12
NEW ZEALAND BEEKEEPER, DECEMBER 2016
TESTING NECTAR TO SELECT MANUKA TREES FOR HIGH-GRADE HONEY RESEARCH
Dr Megan Grainger, Operations Manager–Food Division, Analytica Laboratories
Testing of mānuka nectar is a practical method to identify mānuka (Leptospermum scoparium) plants that will contribute to higher-grade mānuka honey. Results can be used to rank the plants according to the dihydroxyacetone (DHA) and Leptosperin content of the nectar.
The benefit of nectar analysis Methylglyoxal (MG) is the compound in mānuka honey responsible for the non-peroxide activity (NPA). MG is formed from the conversion of dihydroxyacetone (DHA). A hive of bees will visit many flowers from various trees which will dilute the overall DHA and Leptosperin in a batch of honey; hence the more mānuka trees with high DHA and Leptosperin that are in the flight range of the hive, the higher the maximum MG value (and NPA) will be. At present, little information is known about the pathways of expression for both DHA and Leptosperin in the nectar, but the concentration of both compounds is known to vary between Leptospermum species. There is considerable interest from nurseries, landowners and beekeepers to find varieties of mānuka that express high levels of DHA. Collecting the sample Analysis of nectar requires representative samples of each tree to be collected; one sample is created by combining the nectar of 10 flowers from one tree. There are three recommended sampling techniques; these are summarised in Table 1. The more care that is taken when collecting a sample, the more reflective the results will be of the tree. Key considerations when sampling are to ensure that there is visible nectar on the flowers (Figure 1) and that it has not recently rained. It is recommended that a fine-mesh bag is placed over the branch a day before sampling to keep insects off the flowers; a plastic bag may cause condensation to form which will dilute the nectar.
Table 1. Overview of three nectar collection techniques.
Sampling Method
Advantages
Disadvantages
Direct Method Collect pure nectar from 10 flowers into one tube
• Preserves flower • 100% nectar
• Impractical in-field • May produce very small sample volume • May dilute sample too much • May introduce extra sugars • Multi-step technique • Time consuming
Wash Method Take 10 flowers from tree and place in a tube with 1.5 mL water 10x10 Method Dissolve nectar on flower using 10 µL water; repeat for 9 flowers into same tube
• Quick and easy • Practical
• Sufficient volume for analysis
Figure 1. Visible nectar on a mānuka flower.
Made with FlippingBook - professional solution for displaying marketing and sales documents online