Instabilities and problems from other metals

Other metals which have been associated with problems are aluminium and lead. Instability problems from these metals are extremely rare, and the few records available indicate that the removal of the opportunities for wine to contact these metals has virtually eliminated them as a source of contamination.

Aluminium

Although aluminium hazes are now almost unknown, it is wise to be vigilant and ensure that no equipment fabricated from, or containing, aluminium components, comes into contact with wine. The use of aluminium components in the building industry can lead to the mistaken belief that the metal is inert under all conditions. Any uncoated aluminium surface in contact with wine will corrode and cause contamination. In cases of severe contamination, instability in the form of a white haze will result. Very low levels of contamination by aluminium metal have been known to cause problems of reduced sulfur off-odours in the affected wine with no perceptible haze instability (Rankine 1989).

Bentonite has been recognised as a possible source of aluminium, although the amounts contributed to wines through bentonite fining appear to be insufficient to constitute a significant instability problem. The aluminium content of bentonites, like that of iron, should be a criterion on which the product is selected (Rankine 1989).

Lead

Lead has never been at a concentration in wine to give rise to an instability problem. In the recent past, there have been regulatory issues with regard to the levels of lead in wine and its affect on human health. Fortunately, these concerns have been largely put to rest through the discontinued use of tin lead capsules for bottle packaging. The primary source of lead in wine in Australia appears to be from the winemaking process rather than viticultural sources, and are discussed in Stockley et al. 2003.

REFERENCES:

Rankine, B.C. Making good wine—a manual of winemaking practice for Australia and New Zealand. Melbourne: Sun Books; 1989

Stockley, C.S.; Smith, L.H.; Tiller, K.G.; Aulson, B.L.; Osborn, C D’A; Lee, T.H. (2003) Lead in white wine: a case study of two varieties at two wineries in South Australia. Aust. J. Grape Wine Res. 9: 47-55.

Zoecklein, B.W.; Fugelsang, K.C.; Gump, B.H.; Nury, F.S. Wine analysis and production. New York, 1999.