Mash temperature vs ABV

[TomVA]

I brewed two 3.5 gal BIAB batches of stout with the same grain bill, hops bill, and yeast (11.5 gr of rehydrated S-04). The only significant differences were that batch #1 was mashed at 160°F (OG = 1.050) and was fermented at 63°F, while batch #2 was mashed at 156°F (OG = 1.055) and fermented at 66°F. Both beers tasted great, but batch #2 had 30% more alcohol than batch #1 (4.6% vs 3.5%).

Both fermentations were for four weeks and both were roused and finished at about 70°F, so I would think the fermentations were complete. And all gravities were meticulously measured with a calibrated hydrometer. Given that the post-mash gravity and the OG of batch #2 were significantly higher than batch #1, that leaves the mash temperature as the main culprit in explaining the difference in ABV.

I expected that mashing at a higher temperature would produce more unfermentable sugars, but did not expect that only 4°F would make that big of a difference in ABV. Is the ABV that sensitive to mashing temperature?

TomVA

 

[Oginme]

You don't give us the final gravity readings, but based upon your OG of 1.050 vs 1.055, you have a different mash efficiency for each batch. If they finished at the same final gravity, then that additional .005 in the gravity readings would account for 0.5% difference in ABV just by itself. A difference in finishing gravity could easily account for the rest, which would be driven by the mash temperature.

For my system and my thermometer, a 160F mash temperature would lead to much less fermentability in wort than a batch mashed at 156F, but I am not sure it would account for a difference in finishing gravity of 1.016 (for the 1.050 wort) and 1.011 (for the 1.055 wort) that would give you the difference in ABV from 4.6% (for the 1.055 wort) to 3.5% (for the 1.050 wort) even if they were fermented at the same temperatures.

Between the difference in mash efficiency and gravity achieved between the two batches suggests that they are not the same wort going into the fermenter. The difference in fermentation temperature further would give them a differentiation which can account for some of the difference as well.

With these changes, it is really hard to make a direct comparison and draw any firm conclusion on the effect of mash temperature in your process.

 

[hvjackson]

I expected that mashing at a higher temperature would produce more unfermentable sugars, but did not expect that only 4°F would make that big of a difference in ABV. Is the ABV that sensitive to mashing temperature?

If you had mashed at 150 ºF and 154 ºF I would expect them to be closer, but at 160 ºF you are right at the upper range of reasonable mash temps, so my guess is that is why that batch had much lower fermentable content.

 

[mabrungard]

Certainly! Attenuation is highly correlated with mashing temperature, but another factor is the duration of mashing since it takes time for the enzymes to convert less digestible sugars and dextrins into highly fermentable sugars. While there is plenty of evidence from brewers and journals that show that a mash can generally convert all starches in the mash to sugars, it still takes more time to cut those poly-saccharides into fermentable sugars. So, you haven't presented all of your mashing information needed to assess the differences.

I do like to employ an approach to fermentability that varies with respect to the wort's original gravity. In general, low gravity beers are mashed at higher temps (nearing 160F) for shorter time, while high gravity beers are mashed at lower temps (say mid 140's F) for longer periods. Of course, this approach should be applied on a somewhat linear scale for beers of middling gravities.

 

[Denny]

I have found that most malts, especially domestic malts, have so much diastatic power that mash temp doesn't make a lot of difference unless you vary it greatly. 4F will make no detectable difference so something else must have happened.

 

[Lefou]

I ALWAYS assume the higher gravity beer will produce a higher potential ABV if your diastatic conversion rate is constant. A lower mash temp favors a better conversion to sugars your yeast can consume.
Looking at the math, S-04 attenuation is 75%. The higher gravity beer will always yield a higher ABV if everything else is constant.

 

[TomVA]

Here is some more data on the two batches:

.........................................Batch#1.............................Batch#2

Mash Temperature.................160....................................156
Post Mash Gravity.................1.042.................................1.045
Original Gravity....................1.050.................................1.055
Final Gravity........................1.023.................................1.020
ABV %..................................3.5.....................................4.6

TomVA

 

[ircbrewing]

This totally makes sense. At mash temperatures of 148-151 you get more alpha amylase and 153 -157 you get more beta amylase from your grains. 152 is typically viewed as the mash temp where you get approximately equal amounts of alpha and beta amylase.

Alpha amylase is an enzyme from the grains that produces more fermentable sugars which will increase attenuation and thus your ABV. It will also produce a drier beer as the yeast can process further down the sugar chains.

