Orthophenylphenol
The short version
A surface treatment for citrus and pomes — applied to the skin to prevent post-harvest mold.
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.
Where it comes from
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.
How it's used
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. The fruit must be labelled as treated with E231 (or its sodium salt E232) in the EU and UK.
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.
Physical & chemical properties
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).
Regulation worldwide
Permitted in the EU, US, and most jurisdictions as a citrus post-harvest treatment with mandatory labelling. Some EU member states have moved to limit it further.
Educational information only. Not medical or dietary advice.