North American Maple Syrup Producers Manual, Bulletin 856-96

Ohio State University Extension Bulletin

North American Maple Syrup Producers Manual
Bulletin 856

Chapter 6 · Maple Sap Production - Tapping, Collection and Storage

Ultra-Violet Lights and Sap Filters

The importance of minimizing microorganism contamination in producing quality maple products has been repeatedly emphasized. Two pieces of equipment being used by some maple producers to minimize microorganism contamination of sap are ultraviolet lights and small pore filters.

Passing sap through an in-line ultraviolet light unit when the sap is transferred from the collecting tank into the sap storage tank has been shown by research to reduce the amount of living, multiplying microorganisms, particularly bacteria, in the stored sap (Figure 6.30). In many instances, this has resulted in longer sap storage times without a reduction in the grade of syrup produced, and in the production of higher-quality syrup, particularly late in the season when microorganism contamination is at its highest. Commercial in-line ultraviolet light units for use in treating maple sap are available through maple equipment dealers. Extreme caution is necessary when using ultraviolet light as it can cause permanent eye damage. Ultraviolet lights suspended over sap storage tanks are extremely dangerous to the naked eye.

Figure 6.30. An in-line ultraviolet light for treating sap. Figure 6.31. A cartridge filter (a - left) and diatomaceous earth filter (b - right) used to remove microorganisms and other contaminants from sap.

Passing sap through a small-pore filtering system as the sap is transferred into the storage tank can also markedly reduce the microorganism content of the sap (Figure 6.31). Microorganisms in sap range in size from hundreds of microns to less than a micron, and multiply very rapidly. Commercial sap filters, as well as other types of liquid food filters, can be used to filter microorganisms from sap, potentially increasing its storage life and the quality of syrup produced. In general, the finer the filter the more effective the filtering process. Usually when very fine filtration is desired, a series of filters down to around 0.5 microns is used to perform the filtering process in steps.

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Figure 6.30. An in-line ultraviolet light for treating sap.	Figure 6.31. A cartridge filter (a - left) and diatomaceous earth filter (b - right) used to remove microorganisms and other contaminants from sap.