What causes a lid that sealed to bulge or to come unsealed during storage?
Both bulging and loss of seal are signs of spoilage. If either of these occur, discard the food. It could be dangerous.
Spoilage organisms must be growing in the food and
producing gas. The build up of pressure inside the jar
results in bulging or loss of seal. Growth of spoilage
organisms can be attributed to under-processing (product
was processed by wrong method or too short a time) or to
a hairline crack in the jar which permitted entry of
organisms during storage.
Never taste home canned food when the lid has bulged
or come unsealed.
Barbara Willenberg, Nutritional
Sciences, University of Missouri-Columbia
Last update: Tuesday, May 05, 2009