National Organic Standards Board

Handling Subcommittee Proposal

Review of the Ion Exchange Filtration Process and Materials Used

February 17, 2021

Background: 

In an August 27, 2019 memo, the National Organic Program (NOP) requested the NOSB provide a 

recommendation related to the process of ion exchange filtration in the handling of organic products. It 

has become clear that there is inconsistency between certifiers in how they approve or disapprove this 

type of process. Some certifiers require only the solutions used to recharge the ion exchange 

membranes be on the National List at § 205.605. Others require that all materials, including ion 

exchange membranes and resins be on the National List.

The National Organic Program provided clarification to certifying agents in an email sent on May 7, 

2019, that nonagricultural substances used in the ion-exchange process must be present on the National 

List. This would include, but is not limited to, resins, membranes, and recharge materials. Originally, the 

NOP asked all operations to come into compliance with the statement above by May 1, 2020. However, 

in response to requests for clarification of NOP’s rationale, as well as requests to extend the timeline for 

implementation, the NOP delayed the implementation date in order to gather more information and 

requested that NOSB review the issue.

The NOP has determined, and some Materials Review Organizations have agreed, that the ion exchange 

process is a chemical one and does affect the food in a way that chemically changes it. This process is 

different from physical filtration. In the ion exchange process, the liquid used in the process exchanges 

molecules with those being held on the surface of the resin. The FDA considers ion-exchange 

membranes and resins to be secondary direct food additives, since there is an effect on the liquid used 

in this process.

Manufacturers and certifiers who wish to continue allowance of the ion exchange process, disagree with 

some of the findings of the NOP on this complex issue. The different opinions about the need for resins, 

recharge materials, and membranes to be present on the National List, as well as how they interact with 

each other and the liquid run through the process, is complicated and the NOP therefore asked the 

NOSB to assess this issue.

A simplified summary of ion exchange, provided in the past from the Organic Materials Review Institute 

(OMRI), is as follows:

Ion exchange is based on the principle that a solid mass with immobilized charges can attract 

the mobile ions of the opposite charge in a fluid media. In practice, this involves a column that is 

like a large pipe packed with an exchanger, which may be in the form of beads, crystals, gels, or 

granules. The fluid can pass through, but the ions in solution will be pulled out and held to the 

exchanger. The process chemically changes the resulting fluid.

Techniques used to produce various sweeteners offer a good example of how the process 

works. Minerals, salts, proteins, and color bodies occur naturally in grape juice, cane juice, beet 

juice, and corn syrup. The refinement process seeks to remove these "impurities". They are also 

naturally present or—in the case of color bodies—are formed between naturally present 

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components during heating. These can be removed by a number of techniques. Some are 

physical, some are chemical, and some use both. However, the use of synthetic cross-linked 

polymeric resins—such as styrene-divinylbenzene (S-DVB)—to remove certain constituents of 

liquids based on their chemical properties is a chemical process. The liquified sweetener stream 

chemically reacts with the ions present on the ion exchange resin to purify and concentrate the 

desired sugar (Cantor and Spitz, 1956). 

Other processing aids that are considered secondary food additives required petitions in order 

to be considered. In addition to the filtering / clarifying / fining agents mentioned above, these 

also included the boiler water additives, antifoaming agents, and certain enzymes. Other 

additives that are considered ‘de minimis’ in conventional processing—such as disinfectants and 

atmospheric gases—also required petitions, reviews, and recommendations to be added to the 

National List. Ion exchange resins are known to leak from columns and thus become incidental 

additives in the food. 

Subcommittee Review: 

The question before the Handling Subcommittee is whether only the recharge materials for the resins 

must be on the National List or whether both the resins and recharge materials must be reviewed and 

added to the List.

The 2020 technical review (TR) provides a thorough review of ion exchange filtration and should be 

referred to for details on this process. It is clear that there is widespread use of ion exchange filtration 

in organic processing, whether it be for removal of off-tastes, heavy metals, or clarification of the final 

product, among others. Alternatives to ion exchange filtration are not generally available. 

As noted in the 2020 TR, ion exchange filtration differs from physical filtration processes in that there is 

an actual chemical change in the ensuing product – ions (either cations or anions depending on the resin 

and desired outcome) that were present on the resin have been substituted in the final product while 

ions that were initially found in the product are left attached to the resin. This is not just a physical 

removal of material or a reaction whereby another material is used to help process the initial substance 

and then removed after that process. The 2020 TR cites various research articles and states:

 

...ion exchange filtration requires the replacement of bound ions (ions initially present in the 

filtration material) by others with the same charge and requires electroneutrality... 

...ion exchange filtration is based on the principle that if an ion is removed from the treated 

substance by the filtration material, it is replaced by an ion of the same charge that began in the 

filtration material (e.g., removal of positive ion from treated substance is replaced by a different 

positive ion from the filtration material). The ion exchange process is a result of electrostatic 

attractions between the ion of interest (ion to be removed from the treated substance) and the 

charged functional groups incorporated into the filtration material.

