Metatartaric Acid
The short version
A polymerized form of tartaric acid — added to wine to prevent cold-temperature tartrate crystallization.
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Where it comes from
Produced by controlled thermal polymerization of L-tartaric acid (E334). The resulting polymer has limited stability — slowly hydrolyzes back to tartaric acid in solution.
How it's used
Specifically added to wine and some fruit beverages to delay the precipitation of potassium bitartrate crystals ("wine diamonds") that otherwise form on chilled storage. Typical addition 100 mg/L. A transient stabilizer — its protective effect lasts months, not years.
Safety profile
ADI not specified — treated like tartaric acid in metabolism (hydrolyzes during digestion). Same negligible toxicity profile.
Physical & chemical properties
Yellowish glassy or fibrous solid. Soluble in water. Hygroscopic and slowly hydrolyzes — must be added shortly before bottling.
Regulation worldwide
Permitted in the EU for wine and beverage applications.
Educational information only. Not medical or dietary advice.