Pure Maine maple syrup contains no preservatives and should be refrigerated or kept in a cool dry place after the seal is broken. Properly prepared maple syrup will not freeze, and the freezer makes an ideal storage place. Or it may be heated to 180 degrees and canned in sterilized jars. Process pints in boiling water for 10 minutes. If syrup ferments, it can be restored to full flavor by bringing it just to the boiling point without stirring. Let it simmer for 2 or 3 minutes, then turn off the heat and let it cool to room temperature. Skim all matter that rises to the surface, boil briefly once more and store as above.