How to store chocolate

Cool — 15–18°C is ideal, and stability matters more than the exact number. Dry — humidity below about 50%, because moisture causes sugar bloom. Dark — light degrades fats and accelerates rancidity. Sealed — cocoa butter absorbs odours readily. And away from strong smells, which is the same point stated as a practical instruction.

A cupboard away from the oven meets all five in most homes.

A domestic fridge is around 4°C and, more importantly, humid. Chocolate stored there absorbs moisture and picks up the smell of everything else inside, and when taken out it draws condensation that dissolves surface sugar into a rough bloom.

If the alternative is a 30°C kitchen, the fridge is the lesser evil — but wrap the chocolate airtight and let it come back to room temperature still sealed, so condensation forms on the wrapper rather than on the chocolate.

Dark chocolate keeps well for a year or more, and often longer — it has no water and little to spoil. Milk and white are shorter, typically six to twelve months, because milk fat goes rancid.

The date on a bar is a best-before rather than a use-by. Chocolate past it is not unsafe; it may have lost aromatic character or developed a stale note, particularly in milk and white.

The grey-white film on old chocolate is fat bloom — unstable cocoa butter crystals converting to more stable forms and migrating to the surface. Sugar bloom, from moisture, is rougher and grittier.

Neither is mould and neither is dangerous. The chocolate has lost gloss and snap and some texture, and it is perfectly usable for baking or melting, where the appearance is irrelevant.