|MadSci Network: Biochemistry|
I will attempt to provide answers to the questions you have posed. There are several methods for measuring the sulfite levles in foods, which include titration, distillation followed by titration, gas chromatography, and colorimetric analysis. Sulfite can also be specifically oxidized to sulfate by the commercially available enzyme sulfite oxidase. Ascorbic acid can interfere with the assay but can be removed by using ascobic acid oxidase. As you can see these are not simple methods. There are test strips avialable from any of the major scienctific supply companies (i.e. Fisher Scientific) for measuring sulfite. I do not know if they will work for your specific application. If you are not aware of the potential food safety problems with sulfites, you need to know that some asthmatics have severe allergic reactions when exposed to low concentrations of sulfites. There are also labeling requirements if sulfites are used on/in food products. Citric and ascorbic acid or combinations of the two are used as anti-browning agents. For home use, lemon juice which contains citric acid is used. Calcium chloride is not a anti-browing agent, but is used to maintain the texture of fruits and vegetables (inhibits softening). I hope this information will be useful. Sincerely, Al Bushway Professor of Food Science
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