Optimized Monier-Williams method for determination of sulfites in foods: collaborative study

Area of Science:

• Analytical Chemistry
• Food Science
• Regulatory Science

Background:

• Sulfite determination in food is crucial for regulatory compliance and consumer safety.
• The Monier-Williams method is a standard technique, but optimization is key for accuracy.
• Previous methods required validation for diverse food matrices.

Purpose of the Study:

• To collaboratively study and validate the optimized Monier-Williams method for sulfite determination in various food matrices.
• To assess the method's performance and reproducibility across multiple laboratories.
• To provide an alternative to the existing AOAC modified Monier-Williams method.

Main Methods:

• A collaborative study involving 21 industry and government laboratories.
• Use of the Food and Drug Administration (FDA)-optimized Monier-Williams method.
• Analysis of 3 food matrices (hominy, fruit juice, protein) at multiple sulfite levels (blank, half, regulatory, twice regulatory) as blind duplicates.

Main Results:

• Reproducibility (among-laboratories) coefficients of variation ranged from 15.5% to 26.6% for sulfite (as SO2 by weight) at the 10 ppm level.
• The method demonstrated consistent performance across different food types.
• Collaborators successfully demonstrated proficiency before participating in the main study.

Conclusions:

• The optimized Monier-Williams method is a reliable and reproducible technique for sulfite determination in foods.
• The method has been approved as interim official first action, replacing the previous AOAC method.
• This validated method supports accurate sulfite analysis in the food industry.