Optimized Monier-Williams Method for Determination of Sulfites in Foods: Collaborative Study

Abstract

A collaborative study was conducted of the Food and Drug Administration (FDA)-optimized Monier-Williams method for determining sulfites in foods. Twenty-one industry and government laboratories participated in the study, which was jointly sponsored by the National Food Processors Association and FDA. Familiarization samples were shipped to each collaborator. Collaborators were permitted to proceed to the main study only after they demonstrated ability to perform the method to ensure that the study tested the performance of the method itself and not that of the individual laboratories. The study design involved 3 food matrixes (hominy, fruit juice, and protein [seafood]). Each matrix was prepared at 3 sulfite levels—the regulatory level, half the regulatory level, twice the regulatory level— and as a blank. All test samples were analyzed as blind duplicates, which gave each collaborator a total of 24 test portions. Collaborative recoveries gave a reproducibility (among-laboratories) coefficient of variation that ranged from 15.5 to 26.6% for sulfite determined as S02 by weight in the 3 foods at the 10 ppm level. The optimized Monier-Williams method has been approved interim official first action to replace the AOAC modified Monier-Williams method, 20.123-20.125.

Control of Listeria monocytogenes in Vacuum‐Packaged Pre‐Peeled Potatoes

“…Potatoes received one of 4 different treatments: (1) immersion in 1.2% (w/ v) sodium bisulfite for 2 min, (2) immersion in a 2% (w/v) solution of a commercial browning inhibitor (CBI) consisting of citric acid, ascorbic acid, sodium acid pyrophosphate and L-cysteine HCl for 5 min, (3) immersion in a 2% solution of the CBI for 5 min, followed by a brief rinse with tap water (30 mL rinse/kg potatoes), or (4) untreated control. Residual sulfite levels were determined in uninoculated control samples by the Optimized Monier-Williams Method (Hillary et al, 1989).…”

Liquid chromatographic determination of free and total sulphites in fresh sausages

“…We wished to check whether a pH of 8.9 would be sufficient to produce dissociation of the reversibly combined forms. As a reference product HMS was chosen; this is the addition compound formed between sodium sulphite and formaldehyde and is also considered to be one of the most stable combined forms (Lawrence and Chadha 1988;Hillery et al 1989). HMS had already been used as a standard for the quantification of total sulphite and in recovery assays (Lawrence and Chadha 1988).…”

“…Sulphite was added in the form of HMS to avoid interaction between the free sulphite and certain components present in the samples which, in many cases, prevents correct evaluation of the recovery in the method employed (Cooper et al 1986;Holak and Specchio 1989). Furthermore, this compound is structurally similar to some combined forms of sulphite in foods (Hillery et al 1989) making it more appropriate for evaluating the extraction of the combined forms of sulphite than addition of inorganic salts of sulphite.…”

Studies of a urinary biomarker of dietary inorganic sulphur in subjects on diets containing 1–38 mmol sulphur/day and of the half-life of ingested 34SO42−

“…The chemistry of sulphur is such that SO 3 À and SO 2 are readily oxidized to SO 4 2À during food processing and storage (Wedzicha, 1992). However the AOAC method for the determination and regulation of sulphites in foods is an optimized Monier-Williams method (Hillery et al, 1989), which only measures SO 3 À and SO 2 . Therefore it is likely that foods will contain much more total IS in the form of SO 4…”