Fumigation of Natural Raisins with Phosphine

Excerpts from the report: Raisins may be infested with insects at the time they are removed from the drying trays in the vineyards or they may become infested during storage. To eliminate the insect infestation, the raisins are fumigated at the time they are placed in storage and at intervals while in storage. During the past few years, phosphine has been used as a fumigant in the United States. It is manufactured in tablet and pellet form and is composed mainly of aluminum phosphide and ammonium carbamate. When exposed to the atmosphere, the tablets or pellets decompose to form phosphine (hydrogen phosphide), ammonia, carbon dioxide, and aluminum hydroxide. Phosphine is a gas that is slightly heavier than air, has an odor resembling carbide, and is effective against insects. Four tests were made to determine the effectiveness of phosphine against the most common insects that attack natural raisins stored in stacks covered with sisalkraft paper. The Food and Drug Administration has established a residue tolerance of 0.01 parts per million (p. p.m.) for the use of this fumigant on processed foods, one of which is raisins. Previous results with the type of treatments discussed in this study indicate that residues greater than 0.01 p. p.m. would not be expected.