Any downside to a low boil off rate?

[InspectorJon]

I have a 7 gallon kettle. It takes a lot of energy to get the contents up to boiling temperature. Obviously more energy with a larger volume of liquid. Once it reaches a boil I turn the heat down to maintain minimal surface rolling but still boiling, simmering one might say. If I start with six gallons of wort I can see where it would take more heat heat energy to keep it simmering than with a lesser amount of wort but it is still going off at a rate of .75 gallons/hour with that level of simmering. If I put half as much, three gallons, of wort in and maintain the same simmer activity admittedly it should take less energy but it is still going of at a rate of .75 gallons/hour. If I lower the energy input enough to end up with only .375 gallons per hour evaporation I don't think it would be boiling at all.

So what is the significance of aiming for a certain percentage of boil off rather than a certain rate of boil activity?

 

[Carolina_Matt]

i can boil 7 gallons with, according to my kill-a-watt meter and fan speed controller, 600-700 watts.....

I brewed a batch today and turned off the 500W element when I reached a boil. So I used 1000W instead of 1500W. My boil-off used to be about 0.8 gallons/hour, but it was only 0.5 gallons today. With 6 gallons pre-boil, that's an 8.33% rate. I'll go with this from now on.

I may be able to get away with just the 500W element if the kettle is partially covered, but I was happy with how things went today. There was a simmer on the surface of the wort, but it wasn't a rolling boil.

 

[bracconiere]

I brewed a batch today and turned off the 500W element when I reached a boil. So I used 1000W instead of 1500W. My boil-off used to be about 0.8 gallons/hour, but it was only 0.5 gallons today. With 6 gallons pre-boil, that's an 8.33% rate. I'll go with this from now on.

I may be able to get away with just the 500W element if the kettle is partially covered, but I was happy with how things went today. There was a simmer on the surface of the wort, but it wasn't a rolling boil.

when i boil at those wattages i mentioned, it is covered

 

[pricelessbrewing]

Not to mention that modern malts, Pils malts included, have negligible SMM in the first place. And apart from Pils malts, it's virtually non-existant. Completely covered boils (apart from a steam stack with condensate drip catch) have been common commercially for some time.

I've heard this repeatedly, and I do believe it's true, but do you have a source for this? I've never seen SMM listed on a maltster spec sheet.

 

[mabrungard]

I've never seen SMM listed on a maltster spec sheet.

Yeah, I don't recall seeing SMM content. But I'm not going so far as saying that Pils malts have less content than before. Maybe maltsters have finally perfected a way to malt and kiln a Pils malt that reduces the SMM content, but there is a lengthy study conducted in the 80s or 90s that documented how it was essentially impossible to end up with a pale enough malt AND low SMM content. They found that just kilning a couple lovibond darker could really make a substantial SMM reduction. So unless you really need a really pale colored beer, using a pale ale malt (say 3L to 5L) can make a notable difference in SMM and DMS compared to using pils malt (1.2L to 2.5L).

Therefore, I'm leery of NOT doing anything to address DMS in beers with high pils content. A period of covered simmering followed by a period of open boiling is still needed based on my research and experience.

 

[pricelessbrewing]

Yeah, I don't recall seeing SMM content. But I'm not going so far as saying that Pils malts have less content than before. Maybe maltsters have finally perfected a way to malt and kiln a Pils malt that reduces the SMM content, but there is a lengthy study conducted in the 80s or 90s that documented how it was essentially impossible to end up with a pale enough malt AND low SMM content. They found that just kilning a couple lovibond darker could really make a substantial SMM reduction. So unless you really need a really pale colored beer, using a pale ale malt (say 3L to 5L) can make a notable difference in SMM and DMS compared to using pils malt (1.2L to 2.5L).

Therefore, I'm leery of NOT doing anything to address DMS in beers with high pils content. A period of covered simmering followed by a period of open boiling is still needed based on my research and experience.

Thanks Martin. So would the same apply to things like "extra pale ale malt" that's sub 3L?

 

[Robert65]

Maybe maltsters have finally perfected a way to malt and kiln a Pils malt that reduces the SMM content, but there is a lengthy study conducted in the 80s or 90s that documented how it was essentially impossible to end up with a pale enough malt AND low SMM content.

Kunze discusses modern malting practices manipulating kilning times and temperatures to achieve color below 4 EBC, SMM not exceeding 4-5 ppm dry basis, and still keeping TBA below 15. He indicates that maltsters are now expected by brewers to deliver this sort of malt, as they demand to be able to achieve acceptable DMS levels with their modern, limited, boiling methods. It seems that the responsibility for control of DMS has been largely shifted from brewer to maltster. In German commercial practice the critical focus in the brewhouse is not boiling, chasing one's tail trying to form and evaporate DMS, but rapid cooling to avoid further thermal splitting of SMM. This is an area homebrewers could benefit from giving more priority. If conducting a whirlpool, it is critical to cool the wort to below 185°F immediately after ceasing boiling and before commencing the whirlpool stand. At this point no more DMS will form, and any free DMS remaining will be scrubbed out in fermentation.

 

[Qhrumphf]

I've heard this repeatedly, and I do believe it's true, but do you have a source for this? I've never seen SMM listed on a maltster spec sheet.

Sitting through enough maltster presentations at conferences. As @Robert65 said, there's an understanding by maltsters that low DMS potential is an expectation of brewers purchasing malt.

And Pils malt certainly does have higher DMS potential than darker base malts, wasn't trying to imply that it didn't. Rather that a 60 min boil with 5% boil off and a means to keep DMS condensate out is plenty. The open roaring volcanic 90 min homebrew boil is patently unnecessary. I don't treat Pils malt wort any differently than I treat any other wort.

 

[mabrungard]

Thanks Martin. So would the same apply to things like "extra pale ale malt" that's sub 3L?

Nomenclature! Malt names have little to do with their color. I’ve tried to categorize malt in respect to it’s practical usage. Pils malt is less kilned than the malts typically used to brew beers that don’t need to very light which I’ve termed Pale malt.

It’s sad that maltsters use confusing and conflicting terms.