The revelation that employees of Tesco and Sainsbury's have been caught by a BBC undercover team extending the "use-by", and "sell-by" dates on food provides just another reason for adopting a healthy scepticism towards such apparently informative labels.

For starters, don't put too much faith in "sell-by" and "display until" dates. These are just stock control devices for retailers. Foods past these dates could still be fine to eat. Similarly, the term "best before" is not about safety, but merely represents the manufacturer's or retailer's estimate of how long the product will remain in good condition. Biscuits, say, may be better eaten within the "best before" period but after that they aren't going to kill you.

"Use-by" dates are the ones to note. These are found mainly on chilled perishables such as meat, fish, poultry, eggs and sandwiches, which can rapidly deteriorate and become dangerous to eat. But even these are pretty random. A standard intensively reared broiler chicken, for example, will very likely be contaminated with nasty bugs such as campylobacter and salmonella when still within its date. The only way to destroy these pathogens is thorough cooking. On the other hand, while it is unwise to eat eggs beyond their use-by date if serving them lightly cooked, it is fine to use them up by baking them thoroughly in a cake.

Rather than relying on date labels, it's a good idea to understand which foods pose the greatest food-poisoning risk: poultry, eggs, undercooked burgers and sausages, ready meals, soft cheeses and cooked, processed meats. Exercise extreme caution with these, and you can afford to be a bit more laid back about products that are baked (old Christmas cake), or preserved by dint of being either very salty, very acidic, alcoholic or very sweet (parmesan, vinegar, wine, golden syrup).