Best-before versus use-by

Why does a date printed to promise quality make people bin food that is perfectly safe?

Two dates sit on supermarket packaging, printed in the same font, in the same corner, in the same small type. One says best before. The other says use by. In European and UK law these mean genuinely different things: use by is a safety instruction, and best before is a quality promise about texture, flavour and appearance. Food past its best-before date is legally saleable in the UK and, in the ordinary case, entirely safe to eat.

Yet millions of tonnes of edible food are discarded each year on the strength of a date that was never about safety. So the question is not really "what do the labels mean?" — that is settled and documented. It is the more interesting one: how does a label mean one thing and get read as another so consistently that the reading, not the meaning, is what governs behaviour?

Start with what each date is actually derived from, because the two come from different laboratories in a real sense.

A use-by date comes from a microbiological shelf-life study. A manufacturer challenges the product — inoculates it, or stores it under defined conditions and monitors it — and asks when a pathogen such as Listeria monocytogenes could plausibly reach a hazardous level under normal domestic storage. That is a safety threshold, it applies to highly perishable foods, and eating past it carries a real, if probabilistic, risk. In the UK it is an offence to sell food past its use-by date.

A best-before date comes from a sensory and quality study. When do the biscuits go soft? When does the oil oxidise enough to taste? When does the colour of the tinned tomatoes shift? Nothing hazardous happens at that boundary. Dried pasta, tinned pulses, sugar, honey, rice: these carry best-before dates because the law requires a date of minimum durability, not because anything begins to go wrong on the morning after.

Now ask what a shopper has, standing at the fridge. Two words, in a small font, on a substrate that is often shiny or curved. No indication of which was derived from a pathogen model and which from a taste panel. And behind that, a general prior that dates on food are warnings — because that is what an expiry date means on medicine, on a driving licence, on a parking ticket. The word expiry is not even on the pack, but it is the concept people arrive carrying.

Follow that through to the decision itself. The shopper is making a judgement under uncertainty with a badly asymmetric payoff as they perceive it. Downside of eating something bad: illness, and a vivid, memorable, personally blameable one. Downside of binning something fine: a couple of pounds and a vague sense of waste, diffused and invisible. Which error would you rather make at eight in the evening with a toddler waiting? The label does not need to say "danger" for the cautious reading to dominate; it only needs to be ambiguous, because the perceived costs do the rest.

And here is the step worth pausing on. If both dates get read as safety deadlines, then adding a best-before date to a stable product does not add information — it removes it, by overwriting the shopper's own senses with a printed number. What could you actually tell from a carrot? Rather a lot: firmness, smell, appearance. What can you tell from a date printed weeks earlier by someone who never saw your fridge? Less than you can tell yourself. The label displaces a reliable local judgement with an unreliable remote one.

That reasoning is why several major UK retailers — Waitrose, Marks and Spencer, Sainsbury's, Tesco and Co-op among them — removed best-before dates from large parts of their fresh fruit and vegetable ranges through 2022, explicitly to reduce household waste. It is a rare case of the intervention following the diagnosis exactly: the fix was not clearer wording but deleting the number where it carried no safety content at all.

Three clarifications keep this from tipping into the opposite error.

First, the distinction is real and use-by dates deserve respect. This is not an argument that all dates are theatre. For chilled ready meals, smoked fish, cooked meats and unpasteurised dairy, the use-by date is tracking a genuine growth curve, and Listeria in particular can multiply at refrigeration temperature — which is exactly the case where your senses fail you, because the food does not look or smell wrong. The senses that outperform a best-before date underperform a use-by date.

Second, the trouble is not that people are careless. It is that a good decision procedure needs a reliable signal, and two visually identical labels carrying different logical force do not provide one. Framing this as consumer ignorance points the fix at the reader rather than at the design, which is where it belongs.

Third, freezing quietly dissolves much of the problem, because it moves the food out of the regime the dates were computed in. UK guidance now says food can be frozen any time up to the end of the use-by date rather than only on the day of purchase — a small change of rule that converts a deadline into an option.

• Whether time-temperature indicator labels, which respond to actual storage, could replace fixed dates.
• Why Listeria growth at fridge temperature makes the use-by date genuinely non-negotiable.
• How date-label conventions differ in the United States, where most dates are not federally defined at all.

Every term the collection defines is gathered in the glossary.