Quantification of methyl glyoxal in New Zealand Mānuka honey and honey meads

Mānuka honey is New Zealand's (NZ) most globally sought-after honey variety, due to the bioactive effects conferred by methyl glyoxal (MGO). Several NZ meaderies produce Mānuka mead, being a unique NZ product with significant marketing potential; however, it has not been explored in the scientific literature, and MGO has never been quantified in mead of any type. Thus, a versatile HPLC method for the quantification of MGO in both Mānuka mead and honey has been developed, optimised and validated. Two derivatising agents, pentafluorobenzyl hydroxylamine (PFBHA) and o-phenylenediamine were compared, with o-phenylenediamine showing better sensitivity in the mead matrix. To demonstrate the developed method, a survey of the MGO content of commercially available NZ meads was conducted. MGO was detected in four Mānuka meads, with quantifiable levels of 8.20-62.45 mg L^-1 present in three samples; however, its presence may be a result of back sweetening with Mānuka honey.