An investigation of the accelerated loss of diastase (α-amylase) activity in mānuka honey

Abstract Diastase (α-amylase) activity, an international indicator of improper storage or heat treatment in honey, must be > 8 diastase number (DN) to meet export requirements. Mānuka honey, globally valued for unique antibacterial activity, more readily fails the test despite proper storage. To investigate the accelerated activity loss, two mānuka honeys plus clover with methylglyoxal (MGO), dihydroxyacetone (DHA) and/or 3-phenyllactic acid (3PLA) added were stored (27 °C, 200 days). Activity loss varied with the compounds present; decreasing faster when 3PLA was added with MGO or DHA. Changes in substrate binding indicated diastase activity loss was not exclusively due to denaturation but that protein modifications from compounds in mānuka honey affect enzyme-substrate binding affinity, lowering enzyme activity independent of enzyme denaturation. This research highlights that diastase activity is not a suitable indicator of excessive heat treatment for mānuka honey due to the interactions of mānuka-specific compounds that inactivate the enzyme irrespective of temperature.