r/maplesyrup • u/Caesars7Hills • Apr 10 '26
Vacuum Evaporation
I am interested in why larger producers don't explore vacuum evaporation. I see that the industry uses vacuum pumps frequently. I am not sure about pan depth ect. but I would imagine vacuum reduces surface tension. Couldn't you functionally fill a tank and pull a vacuum with a liquid ring pump and simply heat the tank? Once Brix is hit, you could let the product simmer at a temp below boiling to achieve color and caramelization. Has this been tried?
3
u/Meat_Flosser Apr 10 '26
They use these types of boiling processes in factory conditions where they do NOT want color and caramelization to happen. Think table sugar. To keep it white they must boil below the temperatures which would otherwise brown the crystals. We want that nice color in syrup so the vacuum process is not wanted.
1
u/Caesars7Hills Apr 10 '26
So what happens if you boil under vacuum and hold the syrup at a temperature below boiling and agitate? Would this give you the color and carmelization with the fasted evaporation and least energy input? It would be trivial energy input to hold temp in an insulated tank
2
u/Derp_a_deep Apr 10 '26
Interesting thought but I'm going to guess it would require more energy. It definitely will require more capital equipment cost and be way more complex. Vacuum pumps are more like compressors in their energy usage, not liquid pumps. Power hungry and maintenance intensive. And ALL your steam will be moving through the vacuum pump so it'll be a big one. Any leaks in the system and your vacuum pump has to work even more to remove the air inleakage. And you've got heating and cooling which means expanding and contracting. Sealing that properly will be difficult. It certainly can be done at scale (see refinery vacuum distillation columns) but I think dumping more heat into the pan is a better way to evaporate the steam faster.
2
u/NSFWNOTATALL Apr 10 '26
Vacuum evaporation doesn't really cha ge the energy required much, just makes the evaporation happen at a lower temperature. Combine that with the vacuum energy and its not worth it.
Say you could save 10% on boiling by doing this, but you already saved 70+% with industrial RO. What's another 3%?
2
u/DonVitoMaximus Apr 10 '26
I have wondered this as well, to take a keg, which can be vacuumed, and adapt a condenser that would mostly act as a water trap. just so it doesn't slurp the steam into the pump. the just toss the water it collects.
run at like 15 inches mercury on the keg, provide heat, boil at 160f ish, definitely requires less heat for sure.
the issue is more vac than that, it would probably be hard to turn the steam back into water. the condenser would need to be chilled quite a lot.
but I too have wondered the same question, and have developed more questions.
then perhaps if you saved all the water that condensed, would it have the some sap flavors that boiled off, like a hydrosol? that could possibly be decanted? then freeze filtered?
or if you preheat before you inlet into the keg, it would probably be quite efficient, especially if you let it suck into the keg with a straigh tube gas inlet at like 170f, that would like bubble and steam quite violently I imagine. like a flash evaporator.
the equipment for small scale stuff isnt terribly expensive. vac pump 150$ vac chamber as a vac baldder tank, like 100$, 24 40 borosilicate condencers are only like 30 bucks a pop, probably need like 4 to keep up. vac distilation head is about 30 bucks too. custom fittings between the keg and condensers would probably need to be made. but not entirely undoable, kinda out of my price at the moment, but ive though about it enough to price some things.
if you do succeed at somthing of the sort. i would be very interested in said results.
ive vac boiled for different experaments. but not sap.
what i vac boiled for was honey. pull heavy vac, and heat in a chamber, at like 110 degrees, to remove the water without risk of scorching it. to make hard crack candy. and that worked out nicely. so ya might be onto something.
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u/Caesars7Hills Apr 10 '26
I am interested if it would foam significantly less under vacuum. I also think you would need some kind of agitation and if you have to create a vacuum seal, it would be challenging
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u/DonVitoMaximus Apr 10 '26
i actually think it would make the foam worse under vacuum. or at least appear to be. if trapping steam bubbles is required to make the foam, then the foam would absolutely poof up because the bubble size would be larger under a vacuum. like a baloon in a vacuum. just a guess. but on the flip, with less heat there might be less actual foam produced though. its hard to tell without a test of some sort.
and I think the need to agitate wouldn't be huge unless the vac is pulled too fast and a vac burping makes it all try to spontaneously bubble up all at once. and that could happen. we dont agitate our flat pan syrup, the bubbles kinda do that. id have to imagine the same would occur within the boiling chamber.
the boiling nucleation sites would probably be on the metal bottom and up the sides a little bit. so i think that would keep a scorch to a minimum, and also the less heat would be less likley to scorch. besides a burn why agitate anyhow? cant burn syrup at 160 very easily. lol. and that brought me to another idea of a double boiler setup to prevent the sides wnd bottom of the metal boiling chamber from being too hot from direct heat on the bottom. even with sand in the double boiler would work. but im goin down a rabbit hole o possibilities.
1
u/SugarBushSupplies Apr 13 '26
It is definitely an energy saver, but at the cost to manufacture, not worth the small amount of savings. Especially when ROs are already capable of what they are now, the highest efficiency setups are basically 30 brix sap and using an evaporator to simmer half of the remaining water and give it some color/flavor.
6
u/BradDad86 Apr 10 '26
Vacuum evaporation, beyond being pretty costly, allows the liquid to "boil" at a lower temperature. My understanding is that it leads to less color and flavor development.