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FROM time to time the AWRI helpdesk takes an enquiry that goes something like this: “My wine was very difficult to filter via crossflow, what could be the cause?”

It’s a good question as most wines do fly through crossflow filters, primarily due to the way the continuous flow filter has been engineered.

It seems, however, that some wine components and instabilities can actually block or slow crossflow filters down and it’s the shape and size of the material that creates the blockage.

Both calcium tartrate crystals and polysaccharides can cause blockages or slow crossflow filters down.

Polysaccharides, whether they are acting alone or in combination with other colloids, can substantially increase the time required to crossflow filter a wine.

The best remedial treatment in this case is to use a suitable enzyme to break the polysaccharides down. A simple test that can determine if a wine contains high levels of polysaccharides is available on the AWRI website.

Another important point to note is that crossflow filters are not a replacement for membrane filters.

Yeast and bacteria can pass through crossflow filtration and later cause instability problems in packaged wine.

Winemakers planning to use crossflow filtration immediately prior to bottle are recommended to include a membrane filter in series after the crossflow to avoid microbial instability problems.

For further assistance regarding filtration difficulties or other winemaking issues, contact the AWRI helpdesk on 08 8313 6600 or winemakingservices@awri.com.au.