In August 2024, maple sap was vacuum harvested from one of the coppiced trees in the test plantation near Hanmer Springs.
Sap was collected over the course of three days during a freeze-thaw event, when the South Island was experiencing a ridge of high-pressure, bringing with it snowfall.
The chosen tree was cut at about ~1 m above ground level. Sap extraction was performed with a custom-built vacuum fitting (see figure and video below), assembled from readily available materials. Sap was collected in a liquid separation container, with coarse volumetric measurements every 10 mL. A hand-operated vacuum pump supplied the vacuum. Check out the video below to see the vacuum harvest in action!
About 40ml sap collected over two 3 hour periods …when the vacuum was working as planned! There were some issues - minor leaks in the connection to the stem were found which reduced the vacuum and sap collection eventually stopped as the pressure returned to atmospheric pressure.
This experiment indicates that extracting sap from the top of a maple sapling using a specialised sap-collection device and vacuum extraction is a viable approach and can be used in New Zealand. We are working on data analysis to characterise the chemical composition of the sugar maple sap collected, and will share more information in an upcoming journal paper that will summarise this study.