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E231PreservativeModerate concern
Orthophenylphenol
In plain words
The short version
A surface treatment for citrus and pomes — applied to the skin to prevent post-harvest mold.
Why we flag it amber
It's permitted and generally considered safe, but there are a few reasons to be mindful — like sensitivities in some people, debated studies, or intake limits. The Safety section below explains the specifics.
Safety profile
ADI of 0–0.4 mg/kg body weight (EFSA 2008). Not approved for direct food use. The whole fruit (skin + flesh) consumed quantities of OPP are very low, but the treatment is the reason zest from untreated organic fruit is preferred in cooking. Mild skin and eye irritant in handling.
The detail
Manufactured by hydrolysis of 2-chlorobiphenyl. Originally developed as a wood preservative; adopted as a citrus post-harvest treatment in the mid-20th century to extend shelf life during shipping from tropical producers.
Applied as a wax-or-spray surface treatment on oranges, lemons, grapefruits, apples, and pears to inhibit Penicillium and other post-harvest molds. Typical residue 5–20 mg/kg on the skin. In the EU, E 231 and E 232 are not on the list of authorised food additives; 2-phenylphenol and its sodium salt are regulated there as a fungicide under pesticide law.
White to slightly yellow crystalline solid with a mild phenolic odor. Slightly soluble in water, very soluble in alcohols and alkali (used as the sodium salt for spraying).
In the EU it is approved as a fungicide active substance under pesticide law (current approval runs to 15 November 2027), not as a food additive. In the US, EPA sets residue tolerances for post-harvest use, for example 10 ppm on citrus fruits and 25 ppm on apples and pears. Some EU member states have moved to limit it further.
Sources
- WHO JECFA database — o-Phenylphenol (INS 231), citing the JMPR 1999 ADI — WHO / FAO Joint Expert Committee on Food Additives, 2000. Safety: ADI 0–0.4 mg/kg bw (JMPR 1999)
- European Commission — EU Pesticides Database: 2-Phenylphenol (incl. sodium salt orthophenyl phenol), active substance record — European Commission, DG SANTE, 2026. Regulation and safety: approved in the EU as a fungicide active substance (to 15/11/2027); ADI 0.4 mg/kg bw/day (EFSA 2008)
- Commission Regulation (EU) No 1129/2011 establishing the Union list of food additives — Publications Office of the EU (Official Journal L 295), 2011. Regulation: E 230–E 233 (including E 231/E 232) are absent from the EU list of all authorised food additives
- US eCFR — 40 CFR 180.129 o-Phenylphenol and its sodium salt; tolerances for residues — U.S. eCFR (Office of the Federal Register), 2026. Regulation: US EPA residue tolerances for post-harvest use (e.g. citrus 10 ppm, apple and pear 25 ppm)
Checked against these sources on .
Educational information only. Not medical, dietary or veterinary advice. Spotted an error? Tell us.