What is Chocolate Bloom?
Chocolate bloom is a pale, dusty, or streaky coating that can appear on the surface of chocolate over time. It comes in two forms: fat bloom, caused by cocoa butter separating out and rising to the surface, and sugar bloom, caused by moisture dissolving sugar on the surface, which then recrystallises as it dries. Both are harmless changes in appearance and texture, not spoilage, and chocolate with bloom remains safe to eat. Bloom is also the answer to a common worry: “Why does my chocolate look mouldy?” Actual mould is rare in chocolate generally, and rarer still in dark chocolate specifically, since its low moisture content and higher cacao percentage make it a poor environment for mould to grow.
In More Detail
An untempered block of chocolate in storage at MayHawk showing signs of chocolate bloom after being left to cool naturally.
What causes fat bloom?
Fat bloom happens because cocoa butter isn’t a single, fixed substance, it’s a mix of different fats with slightly different melting points, and it can settle into six different crystal structures once it cools. Chocolate is tempered specifically to lock the cocoa butter into one of those structures, Form V, which gives it a glossy, stable finish. Left long enough, or exposed to warmth, that structure slowly shifts toward a different, more stable form, and as it does, some of the fat migrates to the surface and re-hardens there as a pale film. This is the same crystal behaviour covered in full in What Does Tempered Chocolate Mean? and in Cocoa Butter Crystal Structure.
What causes sugar bloom?
Sugar bloom has a different, simpler cause. If chocolate is exposed to moisture, from condensation, humidity, or coming straight out of a fridge into a warm room, that moisture dissolves some of the sugar sitting at the surface. As the moisture evaporates again, the sugar recrystallises, leaving a rougher, sometimes gritty texture rather than the smooth film fat bloom produces.
How can I tell bloom from mould?
Four checks reliably separate the two.
| Bloom | Mould | |
|---|---|---|
| Texture | Flat, smudges like powder | Raised, fuzzy or fibrous |
| Colour | White or grey only | Green, black, blue, or pink |
| Smell | None | Musty or sour |
| Location | Spread evenly across the surface | Isolated patches, usually on a filling or inclusion |
If a bar shows a raised, fuzzy, or oddly coloured patch rather than an even, flat film, that’s the point to stop and not eat it.
Why does MayHawk chocolate look so strange in the storage area?
One of the questions we’re asked most often by visitors to the Chocolate Studio is why the large blocks of chocolate stored on our production shelves look so strange. Some people look closely at the pale streaks and patterns across the surface and ask whether the chocolate is going mouldy.
It isn’t. What they’re seeing is fat bloom. As explained in What Does Tempered Chocolate Mean?, the cocoa butter naturally present in chocolate can form several different crystal structures, and careful tempering encourages one of them, Form V, to dominate.
Our stored chocolate hasn’t been through that process yet. After grinding and conching, we pour the liquid chocolate into large, deep trays and let it cool and solidify naturally. At this stage we aren’t making a finished bar. The chocolate is deliberately left untempered while it solidifies and matures.
Without that controlled crystallisation, the cocoa butter settles into a mixture of structures instead of one. Over time, some of it migrates to the surface and recrystallises there, creating the pale streaks, swirls and patterns known as fat bloom. It’s perfectly normal, and it’s not mould.
We’ve always found it rather fascinating, if we’re honest. The way the cocoa butter crystallises can produce genuinely striking patterns across the surface, sweeping streaks, crystalline textures, pale marbling that looks almost deliberate, and the exact formation depends on small changes in temperature, cooling speed, and the character of the chocolate itself.
These blocks will eventually be melted and tempered properly before becoming finished MayHawk chocolate, and the bloom disappears completely once that happens. But until then, we rather enjoy looking at it.
Why does dark chocolate resist mould better than milk or white?
Mould needs moisture to grow, and chocolate generally doesn’t offer much of it, which is the main reason mould on chocolate is rare at all. Dark chocolate goes further still: it carries less moisture than milk or white chocolate, neither of which is diluted by milk solids, and it holds a higher concentration of the natural compounds found in cacao, some of which have a mild inhibiting effect on microbial growth. Milk and white chocolate, and any chocolate with a moist filling or inclusion, are more hospitable environments by comparison.
Why does craft chocolate sometimes show bloom?
Bloom is more likely to slowly appear in high-quality craft chocolate, given enough time, because this type of chocolate usually contains no emulsifiers, food additives, or stabilisers like lecithin. With nothing artificial actively suppressing the crystal structure from shifting over time, craft chocolate can develop bloom more readily than industrially made chocolate. MayHawk chocolate contains no stabilisers or emulsifiers of any kind, so a natural bloom can appear given long enough or the wrong storage conditions. It isn’t a sign of a fault. It’s a consequence of a short, natural ingredient list, nothing more.
How can bloom be prevented?
Bloom is almost always a storage issue rather than a manufacturing one. Keeping chocolate at a stable temperature, away from sunlight, heat, and humidity, is the single most effective way to prevent it. See How Should I Store Chocolate? for the full detail.