Residues and effects on the aroma profile of apples as result of phosphine fumigation

The fumigation of stored products is a common practice to control the infestation and prevent the spread of pests through international trade. The fumigants most frequently used for quarantine and pre-shipment (QPS) purpose are methyl bromide and phosphine. Based on the Montreal Protocol, the non-QPS use of methyl bromide was phased out by 2005 in developed countries and will be banned by 2015 in developing countries. Therefore, phosphine is increasingly being used as a replacement. Recently, apples are now being fumigated with phosphine prior to export to control eggs of the codling moth (Cydia pomonella). The present study addresses sorption and desorption behaviour of phosphine by apples under different conditions and the formation of residues. The impact of the initial fumigation concentration and of the storage temperature was analyzed. During the laboratory experiments phosphine concentration was monitored using GC-MS instrumentation. Furthermore, the possible impact of phosphine on the organoleptic quality of treated apples (Malus domestica Borkh., cv. ‘Braeburn’) was addressed. For this purpose a headspace solid-phase microextraction (HS-SPME) technique was used and coupled to subsequent gas chromatography-mass spectrometry (GC-MS). The apples were fumigated for 48 h with phosphine at 2,000 ppm. Following the fumigation procedure apples were aired and stored under controlled conditions. Samples for the analysis of the aroma profile were taken at day 0, 1, 2, 7, 10, 14, and 21 after fumigation. The apples were processed and subsequently analyzed by HS-SPME-GC-MS. The results obtained for the fumigated samples were than compared to untreated reference samples. It could unambiguously be demonstrated that phosphine fumigation qualitatively and quantitatively alters the organoleptic quality of treated apples. However, further research on all aspects discussed in this study is required.