Improved Fumigation Process for Stored Foodstuffs by Using Phosphine in Sealed Chambers Andrea Formato, † Daniele Naviglio,* ,‡ Gian Pio Pucillo, † and Giorgio Nota ‡ † Department of Agricultural Engineering, University of Naples Federico II, via Universita ̀ , 100, 80055 Portici, Naples, Italy ‡ Department of Food Science, University of Naples Federico II, via Universita ̀ , 100, 80055 Portici, Naples, Italy ABSTRACT: In this paper we present an innovative device designed and constructed to improve the fumigation process for stored foodstuffs with the use of phosphine gas in sealed chambers. The device allowed a considerable reduction in phosphine production time (from about 5 to 7 days for traditional systems to 2 days for the equipment considered), maintaining the system below the inflammability threshold, and at the same time achieving the total exhaustion of aluminum (or magnesium) phosphide so as to avoid toxic residues at the end of the process. With the standard device currently available on the market, after the normal 5-7 day fumigating period, the powder residue contains as much as 1-2% (w/w) of phosphide. Thus the residues, according to current legislation, have to be considered toxic and harmful. To overcome this disadvantage, appropriate modifications were made to the cylindrical tray used for the fumigation process: a nebulizer was installed, which has the function of increasing the moisture of the air spreading around the phosphide pellets and allowing a more rapid reaction with phosphide. Moreover, the cylindrical tray was also heated by means of an electrical resistance, and temperature was checked by a thermostat, so as to always obtain the same efficiency, independently of outside temperature, for both hot and cold periods, since reaction speed depends on the system temperature considered. In addition, a control device for air saturation allows condensation processes to be avoided. Using the modified cylindrical tray we performed tests to determine the best values of humidity and temperature for the process concerned, avoiding phosphine concentrations that might result in a fire hazard, and the remixing of phosphide pellets inside the cylindrical tray. Our experimental data allowed us to obtain a mathematical model used to gain an insight into the process in question. KEYWORDS: fumigation, phosphine, foodstuffs, aluminum phosphide, magnesium phosphide ■ INTRODUCTION Warehouse-stored agri-food products awaiting retail placement may undergo chemical, physical and microbiological changes and also be infected by insect pests. The latter is a very frequent event which, once started, may cause the total loss of quality of the food product. Once the infesting parasites proliferate inside the storage areas, the contaminated foodstuffs experience significant loss of value, due to loss of weight and nutritional content. Insects are also a vehicle for the propagation of molds and mycotoxins, insofar as, if allowed to proliferate inside food products, they contribute to a further increase in temperature, triggering oxidizing processes and microbiological contami- nation (molds and bacteria) that can give rise to the development of metabolites such as mycotoxins. Further, for the above reasons, the use of preventive measures to combat pests becomes of fundamental importance with a view to ensuring proper food storage. 1-4 In such foods, each chemical process has to be documented and traceable, as required by recent regulations, to avoid the risk that there may be traces of potentially harmful chemicals for consumer health. 5 In the case of the fumigation process with phosphine gas, it should be noted that inhalation of phosphine may cause severe pulmonary irritation leading to acute pulmonary edema, cardio- vascular dysfunction, coma and death; gastrointestinal disor- ders, renal damage and leukopenia may also occur. Further, exposure to 1400 mg/m 3 (1000 ppm) for 30 min may be fatal for animals and humans. Ingestion of phosphides, particularly aluminum and zinc phosphides, may induce severe gastrointestinal irritation leading to hemorrhage, cardiovascular collapse, acute neuropsychiatric disorders, and respiratory and renal failure within a few hours. Hydrogen phosphide or phosphine (PH 3 ) formulated in 0.6 or 3 g tablets or pellets of aluminum or magnesium phosphide are indifferently used in a ratio of 12 to 15 g per ton of foodstuff. This chemical is still one of the most widely used products for disinfestation during storage both in Italy and the rest of the world. 6-11 This is thanks to a certain safety in usage (delayed development) and its physicochemical characteristics (smell threshold lower than the danger threshold, equilibrium in terms of air density), and its high effectiveness in combating insect pests. 12,13 Traditional fumigation techniques using phosphine gas still involve the manual introduction of tablets with the aid of probes by staff equipped with appropriate protective devices in storage areas. At the end of the fumigation process, the operators reopen the areas and start the recovery phase which lasts at least 48 h. The phosphine required for fumigation is generated slowly by the reaction of magnesium or aluminum phosphide with ambient humidity. As it is highly toxic, phosphine can easily kill eggs, larvae and insects by asphyxiation in low concentrations. 14-16 Moreover, phosphide pellets contain delaying chemical compounds that develop inert gases like ammonia and Received: August 11, 2011 Accepted: December 1, 2011 Published: December 1, 2011 Article pubs.acs.org/JAFC © 2011 American Chemical Society 331 dx.doi.org/10.1021/jf204323s | J. Agric.Food Chem. 2012, 60, 331-338