slow or fast cooling

[Tapper705]

After canning or bottling syrup should it be cooled quickly or kept warm as long as possible. Most say to cool quickly but it seems to me to kill all spores etc. it would be better to cool slowly. Could someone please explain to me the reason to cool packaged syrup as quickly as possible, is it to create a vaccum seal quickly?

[RileySugarbush]

I believe it is to preserve the lightest grade. Holding at high temperatures can darken the syrup, know as stack burn.

From Dr Tim on the "other" forum:

Stack burn (http://www.sugarbush.info/forums/vbglossar.php?do=showentry&item=Stack+burn) can happen in any type of container. By itself, stack burn (http://www.sugarbush.info/forums/vbglossar.php?do=showentry&item=stack+burn) won't cause a change in flavor, but it can influence things that might. For example, if the inner containers heat up too much, you might get niter (http://www.sugarbush.info/forums/vbglossar.php?do=showentry&item=niter) forming and eventually get a niter (http://www.sugarbush.info/forums/vbglossar.php?do=showentry&item=niter) off-flavor.

Many (most) maple syrup cans are lined these days with a food-grade lacquer (that golden colored layer on top of the metal). Syrup packed in unlined metal containers may develop a metallic off-flavor after a period of time. It happens more frequently in syrup in an unlined can that was opened and then left in the container. The metal on the inside oxides faster and cause an off-flavor to develop.
__________________
Dr. Tim Perkins
UVM Proctor Maple Research Ctr
http://www.uvm.edu/~pmrc
Timothy.Perkins@uvm.edu