Page 127 - Analytical method for food addtives

E220–8: Sulphites 77

infrared spectrometry’, Perez-Ponce A, Garrigues S, de la Guardia M. Quimica Analitica
(2000) 19(3), 151–158.
22 ‘The determination of total SO in grape juice. A comparison among five methods’,
2
Ferrarini R, Celotti E, Versari A, Galassi S. Food Additives and Contaminants (2000)
17(12), 973–977.
23 Validation of Enforcement Methods Service (VEMS) Method Ref 0158: Gravimetric
Method for Sulfur Dioxide in Meat Products.
24 Validation of Enforcement Methods Service (VEMS) Method Ref 0360: Titration
Method for Sulfur Dioxide in Foods, General.
25 Validation of Enforcement Methods Service (VEMS) Method Ref 0308: Titration
Method for Sulfur Dioxide in Foods, General.
26 Validation of Enforcement Methods Service (VEMS) Method Ref 0246: Titration
Method for Sulfur Dioxide in Foods, General.
27 ‘Dietary intake exposure to sulfites in Italy – analytical determination of sulfite-
containing foods and their combination into standard meals for adults and children’,
Leclerq C, Molinaro M G, Piccinelli R, Baldini M, Arcella D, Stacchini P. Food
Additives and Contaminants (2000) 17, 979–989.

8.5 Appendix: method procedure summaries

Analysis of foodstuffs with sulphite content ≥≥ ≥≥ ≥10 mg/kg using optimised
Monier–Williams method 2

Scope
Distillation method for determination of sulphite content, expressed as sulphur
dioxide. The method is applicable in the presence of other volatile sulphur
compounds. It is not applicable to cabbage, dried garlic, dried onions, ginger, leeks
and soy proteins.

Principle
Free sulphite plus reproducible portion of bound sulphites (such as carbonyl
addition products) in foods are measured. The test portion is heated with a
refluxing solution of hydrochloric acid to convert sulphite to sulphur dioxide. A
stream of nitrogen is introduced below the surface of the refluxing solution to
sweep sulphur dioxide through water-cooled condenser and via a bubbler attached
to the condenser, into the hydrogen peroxide solution, where sulphur dioxide is
oxidised to sulphuric acid. The generated sulphuric acid is titrated with standard-
ised sodium hydroxide solution. The sulphite content is directly related to the
generated sulphuric acid (see ).
3,4
Procedure
Sample preparation and analysis should be carried out as quickly as possible to
avoid loss of labile forms of sulphite.
(Note: to become familiar and proficient with the method before routine use, it
is recommended that food test portions containing known amounts of sulphite are
analysed. The analysis should be performed in a manner that precludes any loss of