Recently I was reminded of the old saying, “Treat sap like milk.”
That begs the question - how do you treat milk?
I did not grow up on a dairy farm, but my dad did. So I've heard a number of stories about dairy farming but have no experience of my own. Treat sap like milk is an old saying. But how old? The rules in my dad's youth were keep it cool, process it quickly, and keep the barn cats out of it. That sounds like good advice.
Starting in the 1950s, changes in food safety regulations forced farmers to switch from milk cans to double walled refrigerated stainless steel tanks. Not all farmers could afford to upgrade. On the wall in my dad's house is a framed copy of the auction poster from when his dad sold off the dairy herd in 1957.
Did “Treat sap like milk” come from and age when syrup was collected in buckets and dumped into a tank on a sled drawn through the snow by horses? Or is it as new as tubing systems with vacuum and reverse osmosis?
Are we asking the right questions?
One thing sugarmakers have learned relatively recently is that the fermentation of sap is responsible for a lot of its flavor. We used to say that as the temperature rose though the season, the color and flavor of the maple syrup change - which is true - but there is a missing step.
Warmer temperature does not directly change sap -- temperature changes the rate of fermentation of the sap. Fermentation is necessary for good flavor in syrup. If we treat sap like milk in refrigerated tanks, we are slowing the rate of fermentation.
Is that good? It depends. We make a Golden (formerly know in Vermont as Fancy) that is so clear it looks almost like water. It can be lighter than the sample on the left. A 22% grade and a collection system that runs into a covered tank on a concrete slab makes for very fresh and unfermented sap.
Making Fancy/golden is like falling off a log. The flavor is pure and very delicate. More flavor would be make it better. So yeah, this year we are going to try to turn up the fermentation on sap that would otherwise make golden. There was a time we made 50% golden and we could not make dark amber. We kept getting asked for dark (grade B) but could not do it with our collection system and sap storage. So we set up some poly aging tanks in the sun to try to make dark to make our customers happy.
Using a glucose meter to measure invert sugar, we could get a sense of when it was going to make dark. It worked on a test basis. But one time it got away from us and we had to dump it and wash the tank thoroughly. It had become ropey syrup. Too much fermentation.
If I remember the research right, the sap gets warm and the microbes that ferment the sap not only go crazy converting sucrose to glucose and fructose but they multiply. Under the right conditions they multiply like crazy. The disgusting ropey slime is all the proteins from the billions of microbes in the sap chaining together. Way too much fermentation.
Keeping it colder and dialing back the fermentation would be a win. There is a twist. Perhaps, if I have the facts right. The microbes responsible for ropey syrup are anaerobic, meaning they flourish when there is no dissolved oxygen left in the sap.
What if you increase the dissolved oxygen? That's a good question presented in research by Aaron Wightman at Cornell. If you let sap sit and it's warm enough for the microbes to get busy, boil as soon as you can. If it gets ropey, throw it all out, even what's in your evaporator. Because of the proteins, the ropey sap has a lower boiling point. That makes it almost certain to scorch and warp your pans.
If you can see warm weather coming and you know you can't boil, work week on your day job, etc., cool the sap down fast and hard to stop fermentation. Maybe sell it to someone who can boil it. But do it quickly. There is nothing you can do that will hurt more than warping your pans. Hopefully you can see that there is some wiggle room in interpreting “Treat sap like milk.” This isn't an exact science so take baby steps. When in doubt, keep it cool, process it soon, and keep the squirrels out.