The lead content of most maple syrup is extremely low, even when made with lead containing equipment. However, the only way to know the lead content of your syrup is to have it tested. Maine testing services are available at the University of Maine. If tests show your syrup has lead levels within acceptable levels (below 250 ppb in Vermont), then your use of older equipment is satisfactory, provided you manage your equipment properly and retest periodically. Samples sent for lead testing should be representative of most of your syrup. Try to sample syrup from several syrup batches and try to sample syrup made at the beginning and end of a sap run. Sample only syrup that has received the final filtering. Collect samples in a clean glass or plastic container and combine into one lot. Send the required amount, usually only a few ounces, to the lab of your choice.
Lead does not come from trees. Sap collected using lead-free plastic materials has virtually no lead in it. Sap collecting and syrup making materials that contain lead include: 50/50 solder, used before 1995 for evaporators, tanks and some buckets (Leader Evaporator switched to lead-free solder in 1991); galvanized equipment made before 1994; most brass and bronze; and terneplate, an alloy used for some older equipment. Sugar sand concentrates any lead in the sap as it is formed so it should also be treated as lead containing. Roadside dust and dirt may also contain lead. In tests of several models, all older metal spouts added lead to maple sap. Very old spouts may be made of terneplate and will leach large amounts of lead into the sap. Lead-free metal spouts are now available. Not all buckets are equal when it comes to lead. In tests, Wheeling buckets added the least amount of lead, while old "tin" buckets added the most. Some old buckets have shinier terneplate bottoms; beware of these. Lead containing buckets begin to leach lead into sap within the first few hours, and continue to add lead to sap as long as it is in contact with metal surfaces. Storage of sap in buckets for several days, which may occur when sap runs slowly, can result in very high sap lead concentrations. Galvanized and lead-soldered tanks also add some lead to sap, although usually less than buckets, because their surface-to-volume ratio is smaller. In an evaporator, a lead-soldered back pan adds more lead than a lead-soldered front pan, due to the many solder seams. The lead content of partially made syrup often decreases in the front pan, as lead is precipitating and sticking to the pan in the form of sugar sand. After the evaporator is shut down, lead will continue to accumulate in the partially boiled syrup from lead solder. Draining the front pan into buckets and adding the syrup again once boiling resumes, reduced lead accumulation. Cleaning the front pan with water may remove some of the sugar sand (source of lead) but also re-expose lead solder (source of lead). Water cleaning had little effect on syrup lead concentration. Frequently cleaning a lead-soldered pan with acid will likely result in higher syrup lead content. Sugar sand may contain extremely high amounts of lead, depending on the concentrations of lead in the evaporator. Good filtering is essential for keeping lead out of syrup. In tests, cone filters, were as effective as filter presses in removing lead. A large percentage of lead in syrup is in a dissolved form, however, which is not filterable. Bronze used in the manufacture of gear pumps usually contains lead, and these pumps can add lead to sap and syrup. Unnecessary pumping, particularly of sap, should be avoided. Other pump models are available which contain little or no lead. Old milk cans frequently contain terneplate, an alloy with a high lead content, and should never be used for syrup filtering or storage. Syrup kept in older, heavy galvanized barrels have a much higher lead content after 8 months of storage. Newer galvanized barrels do not add appreciable lead in the same amount of time. Condensed from from Wilmot, T.R. and T.D. Perkins. 2000. Keeping Lead Out of Maple Syrup: A Guide to the Use of Sap Collecting and Syrup Making Equipment. Proctor Maple Research Center, University of Vermont. |
