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Acidified Sodium Chlorite

How can acidified sodium chlorite be used in organic food processing?

By Sam Schaefer-Joel

Acidified sodium chlorite (ASC) was added to the National List at §205.605(b) on March 15th, 2012. It is allowed to be used for both indirect food contact surface sanitizing and secondary direct antimicrobial food treatment. Indirect food additives and secondary direct food additives are regulated differently by the FDA. Indirect food contact use is fairly intuitive; for example, treatment of food processing equipment followed by adequate draining before food contact. Secondary direct antimicrobial food treatment is a little more complex. Secondary direct additives are applied directly to food, but they only have a technical effect during food processing and handling and do not persist and continue to have a technical effect in the finished food product. For example, when a chicken carcass is dipped in an ASC solution, the ASC acts to kill microbes on the surface of the chicken. However, the ASC breaks down quickly and does not continue to provide a long term antimicrobial effect for the final poultry product.

The FDA specifically addresses the allowed food contact uses of ASC at §173.325 of the CFR. It may be used in meat, fish, and poultry processing, as well as on both raw and processed agricultural commodities, fruits and vegetables. Some uses have specific restrictions regarding rinses and maximum rates of use. Be sure to follow product label instructions for the appropriate type of use and always check with your certifier before incorporating any new material into your organic food processing/handling operation.

The OMRI category Acidified Sodium Chlorite was created soon after the material was added to the National List. This is an unusual category for OMRI; despite the name, products in this category are not reviewed by OMRI in their acidified state. ASC products must be acidified at the time of use in order to be effective. This is due to the reaction that occurs when acids and sodium chlorite are combined. When used in organic production, ASC may only be acidified by citric acid. The addition of the acid to sodium chlorite creates the unstable species, chlorous acid. Chlorous acid is a very strong oxidizing agent and breaks down rapidly to form other oxy-chlorine species such as chlorine dioxide, chlorate, and chlorite. Chlorine dioxide itself is a strong oxidizing agent that breaks down into chlorite and chloride ions.

The antimicrobial effect of an ASC solution is mainly due to the presence of chlorous acid and chlorine dioxide. These compounds act by disrupting microbial membranes and oxidizing cellular components. ASC solutions are commonly used to kill bacteria, viruses, fungi and algae.

Because OMRI is not able to review the acid that will be utilized at the point of use in order to activate OMRI Listed® products in the category: Acidified Sodium Chlorite, certifiers should take extra care to verify that only citric acid is being used to activate the sodium chlorite solution.

Revised and updated in April 2017 by OMRI Technical Director Johanna Mirenda. This article was originally published in the Summer 2013 edition of the OMRI Materials Review newsletter.