How long do sweets last?

Sweets keep for a long time compared with most foods. They are mostly sugar with very little free water, and microbes such as mould need water to grow. But keeping safe is not the same as staying nice. Every kind of sweet changes as it ages, and each changes in its own way.

The best guide is the date

Most packed sweets carry a best before date. The government's guidance is that after that date, food is usually safe to eat but may not be of the same quality, and that poor storage can reduce quality before the date: see do sweets go out of date?

Jelly sweets and gums

Water moves from damp places to drier ones. A food with more water than the air around it slowly dries out, in the same way that salami dries in dry air. Jelly sweets and gums left open to the air lose moisture and firm up: see why do jelly sweets go hard?

Jellies set with starch have a second way of ageing. As cooked starch cools and sits, its molecules slowly line up again and recrystallise, which makes a starch gel harder. This process, called retrogradation, is the same one that makes bread go stale, and it happens much faster between minus 8 and 8 degrees Celsius, the temperature of a fridge.

Boiled sweets and rock

Hard sweets work the other way round. They are nearly 100 per cent sugar with almost no water, and sugar is hygroscopic: it pulls moisture out of the air. Left unwrapped, especially in a damp kitchen, boiled sweets and rock go tacky on the outside and can soften and stick together: see why does seaside rock go soft?

Chocolate

Chocolate can develop a whitish coating called bloom. Fat bloom comes from the fat in the chocolate slowly moving to the surface, and generally arises with storage or age. Sugar bloom comes from moisture, such as condensation, dissolving sugar on the surface, which then dries into a dusty layer. Either way, bloom spoils the look and feel of chocolate but does not limit its shelf life, and bloomed chocolate is still safe to eat.

Sherbet and fizzy sweets

Sherbet fizzes because an acid and a base react when they get wet. In the packet, that reaction waits for moisture, so sherbet needs to be kept dry: once damp, the fizz has already started: see what is sherbet made of?

Signs a sweet is past its best

Look for jellies that have turned tough, boiled sweets that have gone sticky or fused together, and chocolate with a white or grey film. These are signs that the sweets are past their best, and they will not taste as good. As with any food, if anything looks, smells or tastes wrong, throw it away.

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