Forecasting models can be used to estimate the way that concentrations of DHA, MG, and HMF in mānuka honey will change in the future. However, sometimes a forecast is not available when looking at a set of test results for honey.

The ratio of DHA to MG in honey can be used to give a quick indication of its potential to ‘grow’ (the increase in MG concentration) over time. While not as good as a forecast for working out how a honey may change in future, it can be very helpful.

How to calculate a DHA to MG ratio The ratio of DHA to MG (DHA:MG) is calculated as follows: DHA concentration (mg/kg) ÷ MG concentration (mg/kg) = DHA:MG For example:

• a honey with 1,200 mg/kg of DHA and 120 mg/kg of MG has a DHA:MG ratio of 10:1 (or 10 times as much DHA as MG in the honey)
• a honey with 425 mg/kg of DHA and 150 mg/kg of MG has a DHA:MG ratio of 2.5:1 (or 2.5 times as much DHA as MG in the honey).

Why DHA:MG is useful As described in the article on forecasting models in the July 2020 issue (Howse, 2020), DHA in honey (which comes from the nectar bees collect from mānuka plants) converts to MG over time.

However, at the same time, the MG in the honey is also changing to other things. When there is a lot of DHA in the honey relative to MG (a high DHA:MG ratio), the rate at which DHA is converting to MG will be faster than the rate at which MG is changing to other things. So the MG concentration goes up.

As the amounts of DHA relative to MG reduce, more of the DHA is required simply to make up for the MG changes and so the rate of increase in MG concentration slows down. Eventually there is only enough DHA to maintain the MG level, and after that you tend to see a decline in MG concentration.