Hexamethylene tetramine

Hexamethylene tetramine, also known as hexamine or methenamine, is a cyclic organic compound formed by the condensation of formaldehyde and ammonia. As a food preservative it owes its antimicrobial activity to formaldehyde released under acidic conditions: when the compound contacts the acidic environment of certain cured cheeses, it decomposes to release formaldehyde, which inhibits the growth of surface moulds and bacteria. Its use in food is strictly restricted to one application category in the EU: the surface treatment or inner wrapping of Provolone cheese.

JECFA evaluated hexamine in 1967 and established an ADI of 0.15 mg/kg body weight per day expressed as formaldehyde. This very conservative limit reflects the toxicological concerns associated with formaldehyde, which is a known irritant, sensitiser, and at high chronic exposures a carcinogen (IARC Group 1 for nasopharyngeal cancer via inhalation in occupational settings). Dietary exposure from the extremely restricted food use of hexamine is far lower than occupational inhalation levels, but the precautionary ADI reflects appropriate caution.

Hexamethylene tetramine is approved in the EU as E239 exclusively for the preservation of Provolone cheese. Its continued authorisation is based on the importance of this traditional Italian cheese-making practice, the very limited exposure pathway (Provolone surface only), and the absence of safer functionally equivalent alternatives for this specific application. Consumers who wish to avoid formaldehyde-releasing additives should note that E239 is found only in Provolone cheese products and not in other food categories. For most consumers, exposure from this source is negligible relative to the small amounts of formaldehyde naturally present in many common foods including fruit, vegetables, and fermented products.