Lead in wine: a case study on two varieties at two wineries in South Australia

Abstract

Sources of lead in wine were inferred from systematic assay of grapes must and wine, during winemaking. Two Australian wineries were monitored during the 1994 vintage with respect to vinification of Riesling and Shiraz. Juice and wine samples were collected at several process stages from crushing through to bottling, and were analysed for their total lead concentration by graphite furnace atomic absorption spectrometry. Selected samples were subsequently analysed for lead isotope ratio (fingerprinting method) to infer possible sources of lead in samples. Lead concentration in fermenting must was found to vary during vinification. In particular, lead concentration increased significantly in open-top vessels, in holding bins and during pressing. Juice and wine stored in concrete or waxed wood also had a significantly higher concentration of lead compared to juice or wine stored in stainless steel. Moreover, fining with bentonite or filtering with diatomaceous earth contributed further to final lead concentration, while fermentation, both primary and secondary, removed lead Overall, wines processed via these different systems still contained only traces of lead, and generally less than 30 μg/L (30 micrograms per litre). These trace levels are of no concern to human health when such wines are consumed in moderation.