Food Expiration Dates

They’re something we check virtually every single day, but do we understand what our food expiration dates actually mean? The interesting thing is, there’s no absolute rule on defining them, andno black and white on what’s good to eat and what’s not. But with food waste becoming a growing consumer concern, is it time we got to grips with “sell by” and “best by” dates a bit better?

In the UK alone, 2015 saw around ten million tonnes of food wasted, equating to around £20bn in total value. Perhaps if we knew the meaning behind how expiration dates are formulated, we could reduce those numbers significantly. Here’s a quick guide to how they work.

Sell by vs. best by vs use by

It’s fair to say that a lot of consumers are largely cautious with their food consumption, and that caution relies heavily on the expiration dates provided. Some consumers may go as far as to not eat food near or on the day or its given expiration, while others will happily risk going a few days beyond. Needles to say, the former group are throwing away perfectly edible food, but do they understand why?

It’s important to make a distinction between “sell by” and “use by” (or “best by”) dates, because there is one to be made.“Sell by” dates are in fact more to do with a shop’s stock rotation rather than an indication of food freshness, so shouldn’t be taken as a true expiration date. “Use by” and “best by” dates should be interpreted literally, as indicators of when the manufacturer deems the food will have gone past its peak freshness.

No expiration date provided actually indicates when a product has turned from safe to unsafe, which is important to know when simply considering whether food is still safely edible.

How do companies come up with dates?

Where larger manufacturing companies are concerned, the judgement around a certain product’s expiry can be based on a variety of tests:
  • Microbial challenge studies: Researchers take a pathogen of potential concern and add it to a specific product, before storing it in realistic conditions that replicate transportation, storage and in-store conditions. They will then monitor the product, carrying out various tests to determine when exactly it has become unsafe to eat, generating the “use by” date.
  • Mathematical modelling: Companies can combine the results of past challenge studies with the properties of their chosen product (ie. moisture content,expected storage temperature and acidity level) to perform a calculation which will give an estimated date of expiration.
  • Static test:The product is stored under typical conditions for an extended period of time, during which researchers will periodically test various features of safety and quality.
  • Rapid testing:The product is subjected to accelerated conditions, creating a quicker test process and answer. From the results, researchers can expand on the data and calculate an actual shelf life in normal conditions.
In all cases, the “use by” date stated on the product will be moved forward a few days by the manufacturer in order to give themselves a further cushion against their estimates. That means your typical expiration date will likely offer a good few days leeway where it’s still perfectly edible.

Smaller companies will typically list a date based on similar products from their competitors, or do their own testing.Retailers like RS Components provide a range of refractometers that can assess the freshness of a product.

It’s your call

When it comes down to it, there is no definitive answer on a products expiration because of so many changing circumstances being at play. The manufacturer’s research is fundamentally best guess work with a cushion inserted to protect both themselves and the consumer. Where food actually becomes unsafe to eat is not absolutely defined by the numbers you see on the package.

What this means is judging a food’s true expiration will depend largely on your common sense. Obvious signs such as change in appearance and smell, visible mould or an inflated sealed packet are typical signs of an issue, but consumers should also be aware of the state of the conditions they have stored their products in.

When it comes to trusting expiration dates, they’re certainly a good guideline to work by, but your own judgement shouldn’t be ignored when it comes to a final call on your food.