Refinement of birch sap

June 23, 2023

Beyond maple syrup, one of the goals of our research is to explore the potential to produce syrup from NewZealand-grown birch trees (e.g. Betula papyrifera). Birch syrup is a niche product, considered a delicacy in the culinary industry.

Birch isn’t a competitor or substitute for maple syrup, as it has a very different flavour. It’s commercially attractive because, although the market is smaller, birch syrup sells for 3-4 times the price of maple syrup. Also, birch sap flow tends to occur at the end of the maple season, so having both syrups in production extends the use of existing sugaring equipment and infrastructure.

Credit: istock.

Birch sap-to-syrup conversion

However, birch syrup takes a greater amount of effort to produce in comparison to maple syrup. One litre of birch syrup requires 100 litres of sap, compared to 40 litres for maple syrup. This is because the sugar content of birch sap (0.5–1%) is lower than that of maple sap (2–2.5%). This difference, as well as differences in sap composition, mean that the processing of birch sap is similar but different to maple sap-to-syrup conversion.

To remove water content from tree sap, the first step in modern processing methods is reverse osmosis, which uses pressure to force sap through a membrane that is only permeable to water. This means the sugar content, and other flavour components, are concentrated in the remaining sap.

For maple syrup, time and heating is a critical step for the development of flavour, colour and density. So, reverse osmosis is used to remove about half the water content in maple sap (the sugar content increases to 8% -16%) before an evaporation step is used to caramelise the sugar and add colour. Syrup has a sugar content between 66-68%.  

Conversely, for birch syrup, time and heat are detrimental.

Prolonged exposure to heat causes birch sap to develop a very strong and unappealing molasses-like flavour. This is because birch sap sugar is made up of fructose and glucose, while the sugar in maple sap are mostly sucrose. Fructose and glucose react at much lower temperatures. So, birch syrup is typically processed through a reverse osmosis unit to remove 90% of the water, followed by a short evaporation time to caramelise the fructose for developing flavour and colour.

Differences in sap sugar composition between maple and birch trees.

Birch syrup research

A series of undergraduate research projects at the University of Canterbury have investigated the use and economics of reverse osmosis for the refinement of maple and birch saps. These projects have investigated how the sugar concentration of the sucrose solution, maple sap and birch sap affect the reverse osmosis flux. And conversely, how flow rate, pressure and temperature conditions of the reverse osmosis method affect sugar concentration.  

Our birch syrup research is ongoing. The next steps (over several years) include:

  1. Working with a landowner to establish a birch test plantation so that we can understand the yields using the plantation method: sugar content and total volume.  This will take time to establish.
  2. Furthering research on the evaporation conditions, for example, trialling evaporation under vacuum to decrease the evaporation temperature and reduce reactions of the fructose and glucose.
  3. Understanding the mineral content from birch sap obtained from different locations as these affect the flavour (like terroir in wine).


Business Case & Economics
Equipment & Processing