MadSci Network: Biochemistry

Re: sodium metabisulfate for a browning inhibitor for apples

Date: Thu Mar 30 07:49:43 2000
Posted By: Alfred Bushway, Professor of Food Science
Area of science: Biochemistry
ID: 953853745.Bc

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.


Al Bushway
Professor of Food Science

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