thermal vacuum wort "boil?"

[lemthree]

I notice japanese slow-cookers (http://www.google.com/products/catalog?q=tiger+thermal+cooker&cid=17765751767885645299&os=sellers ) that use a thermal vacuum to keep boiled water hot for several hours.

How bad would it be to "boil" wort for an hour by keeping it a steady, near-boiling temp that isn't quite a boil?

Yes, this is lazy and it would be a roiling boil. Also wouldn't heat up the kitchen or use much gas.

 

[Navy_Chief]

I don't think that a vacuum boosted boil will do as much to sanitize the wort and remove SMS (DMS precursor) from the wort. There are a lot of complex chemical reactions that are taking place during the boil that boiling at a lower temperature will change.

 

[Lost]

Why not go electric then? Heat sticks are pretty cheap to make and use. It is much cheaper than gas.

You need a good boil to cook off the dms and, if you're doing all grain, to concentrate the wort a bit. I don't think a near boil would accomplish that. You could try it but I'd rather spend the cash on some brewing gadgets that I know would work.

 

[SankePankey]

This is what some larger breweries do. Rogue for instance. It's to save power and save time. I think they said they do a 45 min boil.

 

[JKoravos]

That would cause some issues. A big part of the boil is driving off volatile compounds that don't taste or smell very good. You need a rolling, uncovered boil to achieve that.

 

[lemthree]

Folks, this has been a very helpful thread--thanks. I never new about the DMS, which may explain some off flavors I have had from keeping the lid on.

My ultimate goal was (like many before me) to design a solar brewer. So I looked for a pot that would not lose any heat. Now I understand the importance of an open boil, which will necessarily lose lots of heat.

But this has also lead me on my search for the harsh/skunky flavor a few of my batches have had. Mostly, I get a very good result. But lately a few IPAs have turned out a bit skunky. That obviously could be light (I didn't realize until today that light can damage the wort IN A VERY SHORT TIME). Or it could be contamination (using the same buckets for several years, although I always clean and sanitize them). Or it could be DMS.

Aside from cost, why use electric brewing? As a bit of an enviro/energy nut, I would note that, even if the electricity is cheaper, it probably uses much more fuel due to efficiency losses at the power plant and on the distribution system.

 

[mredge73]

Check this out:
http://www.solarhomebrew.com/

Fresnel Lenses are available on ebay for pretty cheap, looks like the way to go.

 

[Bithead]

This LHBS is not far from me but I haven't been there yet. Check his videos.
http://www.solarhomebrew.com/

 

[seabass07]

If it is truly vacuum assisted, then the steam is being removed. You shouldn't have to worry about DMS since anything boiling off would be removed by the vacuum.

 

[Catt22]

Folks, this has been a very helpful thread--thanks. I never new about the DMS, which may explain some off flavors I have had from keeping the lid on.

My ultimate goal was (like many before me) to design a solar brewer. So I looked for a pot that would not lose any heat. Now I understand the importance of an open boil, which will necessarily lose lots of heat.

But this has also lead me on my search for the harsh/skunky flavor a few of my batches have had. Mostly, I get a very good result. But lately a few IPAs have turned out a bit skunky. That obviously could be light (I didn't realize until today that light can damage the wort IN A VERY SHORT TIME). Or it could be contamination (using the same buckets for several years, although I always clean and sanitize them). Or it could be DMS.

Aside from cost, why use electric brewing? As a bit of an enviro/energy nut, I would note that, even if the electricity is cheaper, it probably uses much more fuel due to efficiency losses at the power plant and on the distribution system.

The skunk term regarding beer is ususally a result of UV light exposure. A chemist once told me that the skunking phenomenon was a reaction between the hops and the UV, but what he also said, that I have never heard before, was that the presence of alcohol was required for the reaction to occur. At least that's what I understood him as saying. I was concerned about brewing outdoors where the boiling wort w/hops might get skunked from direct sun exposure and I was thinking about using a canopy to shade the kettle. That's when he said it only happens in the presence of alcohol, so not to worry about it. I don't know is this is actually true or not.

