SOP: Gas Analysis of Headspace for Detection of Hydrogen Swells

GIFSQ — Global Institute for Food Safety & Quality

Principle

A swollen can with a low microbial count may not be a microbial swell at all: hydrogen gas produced by corrosion of the can’s internal surface can swell it. Analysing the headspace gas separates the two — hydrogen burns, while the microbial gases of spoilage do not behave the same way.

Apparatus required

• Flame (for the combustible-gas test)
• Orsat-type gas analyser (for differential analysis)

Procedure

Take the swollen can in which the microbial count is low

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Analyse the headspace gas: demonstrate the combustible nature of the gas by making a small puncture in the can while holding it adjacent to a flame, or carry out a differential analysis using an Orsat-type gas analyser

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Examine the internal surface of the can — in hydrogen swells it would show signs of heavy corrosion

Interpretation

• Gas that burns on puncture near a flame, with a heavily corroded internal can surface, indicates a hydrogen swell rather than microbial spoilage.

Precautions

• Puncture the can carefully and keep it away from the body — pressure and flame are both hazards.
• Open swollen cans only by the swollen-can procedure.

References

Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition.