How long can ice cream sit out?

Ice cream should sit out for no more than about 10 to 15 minutes if you want to put it back in the freezer without hurting its texture. Once it has melted, treat it like any other perishable dairy food: eat it or put it in the fridge within two hours, or within one hour on a hot day above about 32°C. Melted ice cream that has been warm for longer than that should go in the bin.

Two clocks start when a tub leaves the freezer: one for quality, one for safety. Here is how to watch both.

Two questions: quality and safety

Ice cream that sits out loses quality long before it becomes unsafe. A few minutes on the bench softens the edges; a couple of hours on a warm table turns it into a sweet dairy liquid that bacteria are happy to grow in.

Frozen ice cream is very stable. Kept at -18°C or colder, the consumer guideline referenced in a freezer survey report prepared for the NZ Food Safety Authority, bacteria can't grow in it. The trouble starts once it warms up and melts. At that point it is milk, cream, sugar and, in a custard-based ice cream like ours, egg yolks: exactly the kind of food that needs to be kept cold.

How long before ice cream starts to melt?

A tub on the kitchen bench will start softening at the edges within minutes, and how quickly it goes from soft to soupy depends on the room, the sun and the size of the tub.

Things that speed up melting:

• Sun. Direct sunlight warms a tub far faster than shade, even on a mild day.
• Small portions. A scoop in a bowl has more surface for its size than a full tub, so it melts quicker.
• Warm surfaces. A bench next to the oven or a dark outdoor table soaks up heat.

If you only want it soft enough to scoop, five to ten minutes out is usually plenty. Our guide to softening ice cream has gentler methods that don't risk the edges melting, and a slightly softer scoop is less likely to give you brain freeze.

The two-hour rule for melted ice cream

Once ice cream has melted, follow the same rule as other perishable foods: don't leave it out of the fridge for more than two hours in total. In hot weather the window is shorter.

The idea comes from how quickly bacteria grow between 5°C and 60°C. Food Standards Australia New Zealand's 2-hour/4-hour rule, written for food businesses handling chilled food, says food out of refrigeration for under two hours can go back in the fridge, food out for two to four hours should be used and not returned to the fridge, and food out for longer than four hours should be thrown away. For home leftovers, Love Food Hate Waste NZ, citing Ministry for Primary Industries guidance, says to get food cooled and into the fridge within two hours.

Hot days need extra care. US Department of Agriculture advice, quoted by the University of Nebraska–Lincoln food safety team, is not to refreeze food left out of the fridge for longer than two hours, or one hour when it is above 90°F (about 32°C).

Can you refreeze ice cream that has sat out?

You can refreeze ice cream that is still cold and only soft at the edges. Don't refreeze ice cream that has fully melted, especially if it has been warm for a while.

There are two reasons. The first is safety, covered above: freezing pauses bacteria but doesn't kill them, so anything that grew while the ice cream was warm is still there when it thaws again. The second is texture. Ice cream is smooth because its ice crystals are tiny. When it melts and refreezes slowly in a home freezer, those crystals grow bigger and the ice cream turns grainy and icy.

To give a softened tub the best chance, smooth the top flat, press a sheet of baking paper onto the surface, put the lid on and set it at the back of the freezer, not in the door. Our full guide to storing ice cream explains why that helps.

Keeping ice cream cold at parties and on hot days

The simplest rule at any gathering is to keep the tub out for as little time as possible. Scoop, then put it straight back in the freezer or a chilly bin.

• Serve in batches. Bring out one tub at a time and swap it when it gets soft.
• Pre-scoop. For a crowd, scoop balls onto a lined tray, freeze them, then bring them out a tray at a time.
• Use ice. Stand open tubs in a bigger bowl of ice, and keep the table in the shade.
• Chilly bin backup. Pack a chilly bin with frozen ice packs if the freezer is far away. A full chilly bin stays cold longer than a half-empty one.
• Dry ice for long events. It keeps ice cream frozen for longer, but handle it with gloves, never seal it in an airtight container, and keep the chilly bin somewhere ventilated.

Setting up a dessert table? Our sundae bar guide covers how to keep the ice cream cold while guests build their own, and our post on how much ice cream to buy for a party helps you avoid having more tubs out than you need. Bringing a tub home from the shops on a sunny afternoon is its own challenge; our guide to keeping ice cream frozen on the way home has the tricks.

What about dairy-free and other ice creams?

The same rules apply to dairy-free ice cream, sorbet-style treats and gelato. Once melted, they are all moist, sugary foods, and the two-hour limit still applies. That includes our oat-milk dairy-free range. With guests who have allergies, keep scoops separate so a melting tub doesn't carry traces into another. Our ingredients and allergens page lists what goes into each flavour.

Quick checklist: ice cream out of the freezer

• Still firm, edges just soft? Back in the freezer now.
• Soft all through but cold? Refreeze with baking paper on top, or eat it today.
• Melted, out less than two hours (one hour on a scorcher)? Use it now or chill it in the fridge.
• Melted and warm for longer than that? Throw it out.
• Out overnight? Throw it out.

Got another question about looking after your ice cream? Our FAQs cover the basics, and for the latest on where to find our ice cream this summer, follow us on Instagram and Facebook.