Now then, DMS problems manifest as a cooked corn or general cooked vegetable off flavor. It should be relatively easy to differentiate between the two, but I suppose you could have both problems in the same beer under the right circumstances. The DMS is easy to avoid with a vigorous uncovered boil kettle and the skunking by avoiding UV light exposure. You may be mistaking skunking for oxidation problems. The oxidation defect would have a wet cardboard type of flavor. It's pretty distinct flavor and fairly easy to recognize. There are other possible off flavor causing defects and it's not all that unusual to encounter more than one in the same beer. I've had very good luck avoiding all of these with the exception of a few batches early on in the hobby. Once I thought I had an oxidation problem but have since traced it to the plate filter I tried using. I think that I did not flush the filter sufficiently and it was a cardboard taste contributed by the filter pad itself and not an actual oxidation issue. I never used the filter again, so i don't know for sure if that was the problem, but it's my latest theory. I may give it another go sometime, but in no hurry to do so really.

Electric brewing is inherently more efficient when done with a heating element position directly in the water/wort. IIRC, nearly 100% of the heat generated is transferred to the liquid. With gas, much of the heat escapes around the side of the kettle. It's a huge difference in efficiency. The power transmission losses for electricity are probably much less than you think they are. I checked it out one time and I was very surprised at how little energy is lost through transmission. I was expecting something like 25%, but it was nowhere near that IIRC. OTOH, most of the power plants are burning coal and there's really no clean way to do that. It's also a non-renewable resource (unless you have a few hundred million years to spare). It's the same for the dinosaur gasses.

I've often thought about solar brewing, but abandoned the concept mostly because it would be tricky to control temperatures with speed and precision and if trying to use solar for the boil you would need a big bad parabolic reflector or lens of some kind. Lots of photovoltaic cells could provide juice, but it would take a whole lot of them to generate a couple of kilowatts. Solar reliability would be dicey and dependent on the weather, time of day, time of year etc. In a post apocalyptic world the alternatives would likely be very limited, but we would automatically return to fire. A bigger problem would be acquiring the ingredients. I bet any malt available would be consumed as a porridge type thing. Fun stuff to think about at times and ya never know when some wild idea might actually catch fire and change the world. It has happened before. What if...?

 

[lemthree]

I, too worried about the UV skunking the wort during boil (I used a fresnel yesterday, but couldn't get it up to boil). So thanks for putting that to rest.

Oxidation is a potential culprit--I just switched to a glass carboy from the buckets, to see if that does it.

I have seen one fresnel brew on the web (using glass-front refrigerator to hold in heat): that looks pretty cumbersome, so I am trying to develop a different design. My understanding is that solar hot water heaters can deliver 180 degree water--but the pipes may give it an off taste, so I am going to look into a solar hot water heater that uses stainless pipes.

The big loss in electricity is that 2/3ds of the fuel at the power plant (varies a little with the type of plant and fuel) is wasted as heat. By contrast, only 10% is lost in transport of natural gas to your burner. The 1/3 of energy left in generated electricity then looses about 6-8% in line losses ON AVERAGE. Of course, the average masks large variations: at peak times line losses may be much higher. So most of the fuel in the electricity has been wasted long before it gets to your house.

 

[SankePankey]

You can always use a heat exchanger in conjunction too if the hot water itself isn't potable. Beats making "everything" stainless and food grade just for that.

 

[JKoravos]

If it is truly vacuum assisted, then the steam is being removed. You shouldn't have to worry about DMS since anything boiling off would be removed by the vacuum.

it's just a thermos big enough to fit a pot into.

 

[lemthree]

Right, JKoravos, the japanese slow-cookers are just a large thermos. I suppose I could revert back to college physics and try to figure out how much heat is lost through the sides (versus the top and bottom) of the pot. Then, an electric heating element inside a thermos -type pot might be very efficient.

BTW, I became interested due to the New Belgium study on CO2 impacts of brewing. The largest impact (about half) is the refrigerator at the grocery store, due to so many being open refrigerators. Malting barley is second. Activities at the brewery are only 4% of the lifecycle carbon impact.

 

[audger]

you would need to figure out the vapor pressure of DMS and other chemicals and see if any would be out-gassing much more then normal. who knows; maybe alpha acids in hops vaporize at just under atmospheric pressure. if so- when you pulled the vacuum, you might just suck off some/all of your hops oils and end up with a completely different beer...?