Beta amylase is an enzyme that produces fermentable sugars but they are more difficult for yeast to process, thus mashing in a beta range will produce a sweeter beer with lower attenuation and alcohol as the yeast aren't able to process down the sugar chain.

Your results above back this up, though I would never suggest mashing a temp higher than 157 on the top end or mashing lower than 147 on the low end.

Your beer mashed at 160 gave you a lot of beta amylase in your wort, which are less fermentable, which is why that beer finished at a sweeter FG of 1.023.

At 156, you are mashing at beta acceptable temperature which have you more fermentable sugar, which is why the yeast attenuated better and you ended up with a lower FG even though this beer started .005 higher in OG than the other beer.

Mash temperature is so important in the final product. Are you looking for something drier? Then Mash at 147-150. Something with more body and a sweeter touch? Mash at 153-157.

 

[JONNYROTTEN]

I have found that most malts, especially domestic malts, have so much diastatic power that mash temp doesn't make a lot of difference unless you vary it greatly. 4F will make no detectable difference so something else must have happened.

This is what I found also. I always hit my numbers brewing the same beer whether I mash at 150 or 158. The mouthfeel is the same also. I know I'm "Supposed" get a drier beer low and sweeter beer high mash. Maybe its my palate but the grain bill is the only thing that makes a difference.

 

[eric19312]

Here is some more data on the two batches:

.........................................Batch#1.............................Batch#2

Mash Temperature.................160....................................156
Post Mash Gravity.................1.042.................................1.045
Original Gravity....................1.050.................................1.055
Final Gravity........................1.023.................................1.020
ABV %..................................3.5.....................................4.6

TomVA

Hi Tom
How did you measure final gravity? Is this hydrometer or refreactometer? Seems like extreme low attenuation otherwise...

 

[TomVA]

Hi Tom
How did you measure final gravity? Is this hydrometer or refreactometer? Seems like extreme low attenuation otherwise...

I measured all gravities with a hydrometer I calibrated with water @ 60°F and corrected all readings to 60°F.

In both batches I designed the grain bill to aim at about 5.0% ABV using Brewer's Friend and pretty much hit the predicted OG of 1.053, but the attenuation was not as expected. Four weeks in primary with S-04 and temperatures in the low-mid 60s certainly should have done the job on fermentables. It's the low ABV of the first batch that surprised me and led me to think that the very high mash temperature may have left more unfermentables behind.

In looking back at some of my brown ales, three batches mashed at 160°F came in with ABVs well below expected, and two mashed at 156-158°F came in closer, so there seems to be a correlation (as expected), but more sensitive than I expected.

TomVA

 

[Denny]

This is what I found also. I always hit my numbers brewing the same beer whether I mash at 150 or 158. The mouthfeel is the same also. I know I'm "Supposed" get a drier beer low and sweeter beer high mash. Maybe its my palate but the grain bill is the only thing that makes a difference.

I mashed the same recipe at 153 and 165. Identical results.

 

[eric19312]

I measured all gravities with a hydrometer I calibrated with water @ 60°F and corrected all readings to 60°F.

In both batches I designed the grain bill to aim at about 5.0% ABV using Brewer's Friend and pretty much hit the predicted OG of 1.053, but the attenuation was not as expected. Four weeks in primary with S-04 and temperatures in the low-mid 60s certainly should have done the job on fermentables. It's the low ABV of the first batch that surprised me and led me to think that the very high mash temperature may have left more unfermentables behind.

In looking back at some of my brown ales, three batches mashed at 160°F came in with ABVs well below expected, and two mashed at 156-158°F came in closer, so there seems to be a correlation (as expected), but more sensitive than I expected.

TomVA

OK...
1.050 -> 1.023 = 52.8% apparent attenuation
1.052 -> 1.020 = 62.4% apparent attenuation

you may have demonstrated a big increase in fermentability going from 160 to 156

But...
You are so far from expected 75% apparent attenuation for this yeast that you have to consider something else could be going on. Maybe your mash temperature thermometer is not calibrated. Maybe your refractometer has a hairline crack in it. Maybe the beer in FG hydrometer sample was a little carbonated. 52% attenuation is not at all likely with this yeast with a normal strength grain bill. Something more than mash temperature issue is going on here.

