Should butter be kept in the fridge or on the counter?

The reason butter can sit out at all is that it is about 80 per cent fat and only 16 per cent water, and that water is locked in tiny droplets that bacteria struggle to colonise. What does happen is oxidation: the fat reacts with oxygen and light and goes rancid, which is a chemical change rather than a microbial one.

Step by step

1. Decide by how fast you get through it.A block that will be finished within a week can live in a covered dish on the counter. A block that will take a month should be in the fridge, and a bulk buy should be in the freezer. Storage follows use, not rules.
2. Cover it, always.Air and light drive rancidity, and butter also absorbs smells readily — an open block in the fridge next to onions will taste of onions within days. A lidded butter dish, a French butter crock or foil are all fine; an uncovered dish on the worktop is not.
3. Keep the counter block small.Cut off what you need for the week and refrigerate the rest. A whole 250g block sitting out for three weeks is where rancidity actually happens.
4. Take the kitchen temperature seriously.Below about 20°C, butter keeps well on the counter for a week or so. Above that it softens, oils out and goes rancid faster. In a hot kitchen or a heatwave, the fridge is the only answer.
5. Prefer salted butter for the counter.Salt suppresses microbial growth in the water phase, so salted butter is the more forgiving one to leave out. Unsalted is better refrigerated and used faster.
6. Wrap it properly in the fridge.Foil or the original wrapper, then in a box if the fridge has strong smells in it. The butter compartment in a fridge door is the warmest place in the appliance, which is fine for butter and bad for almost everything else.
7. Freeze the surplus.Butter freezes very well, in its wrapper inside a freezer bag, for around three months for unsalted and longer for salted. Thaw in the fridge overnight, or grate it straight from frozen into a recipe.
8. Recognise rancid butter.A sharp, waxy, crayon-like or cheesy smell, a darker yellow crust on the cut faces, and a bitter taste. Rancid butter will not make you ill in any dramatic way but it tastes unpleasant and it will carry that taste into anything you cook with it.

Tips

• A French butter crock — butter packed into a lid that sits inverted in a little water — keeps butter spreadable and airtight without refrigeration. Change the water every couple of days.
• If you have kept butter too long and it smells slightly off, do not try to use it in baking. Butter is a large share of the flavour of a cake and rancidity comes straight through.
• Cut the exposed faces off a block that has been in the fridge uncovered for a while — the discolouration and smell absorption are usually only surface deep.
• Freeze butter in 50g portions if you bake occasionally. It saves cutting a frozen block and thaws in minutes.
• Butter kept for spreading and butter kept for cooking can be different things. There is no reason the good European-style block has to sit on the counter losing quality.

Common mistakes

• Leaving butter uncovered in a butter dish with no lid — Oxygen and light are the two things that make butter rancid, and an open dish supplies both continuously. The lid is not decorative.
• Keeping a month's butter on the counter — It is a slow, invisible decline rather than a sudden spoilage, so you notice it only when a cake tastes wrong. Keep a week out, refrigerate the rest.
• Storing butter unwrapped next to strong-smelling food — Fat absorbs volatile aromas readily. Butter stored beside cut onion, fish or a ripe cheese will taste of it, and the change is not reversible.

Questions people ask