Spoilage of Canned Foods - Distortion of Cans


  • Canned goods are classified as spoiled when the food has undergone a deleterious change or when the condition of the container renders such change possible.
  • Spoilage may be due to variety of causes, and spoiled cans may usually show obvious of abnormalities such as distortion, blowing, concave ends or slightly constricted sides; or they may present a perfectly normal external appearance.
  • The various ditortions commonly encountered are:

Swell or blower

  • A can with it ends bulged by positive internal pressure due to gas generated by microbial or chemical activity is termed as swell or blower.


  • A flipper is a can of normal appearance in which one end flips out when the can is struck against a solid object but the end snaps back to the normal when very slight pressure is applied.


  • A springer is the term used to describe a can in which one end is bulged but can be forced back into normal position, where upon the opposite end bulges.


  • A leaker is a can containing a perforation from any cause whereby atmospheric air may enter the can or its contents escape.
  • May be detected by disappearance of vacuum from the sides and ends of the cans and the bubbles that appear from the can when held under water and squeezed.
  • Another test for leakage is to heat the can until the temperature is 38°C in the interior and allowing it to cool slowly. When if a leak is present, there will be no concavity of the sides or ends.
  • The commonest leaking is at the seams, and may sometimes be detected by the appearance of liquid or stain on the can surface.
  • Mould formation on the surface of canned meat is also indicative of leakage through the seams but cannot be detected until the can is opened.
  • The detection of leakers by striking the suspect tin with a mallet has little value in industrial practice.

Over filled can

  • An overfilled can is one in which the ends are convex due to overfilling.
  • Though an overfilled can, cannot properly be regarded as a spoiled can, it must be differentiated from a blower, and it emits a dull sound when struck, where as a blown tin emits a resonant sound.

Slack caps

  • The term slack cap is used in the trade to denote a can, which has a movement of one of the ends similar to a can in the early stages of blowing, and the great majority of can classed as slack caps are blown and should be treated as such.
  • Blower and slack caps should be condemned.
Last modified: Tuesday, 10 April 2012, 10:57 AM