Re: Are there ways to test foods for sulfur dioxide, if so how?

Hi Beth,

I will try and provide some information that might assist you with your 
project. As you already know sulfur dioxide and other sulfiting agents are 
permited as food additives. When one analyzes foods for these compounds we 
usually look for residual sulfite. The methods that are used in the 
industry require sophisticated analytical equipment (High Performance 
Liquid Chromatographs). There are test strips sold which can be used to 
estimate the sulifite content in liquids. You might be able to adapt them 
to solid food products by extracting the foods with water, filtering and 
using the strips to determine the sulifite concentration in the filtrate. 
You can purchase these test strips from Fisher Scientific 
(www.fishersci.com). They are called Quant* Test Strips and are found on 
page 1935 of the Fisfer catalog. The price is $38.53 for 100 test strips.
I hope this information proves to be of assistance, and good luck with your 
project.

Sincerely,

Al Bushway

Professor of Food Science

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Admin note:

Don Schaffner adds the following:

An FDA training manual on the web:

http://www.fda.gov/ora/science_ref/lpm/lpchtr13.html


lists two sulfur dioxide test methods.  Here is an excerpt from the online
manual.

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13.3.2.2 Sulfites


A. Introduction

Sulfur dioxide and sodium and potassium bisulfites and metabisulfites are
used in foods as antioxidants and bleaching agents. Sulfites are commonly
used as preservatives in dried fruits and as bleaching agents in the
processing of maraschino cherries.

This exercise requires the trainee to determine the amount of sulfite,
calculated as sulfur dioxide, present in a preserved food.

B. Assignment

The trainer will provide a sample of dried fruit preserved with sulfides.
Determine the amount of sulfite present. as sulfur dioxide. using the
Monier-Williams Procedure (with Modifications), also referred to as the
Optimized Monier-Williams Procedure published in the Federal Register,
Vol. 51, No. 131, July 9, 1986, pp. 25017-20. Also perform the AOAC
gravimetric determination. 962.16C.

C. References

1. Federal Register, Vol. 51, No. 131, July 9, 1986, pp. 25012-26.

2. AOAC Official Methods of Analysis." 15th ed., 1990: 962.16C.

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A good librarian should be able to get copies of both documents via
interlibrary loan.