 

[TomVA]

OK...
1.050 -> 1.023 = 52.8% apparent attenuation
1.052 -> 1.020 = 62.4% apparent attenuation

you may have demonstrated a big increase in fermentability going from 160 to 156

But...
You are so far from expected 75% apparent attenuation for this yeast that you have to consider something else could be going on. Maybe your mash temperature thermometer is not calibrated. Maybe your refractometer has a hairline crack in it. Maybe the beer in FG hydrometer sample was a little carbonated. 52% attenuation is not at all likely with this yeast with a normal strength grain bill. Something more than mash temperature issue is going on here.

Yes, that's what I am trying to figure out, i.e. just how sensitive is mashing temperature. It does indeed sound like something else is going on, but my last two Best Bitter batches fermented for half the time with the same yeast at the same temperature, but mashed at 154°F, hit their numbers, giving 72% and 77% attenuation.

Per instructions I hydrate the S-04 at 80°F and it cools to about 78°F in 30 minutes, when I pitch it into 70°F wort. I slightly over pitched the yeast in these two stout batches, adding a full packet (11.5 g) to a 3.5 gallon batch.

My digital thermometers were checked in ice water and boiling water and were spot on, and my hydrometer is calibrated in water (as a retired chemist/lubricant formulator and frequent vegetable canner I tend to be anal about these things. I even keep a detailed spreadsheet on every batch.)

I appreciate everyone's comments!!

TomVA

 

[ncbrewer]

I was having consistent high FG for a while. These are the things I tried:
Maintain constant temperature while hydrating (without stirring) [This didn't help]
Minimize time between starting rehydration and pitching (less than 30 minutes)
Added ~3/4 oz wort after attemperation if waiting too long to pitch.
Keep max of 18 deg temp drop per cool-down step during attemperation
Reduced rehydration water from 8 oz to 6 oz before boiling [This didn't help]
Pitch dry [This didn't help]
Varied pitching temperature
Yeast hydration temperatures (may be strain dependent)
Yeast nutrients
Yeast hydration - water problems (tried using spring water w/o chlorine)

I greatly improved the attenuation using a combination of several of these, but I never backed off of some to determine which specific procedures were responsible for the improvement. Maybe some of these things will help with your problem.

 

[TomVA]

I was having consistent high FG for a while. These are the things I tried:
Maintain constant temperature while hydrating (without stirring) [This didn't help]
Minimize time between starting rehydration and pitching (less than 30 minutes)
Added ~3/4 oz wort after attemperation if waiting too long to pitch.
Keep max of 18 deg temp drop per cool-down step during attemperation
Reduced rehydration water from 8 oz to 6 oz before boiling [This didn't help]
Pitch dry [This didn't help]
Varied pitching temperature
Yeast hydration temperatures (may be strain dependent)
Yeast nutrients
Yeast hydration - water problems (tried using spring water w/o chlorine)

I greatly improved the attenuation using a combination of several of these, but I never backed off of some to determine which specific procedures were responsible for the improvement. Maybe some of these things will help with your problem.

Thank you for these suggestions. I actually do most of them, except I do stir the yeast after 15 minutes of rehydration, I always pitch at room temperature (70°F), and I have no chlorine in my well water. My issues seem to be with dark ales mashed hot, as my bitters attenuate quite well.

Speaking of which, I just had a glass of my Best Bitter and WOW, best beer I have made so far. Felt like I was sitting in a pub in England. Going to brew more of that recipe next, and soon!

TomVA

 

[eric19312]

Yes, that's what I am trying to figure out, i.e. just how sensitive is mashing temperature. It does indeed sound like something else is going on, but my last two Best Bitter batches fermented for half the time with the same yeast at the same temperature, but mashed at 154°F, hit their numbers, giving 72% and 77% attenuation.

Per instructions I hydrate the S-04 at 80°F and it cools to about 78°F in 30 minutes, when I pitch it into 70°F wort. I slightly over pitched the yeast in these two stout batches, adding a full packet (11.5 g) to a 3.5 gallon batch.

My digital thermometers were checked in ice water and boiling water and were spot on, and my hydrometer is calibrated in water (as a retired chemist/lubricant formulator and frequent vegetable canner I tend to be anal about these things. I even keep a detailed spreadsheet on every batch.)

I appreciate everyone's comments!!

TomVA

Helps to understand you are scientist. Possibly consider higher resolution hydrometer? I got one (well and a second one) of this high resolution bottling hydrometers and really like it for final gravity. Fragile as hell but I am no confident in calling FG a 1.010 vs a 1.009 even in a slightly cloudy sample.

