Chemical Spoilage - Hydrogen Swell


  • The most impotant problems encountered in the canning industry owing to spoilage on account of  chemical changes are Hydrogen Swelling, Purple Staining and Rust or Damage.

Hydrogen Swell

  • Hydrogen swell happens independent of microbial spoilage, and is associated with the formation of hydrigen gas in the can following internal corrosion.
  • Imperfection or scratches on the inner coating may expose small areas of steel and when the contents are acid, an electric couple may result, the reaction producing hydrogen gas.
  • Electrolytic action is accelerated by the presence of atmospheric oxygen and by the colouring matter – anthocyanine of the red fruits.
  • Lacquering of can also increases the rate at which hydrogen swells are formed.
  • For cracks inner lining of the lacquer serves to concentrate electrolytic action on the areas of iron exposed by the cracks.
  • Can affected with hydrogen swell may show varying degrees of bulging from flipping to blowing and if the tin being punctured, there is emission of hydrogen gas, which is odorless and burns on the application of a flame
  • This condition is chiefly associated with food containing organic acids particularly fruits such as plums, cherries, raspberries, etc.
  • The range of acidity most favorable to the production of hydrogen swells lies between pH 3.5 and 4.5.
  • This condition is unknown in canned meat foods, but it is sometimes seen in sardines.
  • Judgement
    • Though the content of the can in hydrogen swell may be quite harmless, the routine methods employed in the examination of canned goods render it impossible to distinguish between the tins which are blown due to hydrogen swell and those which are blown as a result of deleterious changes due to bacteria or yeasts.
    • So, all blown tins, leakers, springers and flat-sours together with tins whose contents show evidence of mould must be regarded as unfit for food, hence, should be condemned.
Last modified: Monday, 18 April 2011, 2:04 PM