Sap flow and syrup crop update

The sap harvest and syrup processing season has been delayed this year similar to 2014. While sap is flowing nicely in early areas, producers in later areas further north began to see sap flow this past week.   Not to be discouraged, remember the season in Ontario varies by 2 to 3 weeks on average, from earliest to later regions.

Maple syrup producers in early southwest areas, the Carolinian sugar bushes, are content to be harvesting sap in larger quantities this week. The sap sugar concentration began very low at many operations from less than 1.0 to 1.5 ⁰Brix. With each sap run, the sugar has increased as expected, and this past week sap sugar concentrations of 2 to 3 ⁰Brix are being harvested.

In the Chatham-Kent area over to Niagara region, producers report a range of 50 to 80% of a syrup crop has been boiled so far. Mainly light syrup has been processed, with the first medium grade syrup appearing during the past week. A few sites have boiled only medium so far with no light grade.

Grey-Bruce east to Quinte and over to Lanark, producers have boiled 10 to 25% of a syrup crop with light and medium grades.  Areas north from Haliburton-Kawartha to Bancroft report they are still waiting for the first really good sap runs, ranging from 1 to 5 small sap runs and batches of syrup.  Weather in the Bancroft area has not been conducive to sap flow.  Lanark and eastern counties began sap harvest during the second week of March where producers were tapped and ready.

Photo 1, 2 & 3.  Snow cover remained in most sugar bushes across the province, a little still in the southwest, while snow is still deep in central and north-region sugar bushes. Centre photo, a sap-cicle leaking from a branch wound is often sweeter than fresh sap, where some water has evaporated away.  On the right, a blocked frozen drop line with sap leaking then freezing, due to sap pressure inside the tree.

 Photo 4 & 5. A sugar maple on the left and maple sugar is on the right.  A quick reminder of where all our maple products come from, and other values of maple trees.  Granular maple sugar is ‘pure maple’ and makes a great culinary sweetener.

Metabolism in sap

When winters are long and very cold and have no episodes of thawing, the first sap flow may sometimes be off-flavour. Maple researchers believe the off-flavour is caused by a buildup of amino acid in the maple trees, which normally would dissipate during winter thaws.  Researchers refer to this off-flavour as ‘tree metabolism’.   Syrup made from off-flavour sap will have an unpleasant flavour, which cannot be blended out with good syrup. Commercial producers usually discard the first sap run and consider it only useful for rinsing their sap lines.

Filtering syrup

Maple syrup is filtered of all sediment as it comes hot off the evaporator.  Some producers pass the syrup through a filter twice to ensure the syrup will be very clear, without any cloudiness.  Glass containers show the clarity of properly filtered syrup, and is equally clear in plastic jugs and cans.

This season, some syrup producers are finding larger amounts of natural sediment, often called niter or sugar sand, present in the sap as it concentrates down into syrup. Ease of filtering syrup can change every year and with each batch of syrup.

Photo 6 & 7.  A simple cone filter with layered liner filters is ready to clean the syrup of sediment. As the filter slowly fills with sugar sand and filtering slows, the top liner is removed to expose a new clean filter. On the right, a flat cloth filter with layered paper filters is ready to clarify the syrup as it comes off the evaporator. Only use food grade stainless steel or food grade plastic containers to handle filtered syrup.

Photo 8 & 9.  A plate filter press is commonly used in larger operations.   Models having additional plates or larger plates are available, depending on the quantity of syrup and the desired speed required to filter each batch of syrup. Right photo: A transparent plate filter enables the operator to see the hot syrup flowing and to help determine, in addition to monitoring pressure, when the plates require cleaning.

To operate a filter press, new filter papers are aligned between each plate and the plates are pressed tightly together with threaded bolts. Before syrup can be filtered, the hollow plates in the press are pre-loaded with a layer of filter aid. Filter aid is food-grade diatomaceous earth, which catches sediment as fresh syrup passes through the press. 

Photo 10 & 11. Aligning new filter papers between each plate.  On the right, securing the plates tightly together to prevent leaking of pressurized syrup during filtering.

Photo 12 & 13. Mixing a few gallons of hot maple syrup with filter aid prior to loading the hollow spacers between filter plates.  A large whisk helps to mix the dry filter aid powder with hot syrup.  Consult equipment dealers on how much filter aid to mix with syrup for the particular size of filter press.

Once the filter aid is loaded, the remaining syrup is pumped through the filter.  All sediment is removed as the hot syrup passes through the diatomaceous layer and paper.  The operator monitors the pressure of the syrup as it flows through to know when the filter needs to be cleaned of sugar sand.

Photo 14.  A cylinder syrup filter operates similar to a plate filter press under pressure, where a cloth or paper filter and filter aid powder are pre-loaded onto an inner cylinder to provide filtration of sediment, resulting in clear maple syrup.

The best way to learn the details of proper filtering of maple syrup is to attend a demonstration by maple equipment dealers.  Watch for upcoming workshops, or attend the Maple Summer conference and tour in July 2015, presented by the Ontario Maple Syrup Producer’s Association.

The Jones Rule of 86 has been revised

Back in 1946, a researcher named C.H. Jones developed a simple formula to determine the quantity of sap required to make one gallon of maple syrup, which factored in the concentration of sugar in the sap (University of Vermont Proctor Maple Research Centre). 

Basically the rule says: divide the number 86 by the sap sugar concentration to tell you how much fresh sap will be needed to get one gallon, or one litre of maple syrup. Many producers still use this method.

Photo 15.  A display at a maple syrup festival visually shows a ball-park estimate of the number of pails of fresh sap that are required to make 1 pail of syrup.  A 40 to 1 sap-to-syrup ratio is commonly presented.

But nothing ever seems to remain simple.  It was realised more recently that the simple Jones Rule of 86 was devised historically when the concentration of finished maple syrup was 65.5 ⁰Brix.  The regulated minimum density for maple syrup in Ontario currently is 66.0 ⁰Brix, and further, many producers aim to finish their syrup at 66.9 ⁰Brix for best quality.  A new formula was needed.

Old math: The formula for the old Jones Rule of 86.  For example, if sap sugar is 2 ⁰Brix, then 86 ÷ 2 = 43 litres of sap.   You will need 43 litres of 2 ⁰Brix sap to make 1 litre of ‘concentrated sap’ having a density of 65.5 ⁰Brix.  The syrup can’t legally be called maple syrup because it falls below 66.0 ⁰Brix.  Keep boiling a little longer.

New math: The revised Rules of 87.1 and 88.2, to determine the amount of sap required to make maple syrup that will have a finished density of 66.0 and 66.9 ⁰Brix, respectively.

Precision matters to many modern maple syrup producers.  The amended formula may seem trivial when determining ratios of fresh sap to syrup, however, where producers are now using reverse osmosis and are selling sap that may be concentrated to higher sugar concentrations, e.g. 8 to 20 ⁰Brix, the accuracy of the calculation becomes important for high-value sap.