Erythorbic Acid

Is erythorbic acid allowed for use in organic processing?

By Andria Schulze

Erythorbic acid is a stereoisomer of ascorbic acid (Vitamin C). While ascorbic acid is allowed as a synthetic ingredient in or on processed organic products at §205.605 in the NOP regulations, the issue of stereoisomers is not addressed in the rule. A stereoisomer is a molecule that has the same formula and sequence of bonded atoms as another, but differs in its three-dimensional orientation. For example, if your hands were molecules and your palm and digits atoms, your left hand would be a stereoisomer of your right. 

Both ascorbic acid and erythorbic acid are commonly used as anti-oxidant preservatives in a wide variety of foods.  The use of erythorbic acid as a preservative in foods intended to be eaten raw has increased since the US FDA banned the use of sulfites for this purpose.

Since the NOSB did not specifically discuss erythorbic acid during its Technical Advisory Panel (TAP) reviews for Ascorbic acid, the real question is whether or not erythorbic acid is chemically the same as ascorbic acid. The materials have different CAS registry numbers, and this is an indication that they are distinct chemicals. One does not fall under the identity of the other, according to the American Chemical Society.

While studies show that natural and synthetic ascorbic acid behave similarly in biologic systems, stereoisomers of ascorbic acid show a decreased anti-ascorbutic activity in comparison. This is a clear indication that the materials are functionally different in metabolic systems, at least in degree.

OMRI consequently regards the two materials as chemically and functionally distinct, and does not consider erythorbic acid to be included in the allowance of ascorbic acid for organic processing. Those wishing to use the ingredient in organic processing would be encouraged to petition the NOP to have erythorbic acid specifically addressed.

Revised and updated in January 2018 by OMRI Technical Director Johanna Mirenda. This article was originally published in the Spring 2011 edition of the OMRI Materials Review newsletter.