In honey, hydroxymethylfurfural (HMF) is used as an indicator of aging and heat treatment. HMF is commonly tested for as part of the mānuka 3-in-1 test along with DHA (dihydroxyacetone) and MGO (methylglyoxal). International standards, including CODEX, specify that honey should contain no more than 40 mg/kg of HMF (Codex Alimentarius Commission, 2001).