If you have ever delved to the furthest corners of the kitchen cupboard and found a bar of embarrassingly out-of-date chocolate, it probably had a layer of what looks like speckled grey chalk on its surface. This is not in fact mold, but rather an indication that the chocolate has ‘bloomed’.
What is chocolate bloom?
Two types of blooming can occur: fat bloom and sugar bloom. Both relate to the conditions in which the bar was stored and the standard of its initial tempering.
As storage conditions are the most common cause of blooming, the discolouration can occur even when the chocolate is within its use-by date. As such, bloomed chocolate is perfectly fine to eat – it just won’t have the same pleasing melt and complexity of flavour as it once did.
For more information about how to correctly store chocolate, check out our article How to Store Your Chocolate.
Fat bloom is the most common type of blooming to affect chocolate, as it is caused by temperature changes during storage.
When chocolate is stored in too warm an environment (though not warm enough to melt it entirely), the fat within the chocolate (found in the cocoa butter) will melt, separate from the other ingredients, and come to the surface of the chocolate. This is the grey-white substance you can see in bloomed chocolate.
While this sort of blooming can happen to the very best chocolate bars, it is more likely to occur on chocolate that has been poorly tempered. If the chocolate is not sufficiently stable in crystal structure 5, the cocoa butter will find it easier to separate from the other ingredients. For a full education in tempering, read our article Tempering Chocolate: A Complete Guide.
Sugar bloom occurs when moisture reaches the surface of the chocolate, most often in the form of condensation (but sometimes due to melted ice packs!).
When moisture sits on chocolate, the sugar within the chocolate absorbs the water and dissolves. When the moisture eventually evaporates, the sugar forms larger crystals and sits on the surface of the chocolate, giving it a grainy feel and the grey-white blooming effect.
By appearance alone, sugar bloom is hard to distinguish from fat bloom. Both appear as a dusty, chalky layer of grey speckles on the surface of the chocolate. When feeling the chocolate, however, sugar bloom feels grainy and does not rub off to the touch, whereas fat bloom is soft and can be rubbed away.
How to prevent bloomed chocolate
By far the biggest cause of bloomed chocolate is inappropriate storage conditions. To prevent fat bloom, chocolate should be stored in a cool environment away from direct sunlight and avoiding extreme temperature shocks (which means not in the fridge!).
If making your own bars and chocolate treats, tempering the chocolate correctly before cooling and storing will help to prevent blooming.
To prevent sugar bloom, chocolate should be stored in dry conditions. This means in a dry cupboard (not the one above the kettle!) rather than in the fridge as refrigerators are naturally very moist environments.
If you live in a humid climate, the easiest way to prevent moisture reaching the bar is to wrap it very tightly in its packaging and place it in an airtight container. (Our Craft Chocolate Storage Pouches are perfect for the job!)
How to reverse bloomed chocolate
Blooming is no reason to throw away quality craft chocolate: it is still perfectly edible and can even be reversed.
If you are not gifting the chocolate and do not mind the slight difference in texture or the peculiar appearance of bloomed chocolate, the easiest solution to blooming is to ignore it and eat the chocolate regardless.
If, however, you are a true chocolate aficionado and have the equipment to make your own bars, melting down the chocolate and retempering it will remove the blooming and return the chocolate to its previous glory. To get your hands on a mould to make your own bar, follow this link.
Bloomed chocolate can also be used for cooking where it is likely to be melted down or mixed with other ingredients anyway. For some excellent chocolate recipes, check out the delights of our recipe page.