SOP: Detection of Foreign Bodies in Canned Products
GIFSQ — Global Institute for Food Safety & Quality
Principle
Foreign bodies are separated according to their nature: glass fragments are recovered by liquefying solid or pasty foods with dilute nitric acid, light materials are separated on a fine sieve with a water stream, and heavy inorganic matter is separated by washing and sedimentation.
Apparatus required
- Flask
- Fine sieve
- Large container (for the heavy inorganic material separation)
Reagents
a. Dilute nitric acid — for liquefying solid or pasty foods in the glass-fragment test.
b. Water, preferably hot — for the light-material separation.
Procedure — Glass fragments
Glass can get into the container when an electric bulb or glass pane shatters, a thermometer breaks, a glass container chips, or the like; in liquid and semi-liquid foods the pieces are easy to spot
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With a solid or pasty product, boil the whole can contents with dilute nitric acid until the mass liquefies
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The fragments sink to the bottom of the flask; recover them by careful washing, decantation, and a final filtration
Procedure — Light materials
Look through the sample for light materials — wood fragments, string, large insects — on a fine sieve, playing a gentle stream of water over it (hot water works best) to free bulky or pasty foods
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Small and microscopic foreign bodies of insect or animal origin are detected by the microanalytical methods given in the book’s Chapter 24
Procedure — Heavy inorganic material
Any solid matter that acid would destroy is separated by washing and/or sieving instead
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Material heavier than water is separated by placing it in a large container and flushing with a rapid flow of water
Precautions
- Boil solid or pasty foods with dilute nitric acid only until the mass becomes liquid.
- Use careful washing, decantation and final filtration so that no glass fragments are lost.
References
Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition.