My book says if it gets moldy on top...scoop it off with a spoon and reboil and it's still good.
It says, they use 1 lb and 2 lb coffee cans with plastic lids, freezer tape lids shut, the syrup is so hot it's sterile already, they slosh it around-sterilizing lids, & they know seal is good when plastic lid drawn down tight in a concave shape as the small amount of air in can cools and contracts.
also says you can use mason jars as long as rubber seals are good.
and store in cool dry place...like you would canned veggies.
they never had spoilage...but they say they keep it in thier freezer.
sap is spoiled when it has a unclear, slightly milky look...boiled down it will make a dark syrup.
keep sap in a cool shaded area...while holding to reduce spoilage.
"The opportunity in frozen sap is the opportunity to reduce your boiling time, and if you come out some morning and find a good layer of sap ice in your holding tank, you should take advantage of it. the ice actually is very spongy and is made up of frozen crystals of wather that have separated out fromthe sugar, trapping the more sugary sap within the ice, something like a honeycomb. one of the ways the indians andearly settlers used to make syrup was by suxxessive freezing of the sap, each time throwing away the ice, until the remaining liquid was usable as syrup. the problem with this methiod is that some suragary sap isa always thrown out with the ice, so that this method is less iffeiceint that boiling. in any event, if you do find a couple of inces of ice in your holding tank, prop it up over your holding tank in some way so it drains well back into the tank, then pitch it out. you'll have saved yourself some boiling time."
that's all my book says.
me,
g