Yes and No,
The evaporation is controlled by the heat flow into that evaporator.
(How does that evaporator look like? Could You post/link a picture?)
So foam is not the control, but the limiting factor, because You have
to reduce heat flow to avoid the foam spilling over.
To "fight" that foam, there are several possibilities:
Kind of stirrer/cam agitating above the surface of liquid.
Whether this is helpful, You know better than me, just
try the foams reaction to some agitation by a stick/paddle.
Coating the upper part of the evaporator and that foam breakers
with some hydrophobic plastic (eg PTFE) might help.
Big diameter flat evaporation vessel with ample space above liquid.
Antifoam agents: more theoretically, because those might leave
some unpleasant smell/taste in the syrup. You needed a food
grade defoamer, I don't know whether such are available.
Some hints to defoaming: most defoamers are some hydrophobic
substances like petroleum (that used for lamps) or fat.
This fatty substances will disperse in the foaming liquid as
fine droplets, which act as rupture initiation points on the foam
If the syrup was for my own use only, I'd try to add some paraffine wax
(food grade) for a trial. (one gram on 100 ltr of syrup, not more!)
The wax will separate after cooling down, (and swim on top I assume?).
Just try that in a pan with a small amount of syrup. The critical
factor is this removal, maybe the paraffin remains dispersed as tiny
droplets in the syrup. Removal by adsorption filtration is possible, but
that is more messy/lossy than slow enough evaporation.
Another point: some of the taste of maple syrup comes from heating
for some time (caramel reaction). In case You reduce this time by
reduced foaming, You might get a very light (color) syrup missing the
foam is not just a question of surface tension, think of water, which has
the highest surface tension of all liquids (exept molten metals).
Foaming is a very complicated process, viscosity, not too high
surface tension are the main "incredients".
Thank You for the picture! A evaporator more flat than this one
is not possible, I think.
In chemical technology there are a number of machines which were developed
to evaporate/concentrate viscous and foamy liquids. But those are big machines,
not for such a small scale business.