Many of the larger maple syrup operations have completed tapping their sugar bushes, thanks to mild weather last week and spring-like conditions over the past weekend. Many medium and smaller producers have not completed tapping their trees and have decided to wait until the coming weekend, or wait for next week to see what the extended weather forecast predicts. Very cold weather has currently placed sap harvest on hold. Sugar bushes in central and northern regions remain deeply frozen.
Where maple trees in untapped sugar bushes are deeply frozen again, producers should wait until the next thaw before drilling tap holes and setting spouts. Frozen bark and underlying sapwood can split very easily above and below the tap hole if drilling and setting spiles is done while trees are frozen. Trees that are deeply frozen can require several days of thawing temperatures before the underlying sapwood is above – 5 ⁰C and is safe for tapping.
Sap flow predictions
Southwestern Ontario and southern regions along the Great Lakes and Saint Lawrence River can be prepared for sap flow over the coming weekend and early in the coming week. Thawing conditions are expected and may induce sap flow, although a lack of sufficient freezing nighttime temperatures may limit the quantity of sap yield in the southwest. Sap flow is not likely to occur next week in central and northern regions, since daytime temperatures may not be warm enough to thaw sap, and nighttime temperatures will be cold to keep the trees frozen.
Measuring syrup density
In Ontario, the minimum legal density of dissolved sugar and solids in finished maple syrup is 66.0 ⁰Brix. Where the density is below 66 ⁰Brix and does not meet the legal minimum, it cannot be called maple syrup and would instead be called concentrated sap.
Achieving a minimum density of 66 ⁰Brix is also a measure of quality for maple syrup. Many syrup producers voluntarily concentrate their syrup higher to 66.5 to 67.0 ⁰Brix because they, and many customers, prefer the thicker viscosity and improved mouth-feel achieved by boiling it down a little extra. Where density becomes too high, dissolved solids, mainly sucrose, will precipitate out as crystals or as solid residue, which can de-value the product.
Another important factor for accurately measuring syrup density to a minimum of 66 ⁰Brix is to help prevent growth of spoilage organisms from contaminating the finished syrup, such as moulds of fungi or yeast. Mould spores require free water in foods to germinate and grow. In properly made maple syrup, much of the water content will be bound up by sugar and other dissolved solids, so less free water is available for mould to establish.
Measuring boiling point elevation from sap to syrup
Using boiling point elevation to measure sugar concentration is well adapted to processing maple sap into maple syrup. Finished maple syrup will boil at 104.1 to 104.2 ⁰C (219.3 to 219.5 ⁰F) to achieve a density of 66.5⁰ to 67⁰ Brix, respectively.
To ensure accuracy of sugar concentration readings during boiling, it is necessary to understand how to calibrate mechanical and electronic thermometers that are used during maple syrup processing. For example, dial thermometers are popular among producers.
Dealers of maple equipment are a wealth of knowledge on many aspects of maple syrup production, including density measurement. There are various devices available, having a range of costs, to measure the density of sap and maple syrup. Producers can decide for themselves the best device(s) to use.
Using a hydrometer (preferred) or a hydrotherm
An accurate hydrometer measurement requires a density correction, which is determined from the temperature of the syrup sample. See the following example, where the syrup sample initially appears to be below the legal minimum density of 66.0 ⁰Brix, however with density correction, the syrup is above the minimum legal density and should have an ideal ‘mouth feel’ viscosity.
Resetting a digital refractometer to 0.0 ⁰Brix (set zero)
Verifying the accuracy of density readings