When does sap go bad?

[globetrotter]

My sap maybe close to going bad. It has white flecs starting to form, but still fairly clear. I've been freezing gallon sap cubes to keep it cold as possible. Smells a little buddy. Is it still worth boiling?
Thanks

[maplekid]

usaully it will smell a little bit sour. ive had lots go bad so i would know

[ibby458]

At the current demand for "black" syrup, it don't matter. I remarked to my buyer that I was going to pull the taps and dump out the yellow and slimy sap. He said "If you boil it, I'll buy it"

It stunk like hell, but I boiled it, he bought it and I got another $75 for it.