Ask Jim: Bottle sludge, a good sign?

By Jim Chatto
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Leading young winemaker, Jim Chatto

Leading young winemaker, Jim Chatto


Dear Jim,
My husband came home with a case of red wine that he got for $50 from a mate at work, but all the bottles have a thick black silt in the bottom of them. My husband says it’s a sign of a good wine (for $50!!). They are a 2001 Cab Sav Merlot from Adelaide Hills - are they okay to drink and what is this gunk?
MSlemier, WA


It is true that reds wines can throw a silt or sediment as they age in the bottle. However, it would be very brave person to credit this as a measure of quality.

Most sediment in red wine occurs over a very long period, five to 50 or more years, and results primarily from the polymerisation (binding together) of phenolic compounds such as tannins and colour molecules. As these polymers become larger they are less soluble and thus fall out of solution forming a sediment. The result is a softening of the wine as larger tannin molecules tend to be less astringent than their smaller counterparts and the tannins that precipitate do not contribute to astringency at all.

However, there can be other reasons for sediment in the bottle, especially in relatively young wines, which are more sinister indeed. This type sediment can occur from the growth of micro-organism such as yeast and bacteria leading to undesirable characters in the wine such as volatile acidity or VA (mentioned in a previous column, see related links below) spritz or fizziness, as well as many other off taints.

I would be very sceptical of a young and especially cheap red wine with any kind of sediment. The alcohol content in wine, typically 12 to 15 percent in reds, is more than sufficient to kill off any microbes that may harm humans, so I would expect it is safe to drink - though your palate may not thank you.

That said if it tastes good then you have got a bargain! I would recommend decanting it prior to serving.



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