Red wine deposits

I often receive e-mails from wine lovers asking why there are deposits in red wine bottles and why, as winemakers, don't we just take them out before bottling. I drafted the response below to one such e-mail and thought I would post it for others to read........


"You have received a gift from the wine gods!

The sediment you have noticed in the bottom of your bottle of Miamba Shiraz has been formed by a series of chemical reactions that have taken place after bottling. No matter how good a winemaker I am there is little I can do to prevent the formation of these deposits short of over purifying the wine you are drinking.

I’ll explain further…..

Firstly, the sediment is harmless, it doesn’t taste too good and it makes your wine a little “crunchy” if you get a mouthful of it however it will do no harm to your health. Actually the complete opposite is in fact true, the deposits are a rich source of antioxidants. They also have significant anti-bacterial properties and, believe it or not, can be used as pigment dyes (when dissolved with organic polymers) or even used for disinfecting skin when applied topically.

So you can see why I refer to them as a gift from the gods!

The chemistry of their formation is not difficult. It simply starts with the formation of potassium bitartrate crystals (KHT) formed through the reaction of the potassium ion (K+) extracted from the skins of grapes and the bitartrate ion (HT) from tartaric acid, a naturally occurring acid in grapes (we also use Tartaric acid as an addition to alter the pH/acid balance of the wine).

The potassium bitratrate is a colourless crystal. You may have seen a few of these crystals in bottles of white wine, often firmly attached to the bottom of the cork.

The potassium bitartrate crystals, when formed in red wine, become a nucleation site for tannin and anthocyanin complexes, the colour pigments in red wine. These complexes are relatively stable compounds however over time they grow into enormous molecular weight compounds and become insoluable in wine. They attach themselves to the bitartrate crystals to form a red wine “crust”.

The simplest way for a winemaker to avoid the formation of these deposits in wine is to put the wine through a cold stabilization process. We do this with all white wines, removing the bulk of the excess KHT through this process, by chilling the tanks to -5 deg C then filtering out the excess KHT crystals formed in the wine. This reduces the incidence of KHT crystal formation in white wine bottles, although often does not eliminate it completely.

We could do the same to red wine, and many commercial red wines are cold stabilized, however the process changes the structure, colour and character of the wine considerably. We believe that the disadvantages outweigh the advantages when it comes to our red wine and so have chosen to not cold stabilize our red wines. The trade off is a better quality red wine with the potential to “throw a crust”.

If you see sediment in a bottle of red wine and you would prefer to keep it out of your glass there are a couple of things you should do. First, simply stand the bottle upright for a few hours (or days) prior to pulling the cork or opening the screw cap, this will give the crust plenty of time to settle to the bottom of the bottle. You could then take this process one step further by decanting the wine prior to serving. There are a couple of good reasons to decant wine, it will stop your wine from becoming “crunchy” with sediment but it will also incorporate some air into your wine allowing your wine to “breathe” . I won’t go into the benefits of “breathing” your wine here, short of saying it’s a good thing if you want to get the best from your bottle of red wine."


Quite simple really......happy drinking!