Mead Mead is an ancient alcoholic beverage made from fermented honey and water. Recently, mead has come back from the brink of obscurity and seen a global resurgence in popularity. Mānuka honey Mānuka honey contains the potent bioactive compound methyl glyoxal (MGO). MGO has significant and well- established antibacterial properties,1 and is responsible for mānuka honey’s international fame. High MGO-honey’s fetch premium prices in NZ and abroad. Mānuka mead… MGO? In previous qualitative studies, we’ve shown that MGO is not consistently preserved through the fermentation of mānuka honey mead – most of the time it doesn’t survive the fermentation process. To further probe this mechanism, a quantitative method was needed for its analysis. Quantitative method requirements • MGO has been quantified in mānuka honey – but never in mead. We set out to develop an HPLC method. • MGO requires derivatisation to be visible on an HPLC instrument. Two options for derivatising agents, PFBHA2 and o-phenylene diamine,3 have been used From Nectar to Glass: Quantification of Methyl Glyoxal in NZ Mānuka Honey and Mead Survey of commercial NZ meads The method was applied to a survey of all commercially available (explicitly) mānuka (n=8), and three non-manuka meads. Findings Only three of the commercial mānuka meads tested (MM1, MM4 & MM7) contained detectable levels of MGO. MM7 was noted to have been back-sweetened with mānuka honey - honey was added into the finished mead after fermentation. The other samples with MGO, MM1 and MM4, may also have been back-sweetened as they have high sugar content. Conclusions • Our developed method can efficiently quantify MGO in mānuka honeys and meads • MGO is NOT consistently present in mānuka meads –likely does not survive fermentation. Impact Our results show that producers should choose to reserve their more expensive mānuka honey for back-sweetening if an MGO- containing mead is desired. Next steps To further probe the interaction of yeast with MGO, we will apply the developed method to controlled lab-scale mānuka honey ferments – quantify MGO pre, mid, and post fermentation. Influence of: • MGO content of honey used? • Yeast strain? • Fermentation conditions? Comparison of derivatisation methods PFBHA o-Phenylene diamine Sample Preparation: ✓Simple sample prep ✓One hour incubation period ⨯Some phase splitting ⨯Precipitate at higher MGO concentrations ✓Simple sample prep ✓Overnight incubation period ✓Homogeneous samples High Concentration MGO: Low concentration MGO: o-Phenylene-diamine method selected due to better performance at lower MGO concentration (greater sensitivity), and fewer sample prep issues. Subsequently, the method was optimised at all steps: • Sample preparation • Incaution period/derivative stability • HPLC instrument method Then assessed for sensitivity: ✓LoQ = 0.58 mgL-1 in honey, 6.35 mgL-1 in mead And repeatability: ✓Experimental recovery 98-103 %, %RSD <4.5% Honey type MGO (mgL-1) Sugars (g L- 1) MM1 Mānuka 4.11 110.3 MM2 Mānuka Not detected 9.0 MM3 Mānuka Not detected 0.4 MM4 Mānuka 7.50 85.6 MM5 Mānuka Not detected 18.6 MM6 Mānuka Not detected 49.3 MM7 Mānuka 19.86 41.7 MM8 Mānuka Not detected 43.6 RM1 Rewarewa blossom Not detected 41.2 KM1 Kāmahi blossom Not detected 1.9 PM1 Pōhutukawa blossom Not detected 9.1 Claire Webstera, Rebecca Deedab, David Barkera, Lisa Pilkingtonac a) School of Chemical Sciences, The University of Auckland Waipapa Taumata Rau b) School of Biological Sciences, The University of Auckland Waipapa Taumata Rau c) Te Pūnaha Matatini References 1) J. Apic. Res. 1988, 27 (1), 62–67. https://doi.org/10.1080/00218839.1988.11100783 2) PLoS ONE 2016, 11 (11), e0167006. https://doi.org/10.1371/journal.pone.0167006. 3) Carbohydr. Res. 2008, 343 (4), 651–659. https://doi.org/10.1016/j.carres.2007.12.011.