When they make Maple syrup they boil off the water in order to concentrate the
sugars in the sap. The question is: Could you save money by setting up a vacuum
to lower the boiling point? Would seem that with a lot less heat you could just
vacuum the steam away. Would it work and would it be worth doing?

On Tue, 19 Jul 2005 11:57:48 -0400, Sam Clayton wrote:
When they make Maple syrup they boil off the water in order to concentrate the
sugars in the sap. The question is: Could you save money by setting up a vacuum
to lower the boiling point?

Until the water turns into steam and blows your volumetric gains out the
window, I suppose it would.

In article , Sam Clayton says...

When they make Maple syrup they boil off the water in order to concentrate the
sugars in the sap. The question is: Could you save money by setting up a vacuum
to lower the boiling point? Would seem that with a lot less heat you could just
vacuum the steam away. Would it work and would it be worth doing?

I recall seeing the distillation units on a ww2 submarine. They
were electrically heated stills with large roots blowers on top
to pull vaccum. I guess at some point you win because it costs
less power to run the blowers than it does to provide heat input.

The widget under the gray motor on top of the still is the roots blower:

http://www.njnm.com/subtour/images/distill2.jpg

Jim


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Sam Clayton wrote:
When they make Maple syrup they boil off the water in order to concentrate the
sugars in the sap. The question is: Could you save money by setting up a vacuum
to lower the boiling point? Would seem that with a lot less heat you could just
vacuum the steam away. Would it work and would it be worth doing?

I can almost guarantee commercial processors do it this way. Condensed
milk is made that way, along with a lot of other things.

Jon

Dave Hinz wrote:

On Tue, 19 Jul 2005 11:57:48 -0400, Sam Clayton wrote:
When they make Maple syrup they boil off the water in order to concentrate the
sugars in the sap. The question is: Could you save money by setting up a vacuum
to lower the boiling point?

Until the water turns into steam

Yes that's what you do get when you boil off the water, no dispute about that!

and blows your volumetric gains out the
window, I suppose it would.

Yes I think it could too, but the question is whether it would work well enough to be
of any value.

Jon Elson wrote:

Sam Clayton wrote:
When they make Maple syrup they boil off the water in order to concentrate the
sugars in the sap. The question is: Could you save money by setting up a vacuum
to lower the boiling point? Would seem that with a lot less heat you could just
vacuum the steam away. Would it work and would it be worth doing?

I can almost guarantee commercial processors do it this way. Condensed
milk is made that way, along with a lot of other things.

Jon

Thanks Jon

I would think so too, but in all the documentaries of the maple syrup industry in
Quebec that I've see, I have never seen anything but enormous open top boilers at
work.

I've helped setup commercial "sap" units and "NO" they are not done this
way. Typically you start with reverse Osmosis and good producers will use
air under the sap to keep it from caramelizing on the bottom of the
evaporator. It would be an interesting theory to try though. Does anyone
have any idea how much vacuum you would need to apply at sea level to boil
water at 50 C


"Sam Clayton" wrote in message
...
When they make Maple syrup they boil off the water in order to concentrate
the
sugars in the sap. The question is: Could you save money by setting up a
vacuum
to lower the boiling point? Would seem that with a lot less heat you could
just
vacuum the steam away. Would it work and would it be worth doing?

jim rozen wrote:

In article , Sam Clayton says...

When they make Maple syrup they boil off the water in order to concentrate the
sugars in the sap. The question is: Could you save money by setting up a vacuum
to lower the boiling point? Would seem that with a lot less heat you could just
vacuum the steam away. Would it work and would it be worth doing?

I recall seeing the distillation units on a ww2 submarine. They
were electrically heated stills with large roots blowers on top
to pull vaccum. I guess at some point you win because it costs
less power to run the blowers than it does to provide heat input.

The widget under the gray motor on top of the still is the roots blower:

http://www.njnm.com/subtour/images/distill2.jpg

Jim

Good example !!! Thanks.

On Tue, 19 Jul 2005 13:11:14 -0400, Sam Clayton wrote:


Dave Hinz wrote:

Until the water turns into steam

Yes that's what you do get when you boil off the water, no dispute about that!

Well, makes your vacuum pump have a whole lot more volume to move.

and blows your volumetric gains out the
window, I suppose it would.

Yes I think it could too, but the question is whether it would work well enough to be
of any value.

At some scale, perhaps...shouldn't be too bad of a thermodynamic
calculation, the tricky part would be finding out how sap behaves in
that situation, and how that changes as it becomes more like syrup.

That's a good question. It turns out to be easy to give an answer to
someone who's studied a little Statistical Mechanics, but I'll try to
give an answer that doesn't assume that sort of background.
"Sam Clayton" wrote in message
...
| When they make Maple syrup they boil off the water in order to
concentrate the
| sugars in the sap. The question is: Could you save money by setting
up a vacuum
| to lower the boiling point?
Maybe, but the added complexity of the system probly negate any
advantage. The normal process uses multiple vats, heated to
progressivly higher temperatures to deal with the higher bioling point
of the syrup. Why? Sugar can easily dissolve in liquid water. However,
taking the solute (sugar) out of the water and putting it in the gas
phase (air) requires a lot of energy. At temperatures around the water
boiling point, these solutes stay in the liquid.
Now the total pressure in the syrup and the air at the boundary are
the same, otherwise one would push the other into a smaller space.
Part of the pressure in the syrup comes from the solutes, not the
water. So the pressure due to the water alone is reduced compared to
that of pure water at the same temperature. The vapor pressure, that
is, the pressure of water vapor that would stay in equilibrium with
the syrup, is reduced by the same amount because of the solutes.
Syrup boils when the vapor pressure of the syrup gets to be as big as
the pressure of the atmosphere. At that point, vapor bubbles in the
syrup can grow. You have to heat the syrup with solutes up more to get
the vapor pressure in it to equal the atmospheric pressure, so it has
a higher boiling point.

