Maple sugaring and the science of sap flow

Transcription

1 Maple sugaring and the science of sap flow Photo by: Paula Murakami What makes this possible? The Science of Sap Flow and Maple Syrup Production 1

2 Basic physiology of maple sugaring Maple syrup production possible - 2 unique properties of maple trees: Ability to generate positive pressure in xylem sap (Allows sap to flow) The high sugar concentration in spring xylem sap Basic physiology of maple sugaring Must also have the right weather conditions for sap to flow! Freezing nights followed by warm days Phloem Photosynthate (sugar) from source to sink Xylem Water from soil to leaves (usually not sugars!) 2

3 Air temperature Xylem Sap sugar Nov 1 Jan 1 Mar 1 May 1 Vessel Ray cells containing starch Fiber cells Sugar maple cross section The sap flow mechanism in maple: Freezing and thawing temperatures are required 3

4 Freezing causes liquid to expand Why doesn t sap exude during a freeze and shrink during a thaw? Sugar maple wood section Vessel Fiber cells air filled in maple Ray cells containing starch Vessel with sap Temperature: Above freezing for hours or days Air-filled fibers 4

5 Vessel with sap Air-filled fibers Ice crystal growth (frost) occurs inside the air-filled fibers as the branches freeze. The water is supplied by the sap in the vessels. Vessel with sap Temperature: Falling from above freezing to just below freezing Air-filled fibers Generates ( ) pressure Vessel with sap Temperature: Below freezing for several hours or days. Air-filled fibers 5

6 Vessel with sap Temperature: Rising from below to above freezing. Air-filled fibers Generates (+) pressure! Temperature ( o C)and Pressure (psi) Sap pressure to psi -5 psi Pressure Branch temperature March 20 March 21 March Temperature and pressure in the spring in untapped trees But why does sap flow when we put a hole in the tree? 6

7 Sap pressure = 15 psi Air pressure = 0 psi Sap Atmospheric pressure lower than inside the tree ~ sap flows out of the wound! Figure by: Tim Wilmot Maple syrup production Sap collection Photos by: Brian Stowe 7

8 Sap collection Trees are tapped with cordless drills and plastic spouts are most common Photos by: PMRC Sap collection Photos by: PMRC Sap collection Network of 5/16 plastic tubing connects to larger mainlines 8

9 Sap collection Sap flows from the network of mainlines into the sugarhouse Sap collection Many producers add vacuum to their tubing systems Adding vacuum Sap pressure = 15 psi Vacuum Air pressure (15 Hg) = 0 = psi -7.5 psi Figure by: Tim Wilmot 9

10 Filtering Solid material Microorganisms After sap is removed from lines it is often filtered by UV light Photo: Tim Wilmot Sap storage Sap is stored in large tanks for as short a time as possible Photo by: PMRC Reverse osmosis Raw sap is ~2% sugar RO concentrates sap (8-10%) without heating Reduces: Evaporator fuel costs Boiling time Photo by: PMRC 10

11 Reverse Osmosis % Sugar Boiling Evaporators Many types Fuel types Wood Oil Photo by: George Cook Evaporator basic anatomy Back Pan Front Pan 11

12 Evaporators Back pan Where sap comes in Sap inlet Back Pan Deep flues facilitate heat transfer Front Pan From 2-~8% Syrup Drawoff Evaporators Sap inlet Back Pan Front pan Where syrup is made Several compartments From 8 to 65% Front Pan Syrup Drawoff Boiling Syrup Draw-off 12

13 Get to appropriate density before packing If too high: Crystallization Finishing If too low: Fermentation, mold, bacteria Photos by: Tim Wilmot Filtering and packing Syrup must be filtered to remove solids and make a clear product Photo by: Brian Stowe Filtering and packing Filtered syrup is hot-packed into drums or smaller containers Photos by: PMRC 13

14 Grading Syrup is graded on four criteria: Color Flavor Density Clarity Photo by: Mark Isselhardt Color is primary determinant, but all syrup must meet the other standards, too Grading Different grading systems VT US Canada Different names, but similar standards Photo by: Mark Isselhardt Only pure VT syrup can be labeled as VT syrup with a VT grade Color Grading Based on % light transmittance (at 560nm) Temporary Grading Kits Permanent Grading Kits Grading meters Photos by: Mark Isselhardt 14

15 Density 66.9% minimum in VT Refractometers Hydrometers Photos: PMRC Vermont Maple Syrup Grades ~ Vermont Fancy ~ Light amber color and a delicate maple bouquet. A mild maple flavor, excellent on foods such as ice cream which permit its subtle flavor to be appreciated. ~ Grade A Dark Amber ~ Dark amber color and a robust maple bouquet. This hearty maple flavor is very popular for table and all around use. Is often used to add flavor when cooking. ~ Grade A Medium Amber ~ Medium amber color and a pronounced maple bouquet. Characteristic maple flavor, that is popular for table and all around use. Great on pancakes and french toast. ~ Vermont Grade B ~ The strongest and darkest grade of maple syrup. Primarily used for cooking and also popular for the table. Makes a great substitute for other sugars in baking. 15

16 University of Vermont Proctor Maple Research Center Underhill Center, Vermont Department of Plant Biology, College of Agriculture & Life Sciences Proctor Maple Research Center Maple research conducted at UVM since 1890s PMRC established in 1946 Photos: PMRC UVM Proctor Maple Research Center Martin Block (High Yield Study) Sap Shed Red Series (Strategies Study) * N Main Bush (Equipment Sugarhouse * Comparison PMRC Lab Study) * 16

17 UVM Proctor Maple Research Center Mission: Maple Research Extension/Outreach Demonstration Current Research at PMRC 1. Increasing productivity and profitability of maple syrup production Maximizing Sap Yield Typical yield much lower than maximum attainable: < gal/tap (buckets vacuum tubing) vs (ideal conditions) Innovations to Maximize Sap Yield 17

18 1. Increasing productivity and profitability of maple syrup production Birch Syrup Production in maple operations Existing equipment, trees, and infrastructure Valuable ($) product 2. Environmental and management impacts on the maple resource Sustainability of maple syrup production depends on healthy trees Impacts of increased carbohydrate extraction on tree health Reassessment of tapping guidelines Describe and mitigate effects of climate change on maple syrup production 3. Maple syrup chemistry and quality Descriptive chemistry Maple syrup contamination, adulteration, legal issues Impacts of processing technologies on maple syrup chemistry and flavor 18

19 3. Maple syrup chemistry and quality Impacts of processing technologies on syrup chemistry and flavor Integrity of maple syrup characteristic attributes is essential! Technology rapidly evolving, effects of new technologies often untested RO, Air injection, etc. What are the effects on syrup chemical composition and flavor? 3. Maple syrup chemistry and quality Impacts of processing technologies on syrup chemistry and flavor Controlled experiments to test impacts of technologies on syrup quality: Chemical composition Flavor UVM Maple Production Research Facility 19