemons) and avocados were fumigated in a gas-tight metal fumatorium (100 cubic feet capacity) with ethylene dibromide at dosages of 0.5 and 1.0 pound per 1,000 cubic feet. for a 2-hour exposure period at 70°F. The amount of ethylene dibromide sorbed by the commodities during fumigation was determined immediately after treatment. and thereafter at stated intervals for a period of 7 to 10 days. Under these experimental conditions lemons sorbed nearly twice as much ethylene dibromide as the oranges, but at the end of 7 days the amounts of ethylene dibromide retained by either the lemons or oranges amounted to approximately 1 p.p.m. Sorption curves for Zutano avocados and navel oranges show the varietal differences between these two fruits in that the avocados sorbed approximately five times that of the navel oranges but at the end of 7 days the navel oranges retained only a positive trace of ethylene dibromide, while the Zutano avocados, at the end of 10 days, retained more than 25 p.p.m. of the fumigant. Sorption curves on the peel and pulp separately show that the peel retained most of the ethylene dibromide sorbed by the fruit and only 3 to 4 p.p.m. penetrated to the edible pulp of either the lemons or oranges. After a 7-day storage period at room temperature, the concentrations of fumigant in the fruit had diminished to approximately 3 p.p.m. in the peel and to approximately 0.3 p.p.m. in the pulp. Experiments performed with macerated tissues of lemons, oranges and avocados to which known amounts of ethylene dibromide were added and allowed to stand at room temperature for 10 days, indicated that this fumigant is quite stable and nonreactive with the constituents of the tissues of these fruits.