Reverse osmosis (RO), also termed hyperfiltration, is an effective alternative to save energy usage by 60-70 percent, reduce time and improve the product quality in commercial maple syrup production. Traditionally used for water desalination, RO is a filtration technique used in sugaring maple syrup, in which maple sap is filtered through a semi-permeable membrane filter under high pressure before introducing the syrup into an evaporator. This method allows removal of excess water from the maple sap by 75-80 percent, increases the sugar percentage in the syrup and concentrates it.
Identify the tree that needs to be tapped for collecting maple sap. Yield depends on the type of maple tree, its diameter and the weather. Traditionally, hard maple trees, also known as sugar maple trees, have been the preferred choice for sugar makers as these trees yield 1 gallon of maple syrup for every 40 gallons of collected sap. For tapping, a maple tree diameter should be at least 10 inches. The best time to collect maple sap is spring when the temperatures oscillate around 40 degrees Fahrenheit.
Use a drill unit to drill a 7/16-inch wide and 2-inch deep hole in the maple tree trunk with a slightly upward angle. Insert a plastic tap or spout into the hole and connect it to the plastic tubing. This tubing is interconnected with plastic tubes from other maple trees, which together are connected to a vacuum pump. The presence of a vacuum increases sap flow.
Connect the vacuum pump to a filtration unit, which allows debris removal from the collected sap, which is then collected in storage tanks. At this stage, the sugar percentage in the maple sap will be 1.5-2 percent.
Connect the storage tank to a feeder tank, which is connected to a RO filter unit. The feeder tank pumps the maple sap into the RO filter unit at a high pressure. The RO unit contains a specially designed semi-permeable RO membrane filter that can withstand high pressure. The pores of the membrane allow only water molecules to pass through and retain sugar and other large molecules on the surface. This method allows removal of substantial amount of water from the sap. The sugar concentration at this stage is 5-6 percent.
Feed the maple sap coming from the RO filter unit to an evaporator. The sugar concentration of the sap after evaporation will be 67 percent. Filter the maple syrup using a filter press and package it in a sterile container.
Rinse the RO membrane with deionized water after every use to achieve optimum efficiency.
Store RO membrane in a hermetically sealed container containing water. The addition of sodium metabisulfite to the water prevents fungal growth on the membrane.
Remember to clean the reverse osmosis equipment thoroughly using an anti-bacterial solution and clean water to avoid contamination.
Never use bleach to clean RO membrane filters