Science Friday Podcast Recap: The Sticky Science Behind Maple Syrup

On a recent episode of the Science Friday podcast with host Ira Flatow, he and his guest Dr. Abby van den Berg - a research assistant professor of plant biology at the University of Vermont - discussed the science behind maple syrup as well as her new way of extracting syrup from maple trees. According to Dr. van den Berg, the sap that is the pivotal ingredient in maple syrup is predominantly water with 2% sucrose - in other words, a little bit of sugar and water. This sap is made in maple trees as a result of the cycle of above and below freezing temperatures in the zones in which they are grown. When temperatures are below freezing, water is taken up from the soil into the fine branches of the tree. When temperatures are above freezing, atmospheric pressure develops within the tree. That atmospheric pressure is what allows sap harvesters to obtain the sap. The flavor of the maple syrup then comes from the reactions that take place when heat is applied as it is concentrated from sap to syrup. The color as well as some of the flavor also comes from the microorganisms that feed on the sap and produce glucose and fructose in the process. Though the most-practiced method of sap retrieval is the drilling of a hole into a tree and insertion of a spout into the tree that extracts the syrup, Dr. van den Berg has come up with a new method. In her method, she cuts off the top of a sapling, plugs a pump into the top of the stump, and sucks out the sap. She said that she does not intend to replace the current method, but rather add a beneficial tool to sap harvesters' toolboxes.