Tapping maple trees is now completed in most areas of the province.  Weather forecasts for the upcoming week suggest good sap flow may occur early in the week and again by the coming weekend.  Maple producers can check for new sap flow each day where temperatures warm to around plus 5 °C higher, following freezing nights.  Where new sap flow is forecast, try to process previously collected sap from storage tanks as soon as possible to ensure storage for additional sap is available.   Maple producers can be caught off guard for sap storage where large sap flow events occur.   Try to clean sap storage tanks between sap runs to keep microbial growth out.

Wildlife management

Where vacuum tubing systems are in use, it is a good idea to check sap lines frequently during sap flows for leaks.   Squirrels, raccoons, chipmunks and skunks are becoming more active now as temperatures warm up and can sometimes cause chewing punctures on vacuum tubing.   Air leaks in vacuum tubing on wet lines or dedicated vacuum dry lines can reduce or prevent efficient sap collection.  Use of vacuum pressure gauges located at mainline junctions, with the ability of shutting off each branching mainline, can significantly speed up the job of finding air leaks in lateral tubing.   Contact a local Ministry of Natural Resources Wildlife Biologist if you want additional information on methods of managing wildlife in the sugar bush.

Hot packing maple syrup

Fresh syrup should be hot packed into glass bottles, metal or plastic containers for marketing.  Hot packing syrup at a temperature of 185 °C will ensure all spoilage organisms that may be present are killed and, to ensure food safety of maple products is achieved.  After filling each container and the lids are securely sealed, turn each container on its side or upside down for a few minutes to allow the hot syrup to sterilize the top air space area and inner lid of the container.   Hot packing syrup at temperatures hotter than 190 °C can lead to problems with syrup clarity after bottling is complete and containers have cooled.

Cooling too fast - The smallest syrup containers, small glass containers in particular, have experienced spoilage problems in the past due to the small volume of hot syrup cooling off too quickly and not properly sterilizing the inner surfaces.  Preheating small syrup containers with heated air or in an oven can help maintain hot temperatures long enough to properly sterilize maple syrup once sealed in small containers.   

Cooling too slowly - Stack burn occurs where freshly bottled syrup is allowed to stay hot and continue cooking for too long after packing into containers.  To prevent stack burn, spread out the sealed containers on a table in a cool room where the heat can dissipate quickly from the containers.   Some producers turn on a fan to remove heat faster from containers to prevent stack burn.  Large bulk storage containers should also be cooled as quickly as possible after sealing to prevent stack burn.  Once cooled, large bulk containers of maple syrup can be stored in a cool room, or in a refrigerated room that is sanitized for proper storage of food.

Only pack enough syrup from bulk storage to satisfy marketing needs for several weeks.  Syrup that sits for too long in small containers can darken in colour to a lower grade before sales are made.      

Understanding microorganisms

Maple syrup, like all food is a biological material that is derived or extracted from once living matter.  And like most food, raw maple sap and finished syrup is subject to microbial spoilage.  Many producers work hard to make high quality pure maple products that fetch premium returns.  Improving our understanding of how microorganisms can be controlled can help to maximize quality and ensure maple syrup remains pure and safe.  

What is food spoilage?  Spoilage refers to the unwanted loss of food quality as a result of specific biological, chemical and physical changes.   In maple syrup production, microorganisms such as yeast, moulds and bacteria are responsible for biological changes, such as fermentation in raw sap or in finished syrup leading to spoilage, such as surface mould.  These organisms can be found all around us in the natural environment.  It is important that producers and handlers of all foods learn to manage microorganisms in order to preserve food.

Microorganisms that are responsible for food spoilage are usually detectable by our senses (odour, off-flavour, odd texture and colour) but are not usually dangerous for consumption.  It is however, not wise to consume spoiled food.  Microorganisms that cause human illness, called pathogenic organisms, may not always be detectable by our senses when accidentally introduced into food.  Most of the time, these organisms travel through the air and can make contact with maple sap or syrup directly, or from contact with contaminated food surfaces due to unsanitary practices.  

Boiling sap is thermal processing.  An important advantage that maple syrup production has to ensure preservation is the thorough cooking process that it undergoes to remove water and create unique maple flavours and colour.  Cooking creates maple syrup but the bonus is a thermal heat treatment that microorganisms cannot survive, rendering it sterile.

The goal of thermal processing is to delay food perishability and inhibit food spoilage.  Thermal processing targets both spoilage and pathogenic microorganisms, destroying the organism and any spores (seeds).

Cooking requirements for maple syrup production is thorough at inhibiting microorganisms that may be present in raw sap.  Maple producers can inadvertently reintroduce microorganisms into finished sterile syrup by various methods such as, by adding raw sap to dilute finished syrup that has too high a sugar density, by inadequate reheating of finished syrup or containers during packing, by bulk storage in improperly sealed containers or in excessively warm storage facilities.    While packing finished syrup, always practice proper sanitary management of the production facility.

Wind management in the sugar bush

Sometimes cold wind blowing into a sugar bush can prevent sap flow on days that could otherwise be ideal for sap collection.  Sugar bushes that are sheltered by conifer windbreaks can warm up quicker by blocking cold wind and can allow sap collection on days where unsheltered sugar bushes may remain too cold and not permit sap to flow.  If cold wind is a problem, make some plans to plant conifer windbreaks this coming spring where you notice excessive amounts of cold wind in the woodlot.

This report has been prepared by Todd Leuty, Agroforestry Specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs.