to view a PDF of the - National Maple Syrup Festival

Recommendations

Info

FEATURE REVERSE OSMOSIS PRESSURE VESSEL Courtesy of Dr. Gary Graham, Ohio State University Extension, Wooster, Ohio. 26 NATIONAL BOARD BULLETIN / FALL 2008 nationalboard.org
CAROL DAVIDSON COOKING PANCAKES at The National Maple Syrup Festival. Osmosis is the natural diffusion, without pressure, of a solvent through a semipermeable membrane from a solution with low solute concentration to a solution with high solute concentration. On the other hand, reverse osmosis uses high pressure to force a solvent from an area of high solute concentration through a membrane to an area of low solute concentration. It was achieved in 1959 when a UCLA professor, Samuel Yuster, and two of his students, Sidney Loeb and Srinivasa Sourirajan, trying to find a way to extract pure water from salt water, produced a synthetic membrane from cellulose acetate polymer. The membrane rejected the salt, but let the water pass. The operating pressures of the membrane ranged from 800 to 1,000 lb/in! for sea water and 200 to 400 lb/in! for brackish water. Today reverse osmosis is the most efficient way of ridding both salt and fresh water of impurities. And, as maple syrup producers have found out, an efficient way of capturing them. Straight from the tree, sap has a sugar content of 2 percent; to increase the content to 67 percent (or, to turn sap “into thick, sweet syrup that piques the palate”), producers must reduce the water. “Reverse osmosis,” Burton says, “is a process we do with the sap before it even gets to the evaporator. What we do is discard the water and capture the impurities – we want the impurities, the sugar. What happens when you filter the sap is you go from 2 percent sugar content to 4 percent; then if you filter it again, you go from 4 percent to 8 percent. Some producers are even going from 8 percent to 16 percent before it goes to the evaporator.” nationalboard.org DRAWING OFF A BUCKET OF 100% PURE MAPLE SYRUP. According to Dr. Timothy Perkins, director of the Proctor Maple Research Center at the University of Vermont, reverse osmosis uses pump-generated pressure to push water through a membrane in a high-pressure chamber. “The sugar in sap can’t pass through the pores in the membrane, so it’s retained and concentrated; however, the water does pass through the membrane and is discarded or used for washing or rinsing cycles.” Perkins says reverse osmosis pressure vessels generally work under a maximum pressure of 200 to 300 psi, though that can vary greatly depending on the vessel and membrane. Reverse osmosis as a viable method for the concentration of sugar in sap was first tested in 1966 at the USDA Maple Research Laboratory. The first reverse osmosis system was installed in 1971; by the early eighties, a total of about 100 machines were operating in Canada and the US. Something producers need to be wary of when using reverse osmosis is the contamination of the membrane by microorganisms in the sap. Because sap NATIONAL BOARD BULLETIN / FALL 2008 t27 FEATURE
Page 1 and 2: FROM SAP TO SYRUP the Art of Sugari
Page 3: BRAD GILLILAN OF LEADER EVAPORATOR,

to view a PDF of the - National Maple Syrup Festival

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?