Isothiocyanates in Wine

Allyl isothiocyanate is a contaminant used to protect the wine from the Candida Mycoderma yeast attack and to sterilize the air in wine storage containers. Illegal additions of methyl isothiocyanate to the wines are made to prevent spontaneous fermentations and are used as a soil fumigant for nematodes, fungi, and other diseases in fruit and vegetables (Saito et al., 1994 Gandini and Riguzzi, 1997). 

Determination of methyl isothiocyanate in wine can be performed by extraction with ethyl acetate and GC/MS analysis (Uchiyama et al., 1992). Spiked samples showed recoveries ranging between 83 and 90% in white wines, and 75 and 82% in red wines, with an LOD of 0.05mg/L. Also, analysis by direct injection using 1,4-dioxan as an internal standard was proposed (Fostel and Podek, 1992). 

Analysis of methyl isothiocyanate in wine also can be performed by headspace SPME-GC/MS using a CAR/DVB 65-pm fiber. A volume 

Anastassiades, M., Lehotay, S.J., Stajnbaher, D., and Schenck, F.J. (2003). Fast and easy multiresidue method employing acetonitrile extraction/par-titioning and dispersive solid-phase extraction for the determination of pesticide residues in produce, /. AOAC Int., 86(2), 412-431. 

Angioni, A., Garau, A., Caboni, P., Russo, M., Farris, G.A., Zara, S., and Cabras, P. (2005). Gas chromatographic ion trap mass spectrometry determination of zoxamide residues in grape, grape processing, and in the fermentation process,./. Chromatogr. A, 1097(1-2), 165-170. 

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Gandini, N. and Riguzzi, R. (1997). Headspace solid-phase microextraction analysis of methyl isothiocyanate in wine, /. Agric. Food Chem., 45, 3092-3094. 

Allyl isothiocyanate (CH2=CHCH2N=C=S) has been studied as a contaminant in wine from discs treated with this substance. It is used at the surface of tanks to prevent the development of yeast velum, which is prohibited in most countries. We did not find allyl isothiocyanate in any of the wines studied. 

Fostel, H. and Podek, F. (1992). Detection of methyl isothiocyanate (methyl mustard oil) in wine, Ernaehrung, 16(3), 157-158. 

Analysis of a sample from the hose pipe indeed showed the presence of benzothiazole and when the chromatogram of this sample was compared to that of the wine sample contaminated with this piping, there was a peak common to both of them. The mass spectra of the compounds found in the wine (Fig. 10.3) and of the sample from the hose were also similar. In both cases, from the library of reference spectra this compound has been identified as cyclohexyl isothiocyanate C6Hn-N=C=S and is a contaminant produced in the manufacture of rubber materials (Cocheo etal. 1983). 

Oil acts by extracting liposoluble substances. It is stirred vigorously to create an emulsion in the wine. This operation is repeated several times, until the oil is perfectly dispersed. When the mixture is allowed to rest, a layer of oil forms on the surface and is eliminated by careful racking. Liquid paraffin is mentioned in many books on this subject. It was not only recommended for eliminating unpleasant smells but also for isolating wine from the air in partly empty vats in order to protect it from acetic bacteria. In certain countries, solid paraffin discs, impregnated with allyl isothiocyanate, are used to create a sterile atmosphere. 

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