Why does chocolate turn white? Bloom explained

You coat something in melted chocolate, put it in the fridge, and a day later the surface has gone dull with pale grey streaks. It looks like it has spoiled.

It has not. This is bloom, it is completely safe to eat, and it comes in two varieties that look similar but happen for opposite reasons.

Fat bloom — the common one

Pale, greyish, slightly streaky or marbled. Rub it and it feels smooth and may soften under your finger.

Chocolate is cocoa solids suspended in cocoa butter, and cocoa butter is fussy: it can crystallise into six different forms, only one of which gives that glossy, snapping finish. When chocolate gets warm — even just warm, not melted — some of that cocoa butter liquefies, migrates to the surface, and recrystallises there in a different, duller form.

What causes it:

• Temperature swings. Fridge to counter and back is the classic trigger.
• Melted chocolate that was never tempered. If you simply melted a bar and used it as a coating, it sets in unstable crystal forms and blooms readily. This is the usual cause in home kitchens.
• Storage somewhere warm, even briefly.

Sugar bloom — the gritty one

Also whitish, but it feels rough or sandy rather than smooth, and the surface looks dry rather than greasy.

This is caused by moisture, not heat. Water condenses on the chocolate's surface, dissolves some of the sugar, then evaporates and leaves the sugar behind as visible crystals.

The usual cause is taking cold chocolate straight out of the fridge into a warm kitchen. Condensation forms on the cold surface exactly the way it does on a cold drink.

Telling them apart

• Smooth and greasy to the touch, softens under a finger → fat bloom. Heat.
• Dry and gritty, sandy feel → sugar bloom. Moisture.

Fat bloom is far more common in home baking, because most of us melt chocolate without tempering it.

Is it still safe?

Yes. Bloom is a physical change in how the fat or sugar is arranged on the surface — nothing has gone off, nothing has grown, and no bacteria are involved. Bloomed chocolate is safe to eat.

What does change is texture and appearance. Fat bloom tastes slightly waxy and the snap is gone. Sugar bloom feels faintly gritty. Neither is pleasant to serve, but both are perfectly edible.

What bloom is not: mould. Mould on chocolate is fuzzy, usually coloured green, blue or black, and raised. Bloom is flat, and it is white or grey. If it looks furry, bin it.

Preventing it

Do not store chocolate in the fridge if you can avoid it. Cool, dry and dark — around 15–18 °C — is ideal. The fridge causes both kinds of bloom: temperature swings on the way out, and condensation on the surface.

If the fridge is unavoidable because your kitchen is hot, seal it in an airtight container and let it come back to room temperature inside the container before opening. The condensation then forms on the box, not on the chocolate.

Keep it away from strong smells. Cocoa butter absorbs odours readily, which is a separate reason the fridge is a poor home for chocolate.

For a coating that stays glossy, chocolate needs tempering — controlled heating and cooling that sets the cocoa butter into the right crystal form. A simpler route for home baking: stir ½ teaspoon of coconut oil into the melted chocolate. It will not give a true tempered snap, but it coats more evenly, sets faster and blooms less.

Can you fix bloomed chocolate?

Not on the surface — you cannot polish bloom away. But it melts back down perfectly well, so bloomed chocolate is fine for brownies, ganache, hot chocolate or any recipe where it is melted anyway.

For anything where appearance matters, start with fresh chocolate and store the finished item somewhere cool and dry rather than in the fridge.