Which long-life milk keeps longest

Milk is the awkward one. Almost everything else in a long-life cupboard is obviously shelf-stable or obviously not, and milk comes in six or seven forms that all claim to keep and keep for wildly different lengths of time.

Here they are together, which is harder to find than it should be.

The table

Unopened, stored properly, from USDA FoodKeeper. Protein is per 100 ml as sold, or per 100 g for the powder, from CoFID 2021.

Two things in that table are worth more than the rest of this page.

UHT keeps for six months, not forever

This is the one that surprises people. A long-life carton sits on a shelf next to tins that keep for five years and looks like it belongs there, and FoodKeeper gives shelf-stable milk six to twelve months. We take the short end, as we do everywhere, because a shelf life is a floor you plan against.

It is not a failure of the process. Ultra heat treatment sterilises the milk and the carton keeps light and air out, but the milk inside is still milk: the fats oxidise slowly and the proteins keep reacting with the sugars, which is why an old carton tastes increasingly of cooked milk and eventually of cardboard. Nothing about it becomes dangerous. It becomes unpleasant.

If you are stocking a cupboard for longer than half a year, UHT is not the form to do it in.

Powder wins on every axis except taste

36 months, and 36.1 g of protein per 100 g against 3.3 per 100 ml for UHT. That is not a fair comparison as written, because one is a powder and one is mostly water, and that is exactly the point: you are carrying the water in every other row of that table.

A kilogram of skimmed milk powder makes roughly ten litres. Ten litres of UHT weighs ten kilograms and takes ten times the space, and it goes off six times sooner.

The catch is that it tastes like milk powder. In tea it is unobjectionable. In coffee it is fine. On cereal or in a glass most people notice immediately, and no amount of careful mixing fixes it. It is a cooking and hot-drink milk rather than a drinking one, and priced, weighed and dated as such it is the best thing in the table.

Mix it with a whisk or in a bottle you can shake, and let it stand for a few minutes. Powder stirred lazily into hot water is lumpy and tastes worse than powder that has been given thirty seconds of agitation and five minutes of rest.

Nobody publishes a figure for the plant milks

This is the genuinely odd finding, and we went looking for it rather than assuming it.

USDA FoodKeeper covers soya, almond and rice milk. For all three it gives no pantry figure at all: the only entries are “package use-by date” unopened, and seven to ten days refrigerated once opened. It treats them as chilled products, because in the United States they are largely sold chilled.

In Britain they are sold as ambient cartons, stacked on a dry-goods shelf beside the UHT. So the most-bought form in this country is the one the authority does not describe, and manufacturers publish a printed date rather than a duration.

We could have put a plausible number in. Twelve months would have looked right and nobody would have questioned it. There is no figure on those three ingredient pages, and there will not be one until somebody with standing publishes it.

What this means in practice: for plant milks, the date on the carton is not a rough guide that we can improve on. It is the only information that exists, and it is specific to that carton. Read it at the shop rather than at home.

Once it is open, none of it keeps

Every row in that table collapses to the same answer the moment you break the seal. UHT becomes ordinary milk and wants a fridge within five days. FoodKeeper gives opened soya and almond seven to ten days refrigerated. Evaporated and condensed are the same story in a tin.

This matters more on a trip than in a house, and it is the argument for powder all over again: powder is the only one where you open the packet and nothing starts running. You make up what you need and the rest is still a powder.

The exception is condensed milk, which is about 55 per cent sugar and preserved by it in the way jam is. It keeps far better than the others once opened, in a cool place, and it is the only tin in this list you can reasonably open on day one of a fortnight.

What we would actually carry

For a trip of any length: powder, with a small UHT carton if there is a tea drinker who will notice, and a tin of condensed milk for coffee and for pudding.

For a cupboard being stocked for a year or more: powder and evaporated. Both carry their weight, both keep, and evaporated milk is the one that makes porridge and semolina worth eating.

UHT is for the first month, not for the back of the cupboard. It is the best of these to drink and the worst of them to store, and treating it as a long-term staple because the carton says long life is the mistake this page exists to prevent.