Are crystals in wine safe?

Quick answer

Usually, yes. Most crystals found in wine are harmless tartrate deposits. They are naturally occurring wine salts, most commonly potassium hydrogen tartrate, also called potassium bitartrate. These crystals can form after the wine is bottled, particularly if it becomes cold.

Tartrate crystals do not automatically mean the wine is spoiled or defective. They may look like tiny shards of glass, however, so appearance alone cannot prove what an unfamiliar particle is. If the material is hard, sharp, glass-like, associated with damaged packaging or simply uncertain, do not drink the wine. Keep the bottle, closure and particle if possible, then contact the retailer or producer.

What are the crystals?

Wine naturally contains tartaric acid and minerals such as potassium. Under some conditions, they combine and come out of solution as crystals. The usual result is potassium bitartrate, which may appear as clear, white or pale crystals in white wine, or darker crystals carrying wine colour in red wine.

Calcium tartrate is another possible deposit. It can form more slowly, sometimes well after bottling.

These deposits may settle at the bottom of the bottle, cling to the cork or appear in the glass. They can feel gritty, but typical tartrate crystals are considered non-toxic and generally harmless if consumed. Their main drawback is appearance and texture.

Why do crystals appear after chilling?

Tartrate is less soluble in cold wine. A bottle may be stored at room temperature, transported in cool conditions, placed in a refrigerator or chilled in an esky before serving. That change in temperature can encourage crystals to form or reveal instability that was not visible earlier.

This is particularly familiar with white, rosé and sparkling wines, which are often chilled before serving. Cold exposure does not turn a sound wine into a dangerous one; it can simply make naturally occurring deposits visible.

Winemakers may use cold stabilisation before bottling. This deliberately cools the wine so tartrate crystals form at the winery, where they can be separated from the wine. It reduces the chance of deposits appearing later, but it is not a guarantee that crystals can never form.

How should you handle them?

If the deposit looks like ordinary wine sediment and there are no signs of damaged packaging:

1. Stand the bottle upright for a short time.
2. Pour slowly into a clean glass or decanter.
3. Stop pouring before the settled material reaches the glass.
4. If a few harmless-looking crystals enter the glass, leave them behind or remove them for a smoother texture.

Decanting or careful pouring can separate a deposit. It does not make unsafe wine safe, and it should never be used as a way to deal with suspected glass or contamination.

When should you not drink the wine?

Do not taste-test a hard, sharp, glass-like or unidentified particle. Stop drinking and retain the bottle, closure, remaining wine and object if possible. A photograph of the particle and packaging may also help when contacting the retailer or producer.

You should be especially cautious if the bottle, rim or closure appears damaged, or if there is visible mould, an unusual surface film, leakage or another serious concern. These observations do not identify the problem with certainty, but they are good reasons not to consume the wine until you have advice.

In Australia, suspected foreign material such as glass can be reported to the relevant state, territory or local food authority. Food Standards Australia New Zealand advises consumers not to eat a product they are concerned about and to retain the original packaging and foreign object where relevant.

FAQs

Do wine crystals mean the wine is spoiled?

No. Typical tartrate crystals are usually a stability, appearance or texture issue rather than evidence of spoilage.

Are wine diamonds actually glass?

Usually, “wine diamonds” refers to tartrate crystals, not glass. But some tartrate deposits can resemble glass, so an unfamiliar or sharp particle cannot be identified confidently by sight alone.

Do crystals prove a wine is natural or unfiltered?

No. Their presence does not prove that a wine is natural, unfiltered or defective. It simply indicates that a crystalline deposit has formed.

Can I strain the wine?

You can carefully pour or decant a wine to leave ordinary sediment behind. Do not rely on straining to make wine containing suspected glass, contamination or another unknown foreign object safe.