How can you tell that food has spoiled, and what do date labels mean?
The signs of food spoilage (changes in smell, taste, texture, colour and the appearance of mould), the difference between use-by and best-before dates, and the meaning of high-risk foods.
A focused answer on the signs of food spoilage for OCR GCSE Food Preparation and Nutrition (J309), covering the changes that show food has spoiled, the difference between use-by and best-before dates, high-risk foods, and how to store food to slow spoilage.
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What this dot point is asking
OCR wants you to recognise the signs that food has spoiled, understand the difference between use-by and best-before dates, and know what high-risk foods are. The key safety message is that some dangerous bacteria leave no visible sign, so dates and storage matter as much as the senses.
The signs of spoilage
These changes are caused by microorganisms (bacteria, yeasts, moulds) multiplying and by the food's own enzymes continuing to act after harvest or slaughter. A blown can or a bulging vacuum pack is a serious warning that gas-producing bacteria have grown, and the food must not be eaten.
The crucial safety point
Use-by and best-before dates
- Use-by date - about safety. Found on high-risk, perishable foods such as raw and cooked meat, fish, dairy products, ready meals and prepared salads. The food should not be eaten after the use-by date, because harmful bacteria may have grown to dangerous levels even if it looks fine. You can usually freeze food up to the use-by date to extend its life.
- Best-before date - about quality, not safety. Found on longer-life foods such as tinned, dried, frozen and packaged foods. After the best-before date the food may have lost some flavour, texture or colour but is usually still safe to eat.
High-risk foods
Storing food correctly (in the fridge below degrees C, covered, with raw and cooked foods kept apart) slows spoilage and keeps high-risk foods safe up to their use-by date.
Try this
Q1. Which date label is about safety rather than quality? [1 mark]
- Cue. The use-by date.
Q2. Give two signs that food has spoiled. [2 marks]
- Cue. Any two of: off smell, off taste, slimy or changed texture, change in colour, mould, blown packaging.
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 20194 marksExplain the difference between a use-by date and a best-before date, and state which one is about safety.Show worked answer →
A 4-mark structured question.
A use-by date is about safety. It is found on high-risk, perishable foods such as raw meat, fish, dairy and cooked meals. The food should not be eaten after the use-by date because harmful bacteria may have grown to dangerous levels, even if it looks and smells fine.
A best-before date is about quality, not safety. It is found on longer-life foods such as tinned, dried and frozen foods. After the best-before date the food may have lost some flavour, texture or colour, but it is usually still safe to eat.
Markers reward use-by being the safety date on high-risk foods (do not eat after it) and best-before being a quality date on longer-life foods (still usually safe after).
OCR 20214 marksDescribe four signs that a food has spoiled and should not be eaten.Show worked answer →
A 4-mark question, one mark per clear sign.
Any four of: an unpleasant or sour smell; an off or sour taste; a change in texture (slimy meat or fish, soft or mushy fruit and vegetables); a change in colour (browning, greying or discolouration); the appearance of mould (fuzzy patches); bubbling or a swollen, blown packaging or can (gas from microorganisms); curdling or separation in dairy.
Markers reward four distinct, sensible signs of spoilage. A good answer notes that some harmful bacteria do not change the smell or look of food, so date labels and safe storage still matter.
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