Holding concentrate in a working bulk tank

[Mean_Oscar]

How long will frozen sap and concentrate (0 to 10 F) last?

[Bucket Head]

As Dr. Tim mentioned, that time will vary, depending on the initial sap quality. I once held 12% concentrate for a week and it made great syrup. However, it was early season sap and was crystal clear. I didn't want to keep it that long, but it was bitter cold for a week and I didn't get any more sap. Late season sap probably would have been a different story. But just having the ability to hold sap and/or concentrate, for whatever reason(s), lowers the sugaring season stress level significantly!

Steve

[DrTimPerkins]

It's a difficult thing to predict given the number of factors. The main one, which isn't easy for sugarmakers to judge, is the level of microbes in the sap. The real problem is that once they get started, growth is exponential, so sap or concentrate can be just fine one day (or one week), but will have gone bad the next day.

[Mean_Oscar]

I need to clarify that question. These are 2 gallon and 5 gallon size batches in commercial freezers. I always figured frozen (0 F to 10 F) would keep indefinitely like orange juice concentrate (if it did not dehydrate and all of ours has lids). Or steaks or vegetables in a freezer. I have kept sorghum juice (20 Brix) frozen in a plastic bucket for several months and it was fine.

So the question better stated would be: would, say 6%, maple sap concentrate deteriorate in a month frozen brick hard? If there is a problem it may be the 2 1/2 days freezing and 2 1/2 days thawing when it is at the ice and water equilibrium of 32 F.

[Mean_Oscar]

Aside from experience, how do you decide if concentrate is "bad"? Appearance / opacity? Smell? Taste? pH? Brix decrease?