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SOP: Detection of Mineral Acids in Vinegar

GIFSQ — Global Institute for Food Safety & Quality

Principle

Free mineral acid in vinegar changes the colour of methyl violet indicator to blue or green, which reveals its presence.

Reagents

a. Methyl violet solution: mix 1 part of methyl violet 2B in 10,000 parts of water.

b. Water.

Procedure

To 5 ml of the vinegar, add 5 to 10 ml of water

↓

Add 4 to 5 drops of the methyl violet solution

↓

A blue or green colour indicates the presence of free mineral acid

Precautions

  • A blue or green colour is the positive result; no colour change means no free mineral acid.

References

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