E285

Borax

Moderate risk preservativesynthetic

Permitted only for caviar in the EU.

Acceptable daily intake: 0.16 mg/kg body weight/day (EFSA)
Vegan: Yes
Vegetarian: Yes

What it is

E285, commonly known as Borax, is the sodium salt of boric acid (E284). Like its parent compound, its use as a food additive is strictly limited to preserving genuine sturgeon caviar due to the toxicity of boron accumulation.

How it is used in food

Preserves sturgeon caviar.

Commonly found in

Genuine sturgeon caviar

Health and safety

Restricted heavily because boron accumulates in the body.

Boron compounds are toxic to the reproductive system if consumed in high doses. While EFSA has established a safe Tolerable Daily Intake, the primary strategy to protect the public from boron accumulation is to ban it in all foods except a luxury item that is eaten in tiny, infrequent quantities.

Reproductive toxicity

general population · evidence: established

Animal studies show that excessive exposure to boron compounds can impair fertility and fetal development. Its strict restriction in food prevents this risk in humans.

EFSA re-evaluation of boric acid and sodium tetraborate

Shares its single EU exemption with boric acid.

Regulatory status

Region	Status	Notes
Australia & New Zealand FSANZ	Permitted	Permitted under the FSANZ Food Standards Code.
European Union EFSA / European Commission	Permitted	Authorised for food use under EU regulations (Annex II).
United States FDA (Food and Drug Administration)	Banned	Not approved for use as a food additive. “Banned”

Identification on labels

E-number: E285

How it is made

It is naturally occurring and mined from evaporite deposits, then purified.

Mining and Purification — Borate minerals are mined, dissolved in water, filtered, and recrystallised to produce pure borax.

Worth knowing

Everywhere else it’s a cleaning-product ingredient, not a food one.

Conclusion

Unless you frequently consume real sturgeon caviar, you will never encounter E285 in your diet. Its approval exists merely to support a highly specific, traditional luxury food industry.

References

EFSA re-evaluation of boric acid and sodium tetraborate — EFSA

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Entry last reviewed 2026-07-28.

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