Foodstuff information - Tinned foods

Discovering a foreign object in food is a very unpleasant experience. However, not all pose a serious health risk. Here are some common food complaints together with a short explanation and suggestions for the best course of action.


Occasionally, small grubs may be discovered in canned vegetables especially sweetcorn and tomatoes. The grubs are the larvae of a moth that live inside the sweetcorn kernel or tomato and are impossible to see before they are processed. Although it isn’t pleasant to find a grub in your food, they are killed and sterilised by the canning process. As the use of pesticides decreases, these types of problem will increase.

  • Advised Action: Contact the manufacturer
  • Risk: No public health risk

Wasps and Fruit Flies

These are naturally associated with fruit and so are often found in tins of fruit. They do not carry disease.

  • Advised Action: Action:  Contact the manufacturer
  • Risk: No public health risk


Some naturally occurring elements in fish may develop into hard crystals during the canning process. These crystals may be mistaken for glass fragments and are called struvite. They are not harmful and will be broken down by stomach acid if swallowed. Struvite is especially common in tinned salmon and will dissolve if placed in vinegar and gently heated for up to 15-20 minutes (they may not dissolve completely in this time but will reduce in size). Glass will not dissolve.

  • Advised Action: Action:  Heat gently in vinegar for 15-20 minutes, if struvite contact the manufacturer, if glass contact the Food Safety Team.
  • Risk: No public health risk if struvite, is a public health risk if glass


Dented, damaged or incorrectly processed tins may allow mould growth to occur. This could indicate an error in production or storage.

  • Advised Action:  Contact Food Safety Team (Regulatory Team - Environmental Health)
  • Risk: Possible public health risk


Small grubs are often found in canned vegetables, particularly tomatoes and sweetcorn. Their colour is often cream to greenish brown with long dark and pale bands, but this is variable. They can be up to 4 cm in length. People think they may be maggots or caterpillars. These are moth larvae that live inside the food, and are difficult to see during growing and processing. The larvae are killed and sterilised by the canning process so they are not a health risk. Every effort is made to control these pests while crops are growing. But you may find these larvae in food as the use of pesticides in food crops has decreased and there is an increase in the use of organic produce, where crops are not sprayed with any chemicals. 

  • Advised Action: Although unpleasant to find a grub in the food. You should contact the manufacturer
  • Risk:  No public health risk



Last Updated on Wednesday, May 8, 2024