Milk products in sparkling wine

Yves,

Skim milk (or casein) is a fining agent. It is used to remove phenolic compounds from the wine. These may give a harsh or flabby character to the palate, which the winemaker wants to remove. Fining agents are generally insoluble in wine, and they simply strip an undesirable character, then settle to the bottom of the tank as solids.

It is generally believed by winemakers that there are no traces of milk left behind - in particular the proteins that might cause an allergic reaction. However, it is now known that galactose traces remain (milk sugar), and because current analytical methods may not be sophisticated enough to pick up low levels of proteins, the labelling regulations now require it to be mentioned.

It is a very common fining agent, and has been used for many years - the only difference is that the label must now mention it if it was used. Milk is actually fairly innocuous, when you consider that ox blood used to be a common fining agent! Milk is legal in Australia, but I cannot speak for any other countries - I would be surprised if it was illegal though, along with isinglbutt, gelatine, and other fining agents.