The final product, by passing through the ion exchange filter, does have a different ionic makeup than 

the initial product. In the case of removing “hardness” from water, the substitution of sodium for the 

original calcium in the water does not change that it is still water, per se, but it can change how that 

interacts with other materials. Thus, it seems difficult to argue that ion exchange filtration does not 

cause a chemical change in the final product, even though the chemical change may be beneficial. 

There is a different ionic makeup in the final product as compared to the initial product and the final 

product may behave slightly differently than the initial product.

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Next, there is the question of whether the resins themselves contribute to a change in the final organic 

product or whether, as food contact substances, they are simply a structure that holds the ions to be 

exchanged. The 2020 TR states that there are studies that demonstrate that the resins do degrade over 

time, however that degradation is generally in terms of their loss of resin activity or efficiency or 

capacity. In other words, the resins are simply not as good at holding ions to be exchanged and thus 

need to be recharged sooner than they would when they were new. In some cases, this loss of efficacy 

may be because of a loss of functional groups that were originally present, however the citations 

referenced in the TR note that this loss seems to primarily occur during the recharge process. Thus, the 

loss of those functional groups would not be into an organic product, but rather into the recharge 

material. The 2020 TR further states that there were no published studies found on the human health 

effects of the degradation of the resins. Based on the findings of the TR and no public comments that 

provided scientific evidence that the resins degrade and cause changes in the final product it would 

seem that the resins act in the capacity of food contact substances and not primarily as direct food 

additives. However, these same resins can be included under secondary food additives.

There is a question of whether the ion exchange membranes and resins are secondary food additives or 

food contact substances. If they are food contact substances, then, based on past NOP guidance, they 

may be used unless explicitly prohibited. If they are secondary food additives, then they must appear on 

the National List. The NOSB received many public comments on both its Spring 2020 discussion 

document and Fall 2020 proposal with a number of viewpoints, however the comments from the 

Organic Trade Association provided the most details of FDA rule history on this topic:

In a policy statement issued on December 12, 2002, after consultation with FDA, NOP clarified 

which substances are subject to review and recommendation by NOSB for inclusion on the 

National List. According to the policy, substances that are listed in 21 CFR Part 173 as secondary 

direct food additives are subject to review, unless the substances are classified by the FDA as a 

food contact substance. In 2002, FDA clarified that ion exchange resins were food contact 

substances, therefore ion exchange resins under the 2002 policy were not subject to the

National List process. The 2002 food contact substance policy was archived when the NOP

Handbook was created; however, it has never been formally rescinded and remains in use by 

some certifiers. 

FDA references are as follows:

• Ion exchange resins and membranes are listed in 21 CFR Part 173 as secondary direct food

additives, which are substances that have a technical effect in food during processing but

not in the finished food.

• According to FDA guidance, some secondary direct food additives also meet the definition of 

a food contact substance, which is any substance that is intended for use as a component of 

materials used in manufacturing, packing, packaging, transporting, or holding food if such 

use is not intended to have any technical effect in such food.

• Prior to 1997, FDA regulated ion exchange resins under 21 CFR 173.25. Once Congress

established the term “food contact substance” in the Federal Food, Drug, and Cosmetic Act

and initiated the Food Contact Notification Program (FCN) in 1999, all ion exchange petitions 

were converted to this approval method. There was no need to alter or change prior 

approvals under § 173.25, so they were left as is. Since that time, FDA has directed all new 

approvals of ion exchange resins through its FCN program. This clearly reflects FDA’s stance 

that they are food contact substances.

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• FDA maintains a database of approved Food Contact Substances, which include ion

exchange resins that have been classified and approved by FDA as food contact substances.

Additionally, Ingredion submitted comments that echoed the comments from the Organic Trade 

Association:

The regulatory classification for ion exchange resins is both a food contact substance AND a

secondary direct food additive. https://www.fda.gov/foodjfood-ingredientspackaging/foodingredient-packaging-terms: 

• Food Contact Substance (FCS) - Section 409 of the FD&C Act defines an FCS as any 

substance that is intended for use as a component of materials used in manufacturing, 

packing, packaging, transporting, or holding food if such use of the substance is not 

intended to have any technical effect in such food.

• Secondary Direct Food Additive (SDFA) - This term is in the title of 21 CFR 173, which 

was created during recodification of the food additive regulations in 1977. A secondary 

direct food additive has a technical effect in food during processing but not in the 

finished food (e.g., processing aid). Some secondary direct food additives also meet the 

definition of a food contact substance.

The NOSB received no other comments that contradicted that materials could be listed as both a 

secondary direct food additive and food contact substance. It would seem that, even though a material 

might be listed both ways, the fact that they are listed by FDA as a food contact substance, exempts 

those materials from needing to be reviewed by the NOSB and placed on the National List. The 

argument can also be made that if a substance is listed as a secondary food additive, regardless of its 

listing as a food contact substance, that it is under the purview of OFPA and the resins would therefore 

need to appear on the National List. It is beyond the capacity of NOSB members to investigate the 

nuances of FDA rules and regulations and how they legally relate to OFPA. The legal ramifications of 

these decisions should be left to legal counsel for the National Organic Program. 

