Penetration and Retention of Methyl Bromide in Packaged Table Grapes

Abstract

The type of packing box had no effect on the initial penetration of methyl bromide (MB) into packed grapes (Vitis vinifera L.) during fumigation tests designed to control the Mediterranean fruit fly (Ceratitis capitata Wied.). However, when perforated paper or plastic wraps were placed around individual grape clusters during packing, penetration of MB was slowed during the first 10 minutes exposure, and MB concentrations in plastic wrapped grapes were near the minimal level required during the last half of the fumigation period. In tests using expanded polystyrene foam boxes (both packed with grapes and empty), MB concentrations consistently fell below the minimum level required (22 g/m³) at about the midpoint of the fumigation treatment, which indicated that large amounts of the gas were sorbed by the polystyrene. Subsequent measurements of MB taken after aeration for two hours showed that polystrene boxes desorbed MB, causing the concentration to increase to 1.0, 2.4, and 3.0 g/m³ in the resealed chambers after 0.5, 2, and 17 hours, respectively. Desorbtion of MB from the polystyrene boxes was three to four times as great as it was from wood Kraft veneer and fiberboard boxes. These high levels of MB could constitute a potential hazard to personnel working in and around commercial chambers, if adequate precautions were not taken to exhaust the gas.