SOP: Determination of pH of Normal and Spoiled Cans

GIFSQ — Global Institute for Food Safety & Quality

Principle

Spoilage organisms change the acidity of the product — flat-sour spoilage, for instance, markedly lowers the pH. Comparing the pH of normal and spoiled cans from the same lot with a glass-electrode pH meter therefore detects spoilage shifts, and even small variations can be significant.

Apparatus required

• pH meter with glass electrode

Procedure

Take normal and spoiled cans from the same lot

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Determine the pH of each using the pH meter with glass electrode

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Compare the pH values of the spoiled cans against the normal cans

Interpretation

• pH determination is of particular importance when flat-sour is suspected.
• Variations in pH, even as small as 0.15 to 0.2, may often be significant.

Precautions

• Compare only cans from the same lot — product-to-product pH differences are natural.
• Do not taste spoiled foods.

References

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