 

[VladOfTrub]

One batch had more CO2 or gunk in the test samples. Temperature's 156 and 160F are in the Alpha II and Alpha I range. Find out what Alpha does and the picture will get clearer.
This is what I think happened. Primary fermentation occurs due to glucose. The 156F batch had a higher percentage of glucose due to enzymatic action of Alpha. The temperature was very close to optimum for Alpha during the rest. During the rest Alpha released a better balance of sweet tasting, non-fermenting sugar and glucose and yeast went to work on the glucose. In the higher temp mash Alpha released more non-fermenting sugar and less glucose. It is difficult to measure efficiency, ABV and attenuation accurately without using the device that does it. There are a lot of variables. A hydrometer measures pressure and that's about it. The device is quite expensive. Something else to consider, the black malt reduced the mash pH and assuming everything was the same in both batches, brewing water and everything except for temperature, mash pH may have been more optimum in a batch due to the rest temperature being optimum for the enzyme. What I mean is that since there is an optimum temperature for an enzyme the pH must be optimum as well. If they are not in sync enzymatic action changes.
A note about efficiency. When malt is soaked in hot water for an hour or so a certain type of complex starch called amylo-pectin is floating around in the mash. The thing about the starch is that it is heat resistant and it doesn't rupture and begin to enter into solution until mash temperature reaches 169F. During single infusion mashing at no time are temperatures high enough to rupture the starch and if the high temperature were used enzymes would denature. The starch goes with the spent mash to the compost heap, it's the small white pieces. The starch is amylo-pectin and it is responsible for the body in beer. Alpha releases limit dextrin as it liquefies the starch chain. The types of sugar are called A and B limit dextrin. The sugar is tasteless and non-fermenting. So, when considering efficiency, consider that you are throwing money on the compost heap. Also, consider the beer that you are producing, it is missing the starch that beer kind of needs to be beer. There's little more to focus on than efficiency.
Mash is boiled in the decoction method without denaturing enzymes.

Quote...."This totally makes sense. At mash temperatures of 148-151 you get more alpha amylase and 153 -157 you get more beta amylase from your grains. 152 is typically viewed as the mash temp where you get approximately equal amounts of alpha and beta amylase.
Alpha amylase is an enzyme from the grains that produces more fermentable sugars which will increase attenuation and thus your ABV. It will also produce a drier beer as the yeast can process further down the sugar chains."

If what you wrote came from a book on making beer throw the book away and if it came from the internet, the person that put it there knows nothing about enzymes or you are pretty much confused, which does happen and that's OK because you are probably just beginning. I'll help you out.

You might not realize this but, Alpha works very well at 98.6F, saliva is loaded with it. Chew up a big chunk of bread for about 10 minutes and it begins to taste sweet.
Alpha amylase is the most prolific and strongest enzyme in the kernel of grain. It activates at temperatures from cool, earth temperature in the spring up to 168F where it denatures. The enzyme releases two types of sugar from simple starch called amylose. When Alpha liquefies the starch chain it does it at a place called a 1-4 link. When that happens two chains are created. Alpha continues to work on the chain called the reducing end because there are more 1-4 links in the chain. When there are no longer any 1-4 links for Alpha to liquefy, sweet tasting, non-fermenting sugar is left. The other chain is the fuel for yeast, people and the plant from where the kernel came from, it is a simple sugar called glucose. Alpha converts starch into nothing, it liquefies/softens starch. The correct term is mash conversion.
We'll get into conversion next.

Beta is a low temperature activated enzyme. Activation range is around 130ish and optimum temperature range is 140 to 145F. Beta is a weak enzyme and temperature above 145F denatures the enzyme quickly. Beta is the enzyme responsible for first conversion. Beta converts the glucose that Alpha releases from amylose into complex types of sugar called maltose and malto-triose, di and tri-saccharides. Conversion occurs when Beta converts simple sugar into complex sugar and it occurs during the maltose rest.
Yeast cannot use complex sugar for fuel, only simple sugar and due to that a type of second conversion occurs during the second fermentation cycle. During second fermentation yeast absorbs maltose and enzymes within yeast converts the maltose back into glucose. The glucose is expelled through the cell walls and it becomes fuel. Gravity reduces. During the aging phase yeast does the same thing with malto-triose and natural carbonation occurs.
The malt that works with single infusion and which most home brewers purchase is high modified malt. The enzyme richness isn't the best in high modified malt and because of it the low temperature enzymes are pretty much non-existent or they are very weak and will not do anything. There are no reasons to use any temperature except for the optimum temperature for Alpha. It would be a waste of time. Vis versa, purchasing a more expensive, higher grade malt and soaking it in hot water at one temperature for an hour would be a waste of money.