Well of course you say that's my whole point. And sure enough it is.
But syrup production isn't a batch process, it's a continuous process,
controled by temperature alone, no other instrumentation is required.
Even the reverse osmosis used today to pre-consentrate the sap before
it enters the vats requires little instrumentation.

However, it you seal the process, as would be required to produce a
vacumm, you will now need instrumentation and process control
equipment which will increase your cast of production signiticantly.

| vacuum the steam away. Would it work and would it be worth doing?
|

Sam Clayton wrote:

When they make Maple syrup they boil off the water in order to concentrate the
sugars in the sap. The question is: Could you save money by setting up a vacuum
to lower the boiling point? Would seem that with a lot less heat you could just
vacuum the steam away. Would it work and would it be worth doing?



This is done with tomato paste and similar products that have a tendency
to burn or discolor/disflavor as temperatures rise above boiling when
the sugars and pulp concentrate. It doesn't really save on energy, just
improves product quality.

As someone said, evaporated milk is done in a similar manner also. I'm
not sure that there would be any benefit to doing maple syrup this way
on a small or even commercial scale.

There is also a process of spray drying in a vacuum to extract the
powder form of the product which is then often re-hydrated with
controlled amounts of water to improve consistency. I believe that
there are products similar to maple syrup which are done this way as it
tends to be fast and cheap to use as a continuous process rather than
"batch" processing.

Koz

You still have to supply the heat of vaporization to get the water to
evaporate.

"Sam Clayton" wrote in message
...
When they make Maple syrup they boil off the water in order to concentrate
the
sugars in the sap. The question is: Could you save money by setting up a
vacuum
to lower the boiling point? Would seem that with a lot less heat you could
just
vacuum the steam away. Would it work and would it be worth doing?

Sam Clayton wrote:
When they make Maple syrup they boil off the water in order to concentrate the
sugars in the sap. The question is: Could you save money by setting up a vacuum
to lower the boiling point? Would seem that with a lot less heat you could just
vacuum the steam away. Would it work and would it be worth doing?

They say that you can expect to get 5 cords (real cords, not face cords)
per acre from most forest/wood lots in perpetuity. This assumes only
taking the dead and/or down stuff and keeping things nice. My
experience has me believing that. So you might as well use it to boil
the sap.

When we were in Kingston, Ontario we gathered enough sap for own use. I
built a proper fire place out of doors for the boiling. Do _*NOT*_ do
it in the house - the water vapour will destroy your ceilings unless
they're finished in stainless steel (metalworking content).

Ted

Ted Edwards wrote:
Sam Clayton wrote:
When they make Maple syrup they boil off the water in order to
concentrate the sugars in the sap. The question is: Could you save
money by setting up a vacuum to lower the boiling point? Would seem
that with a lot less heat you could just vacuum the steam away.
Would it work and would it be worth doing?

They say that you can expect to get 5 cords (real cords, not face
cords) per acre from most forest/wood lots in perpetuity. This assumes
only
taking the dead and/or down stuff and keeping things nice. My
experience has me believing that. So you might as well use it to boil
the sap.

When we were in Kingston, Ontario we gathered enough sap for own use.
I built a proper fire place out of doors for the boiling. Do _*NOT*_ do
it in the house - the water vapour will destroy your ceilings unless
they're finished in stainless steel (metalworking content).

Various experiments have been done in the area of maple sap concentration
but the bottom line is that the open boiler is partially responsible for the
rich flavour of the syrup. Vacuun concentrators yield an unsaleable product.

Regards.
Ken.

Sam Clayton wrote:

When they make Maple syrup they boil off the water in order to concentrate the
sugars in the sap. The question is: Could you save money by setting up a vacuum
to lower the boiling point? Would seem that with a lot less heat you could just
vacuum the steam away. Would it work and would it be worth doing?


It is done that way, but for cane and beet sugars. It was invented by
the son of slave to create a safer work environment for slaves:

http://www.africanamericans.com/NorbertRillieux.htm

The process not only uses vacuum to boil evaporate the stuff, but it
uses the heat released by condensing spent vapor to heat the syrup.

Apparantly it's not used for maple sugar, though:
http://www.edsanders.com/lan028.htm.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

In article , Ken Davey says...

Various experiments have been done in the area of maple sap concentration
but the bottom line is that the open boiler is partially responsible for the
rich flavour of the syrup. Vacuun concentrators yield an unsaleable product.

Translation: 'all kinds of other stuff winds up in the vat while it's
cooking down. It makes it taste like the real deal, but you don't
want to know what the chef's secret seasoning really is!'

Jim


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please reply to:
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"HotRod" wrote:
Does anyone have any idea how much vacuum you would
need to apply at sea level to boil water at 50 C?

This is given by the vapor pressure of water at 50C, which turns out to be
92.5 mm Hg.

Jon