Subcommittee Recommendation: 

The inherent nature of ion exchange leads us to the conclusion that recharge materials used to recharge 

ion exchange resins must be on the National List if they are used in the processing of organic product. 

These recharge materials leave ions on the resins and those ions will ultimately end up in the final 

organic product. The public comments received at the Spring 2020 NOSB meeting support this 

recommendation. 

There is less consensus on the question of whether the resins themselves must be reviewed and 

included on the National List. From comments received, the resins appear to be classified as both 

secondary food additives and food contact substances, however there are countervailing arguments 

that should be noted. There are legal arguments and interpretations about how OFPA might apply to 

FDA regulations defining secondary food additives and food contact substances. A proposal advising the 

NOP that the resins should not have to appear on the National List was voted down by the full Board at 

the Fall 2020 NOSB meeting. 

Further complicating this issue is that for a material to be classified by FDA as a food contact substance, 

the manufacturer need only submit an application to FDA requesting the classification. If FDA does not 

respond to the application (either denying it or asking for further clarification), the material is 

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automatically added to the food contact substance list. There is no required review by FDA, no public 

comment and, with regard to organic classification, no review of how the material relates to OFPA. Once 

again, this process comes down to a legal opinion as to the interactions of OFPA and FDA regulations 

that is beyond the scope of the NOSB. 

While there was no conclusive evidence in the 2020 TR or public comments that the resins degrade and 

alter the final organic product, this does not mean that there is no evidence. The quote from OMRI at 

the beginning of this document refers to ion exchange resins leaking from columns and thus becoming 

incidental additives. Further research into how and to what extent these resins degrade and whether 

the degradation occurs during the recharge process or during the food filtration process could help shed 

light as to whether these resins are strictly in contact with the organic product or are incidental food 

additives. 

There is also the question of how these resins are manufactured. From the TR, the resins are polymeric 

materials that are synthetic. They are commonly produced as beads, resins, or membranes. Most are 

produced with the polymerization of styrene and divinyl benzene. While the evidence about the 

breakdown of the final resin is not conclusive, styrene itself is listed as a Proposition 65 carcinogen. The 

resins are very similar to plastics. Acidic or basic functional groups are incorporated into the polymeric 

backbone to make the ion exchange resin. 

styrene divinyl benzene

On a less technical level, there is a procedural context as well. Since some physical filtration materials 

are listed and resins are not, there are arguments that there is a disparity in the review of materials. 

There is also some disparity as to the level of scrutiny certifiers apply to reviews of food contact 

substances. Some certifiers require listing all the food contact substances and others may not. 

Regardless of the legal issues, these disparities should be noted and clarified. 

There is also concern from some stakeholders that a de facto statement that resins do not need to be on 

the National List leaves a wide-open playing field for any resin to be used. While resins currently being 

used might be acceptable, the lack of a required review for resins could cause issues in the future with 

resins that would be less acceptable for use in organic production systems. Allowing resin use without 

review could provide an unintentional loophole to the requirements of OFPA.

An alternative to allowing all resins without review would be to create a section on the National List that 

includes all resins used in ion exchange filtration (similar to other broad categories on the List). Petitions 

to the NOSB could be used to annotate this broad listing to exclude problematic resins. This process, 

however, puts the onus on stakeholders to recognize which resins are being used and to act to exclude 

particular resins. A petition to remove a resin could take considerable time and forces the petitioner to 

provide documentation as to how the resin does not comply with OFPA. While this review was

underway, the resin would continue to be used. This is opposite the normal procedures of the NOSB 

whereby the burden is put on the petitioner to document why something should be added to the 

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National List, and that substance is not allowed to be used until it is added. In the past, removal of 

substances already in use can be difficult due to economic impacts of that removal.

The final option is to require each resin to be added to the National List. This would require a petition 

for each specific resin, technical reports to be commissioned and reviewed, and for the Board to 

approve the addition of each resin. This would cause significant disruption to the processing industry 

since these ion exchange filtration practices are already in use and have been for some time. Without a 

long phase-in period, the requirement of listing currently used resins would cause significant economic 

harm. There could also be potential health consequences since some of these filtration processes 

remove heavy metals and other deleterious compounds from organic foods.

While the NOSB would like to give a clear sense of direction on this topic to the National Organic 

Program, the legal issues are beyond the capability of the Board. The allowance of the use of ion 

exchange filtration for many years, without requiring the listing of the resins used, also creates a difficult 

situation. Requiring the listing of these resins could cause significant economic impact and disruption of 

current organic supply chains; however, not requiring listing could leave an unintentional loophole that 

would subvert the requirements of OFPA. These technical and procedural issues are best left to legal 

interpretations and procedural interpretations that are beyond the capabilities of the NOSB.

Subcommittee vote: 

Motion to accept the proposal on ion exchange materials

Motion by: Steve Ela 

Seconded by: Jerry D’Amore

Yes: 6 No: 0 Abstain: 0 Recuse: 0 Absent: 1 

Approved by Jerry D’Amore, Handling Subcommittee Chair, to transmit to NOP February 17, 2021.

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