Flat Souring


  • The flat souring in canned goods is manifested by the presence of a sour odour of foodstuffs, but without the can becoming blown.
  • Canned foods susceptible to this deleterious change are those containing sugar or starches, and meat products such as sausages or paste containing cereals. 
    • True flat sours are commonly caused by the growth of thermophilic organisms (B.coagulans, B.stearothermophilus, B.circulans), which attack carbohydrates with production of acid but not gas.
    • The exceptional heat resistance of such organisms makes them to survive the normal processing given to the canned foods.
    • Sourness in canned foods may also arise due to leaking cans or it may have developed in the food before processing.
    • The latter forms of spoilage is the most liable to occur in cold-filled pack in warm weather, and its incidence is greatly increased by allowing the product to be stored in open for even short period prior to processing.
    • In corned beef, the presence of souring without gas production may be due to under-processing or leaking seams, but the development of pre-processing storage is also likely to be the cause.
  • Flat sours of canned foods due to thermophilic spore forming organisms can not be detected until the can is opened and its content examined, but is unlikely to occur in temperate climates but its  occurrence is common in tropical and sub-tropical countries or when cans imported to temperate climate from hot climates.
Last modified: Tuesday, 10 April 2012, 11:01 AM