Inconsistent fermentation in similar temperature conditions

[rjenman]

Hi

I have made a pretty good brew that consistently starts at about 1.032 SG and usually ends at 1.010 , however twice now it's ended at 1.020

(I'm brewing an ale, leaving it in a fermenter for 7 to 10 days , taking the "end" SG reading and then bottling it up.)

I'm trying to figure out what's going wrong with the batches that end at 1.020 ... the first was in a cold spell in Brisbane, with temps likely several degrees below 12C and adding more Yeast and leaving it for another week did nothing (assuming it died).

Surprisingly, despite the SG remaining at 1.020, bottling the beer resulted in beer with full strength alcohol content. As i assumed the SG would reflect alcohol content. However it has a very thick and unrefined, comparatively dirty sort of consistency and is "drinkable" rather than "good"

I assumed it was temperature, but now I've just done a batch in perfect weather (15C to 22C all day every day) and it's happened again. Does anyone have any idea as to the factors causing this? My only guess is that brewing without temperature control is inconsistent in results and maybe I should double the yeast I put in to make it work, but I'm very thrown off by the fact it still seems to have full alcohol content.

I guess it could be the temperature that I Mash, but I'm skeptical that it makes that much difference. I may try really carefully to recreate the temperature conditions recorded on my successful batches to make the wort identical. But I find it hard to believe that 10 degrees celcius mashing malt makes such an extreme difference in the quality of the beer.

Have a good one and don't drink too much

 

[Hoochin'Fool]

Any advice beyond "you're bottling WAY too soon", would require knowing:

• The grain bill
• The yeast
• The mash temperature and duration (it can make a pretty big difference)

update:
Just saw your introductory post, where you mention "I make my own malt and brew it into an ale".
So how consistent is your malting process?

 

[rjenman]

Thanks for your reply. As I said I attempted to leave the first out out for another week with more yeast and nothing happened. I've currently got the second bad batch in the fermenter I might leave that out for a month just to experiment with it and see what happens to the SG.



I've decided pretty soon after I posted that it's probably the mashing process. The batches I made that turned out really good did have some periods of extremely high temperature. I'll have to simultaneously check HOW LONG exactly that was compared to the temperature spikes in the bad batches. But simultaneously I think I'll attempt a batch with strictly low temperature (attempting to minimize unfermentable sugars) (Since when it mashed up to below 1.030 I would get a little aggressive with raising the temperature to get the SG up there). But as I said I've recorded the temps in the successful brews so I'll hopefully get a consistent brew that tastes as good as the successful batches without just eliminating ALL the unfermentable that got in there and made it taste so good.



Making the malt was relatively consistent. The amount the barley sprouted was relatively consistent with no major differences, although I'm open to that being an issue. The drying back was more aggressive in some batches of malt as when I malted them all I dried them all back at exactly the same temperature (in most cases) but left it in the dehydrator for a substantially long time in some situations when id found it to be too wet to reliably mill.

I'll focus on the mashing process and I'd like to make this efficient without becoming a Nazi about the malting process (i.e. getting really strict with malting parameters when it turns out that it was a waste of time to be so strict with things that didn't change the successful beer)

I'll reply to this post when I figure out a very consistent answer to the question although obviously that might take a while

Thanks again for reply

 

[Hoochin'Fool]

Definitely take care on your mash temperatures! I use software (Brewer's Friend) that tells me what temp to heat my water to, so that when I add my grain it will cool down to my desired mash temp (usually 151 F, or about 66 C). Then I remove from heat, cover with a lid, and my reflectix insulation wrapped kettle only loses a degree or two over the next 60 minute mash.

 

[Hoochin'Fool]

Have you ever considered skipping the malting process, and using amylase enzyme to convert your (raw) barley at mash temp? That's gotta be cheaper faster (and less energy intensive) than sprouting your grain and then drying it back out. (disclaimer: I know nothing about malting grains)

 

[rjenman]

Interesting thing to say, as I found that my hot water straight out of the tap is within the parameters for mashing. I found in theory I could simply turn the tap on and fill up the mashing pot with the malt in there. But I found I had to raise the temp a bit to get the SG up. And the levels I've raised the temp exactly have been slightly erratic (although recorded). But I've definitely made a really good beer more than once so I'll have to really objectively figure out what I did right with those temperatures because every time, the mash went way way way over temperature for a medium to short period of time which obviously contributed to an overall good flavor

 

[rjenman]

Have you ever considered skipping the malting process, and using amylase enzyme to convert your (raw) barley at mash temp? That's gotta be cheaper (and less energy intensive) than sprouting your grain and then drying it back out. (disclaimer: I know nothing about malting grains)

Is that a standard thing that's been done with beer? Is it done with some other spirits or something? I've never heard of it. I find it hard to believe this possible as malting the grain involves the grain becoming mushy and chemically changing with the sprouts, and then when you dry it back it becomes basically a powdery sugary substance, I find it hard to believe you can get that without malting it

 

[day_trippr]

Definitely not a "standard" practice, but an interesting one...

https://www.forbes.com/sites/dontse...-hopes-to-revolutionize-the-way-beer-is-made/

 

[Hoochin'Fool]

Definitely NOT standard, LOL! But it seems like it should work -- the whole point of malting is to unlock the amylase enzymes in the grain.

 

[DBerg]

Rjenman, have you calibrated your hydrometer? I just bought a new one because the scale in my old one was moving, I had to calibrate before every measurement and it changed a lot!

 

[rjenman]

Definitely not a "standard" practice, but an interesting one...

https://www.forbes.com/sites/dontse...-hopes-to-revolutionize-the-way-beer-is-made/

Interesting chat indeed. I might look into that but the traditional malt making process is easy but labour intensive. I'll confirm that I can actually do it properly in a few months but the entire thing is quite rustic and charming. It's just labor intensive and you go through a bit of water, not that much really, maybe 20L of water to make 10kg of malt. Apart from that it's just electricity in drying it back and possibly consistency issues that I'm addressing.

 

[Bobby_M]

Less than 1% of brewers are malting their own so getting specific advice about that is going to be tough. The odds of malting on a precision level as the maltsters do is unlikely. I would recommend running the mash through a 20 minute protein rest and slowly ramping into the sacharification zone. Are you measuring gravity with refractometer?

 

[doug293cz]

I guess it could be the temperature that I Mash, but I'm skeptical that it makes that much difference. I may try really carefully to recreate the temperature conditions recorded on my successful batches to make the wort identical. But I find it hard to believe that 10 degrees celcius mashing malt makes such an extreme difference in the quality of the beer.

The usable mash temperature range is about 63°C (145°F) to 71°C (160°F), which is a range of only 8°C. So, 10°C variation in mash temps is too much. At the high end of the temperature range the alpha amylase enzyme starts to denature rapidly, and may get completely denatured before starch gelatinization and hydrolysis are complete, thus reducing wort fermentability (incomplete hydrolysis leaves more unfermentable dextrins in the wort, and maybe even some soluble starch.) At the low end of the temp range, gelatinization proceeds slowly, so you need more time to complete gelatinization, which must happen before you can complete hydrolysis. Also, at lower temps the limit dextrinase (the enzyme in malt that hydrolyses the branching bonds in starch) denatures more slowly, allowing more of the branched dextrins to be converted to fermentable sugar. This is why low temp mashes generally result in higher fermentability wort than higher temperature mashes. The commonly used range for mashing is about 64°C (147°F) to 69°C (156°F.)

As I said I attempted to leave the first out out for another week with more yeast and nothing happened. I've currently got the second bad batch in the fermenter I might leave that out for a month just to experiment with it and see what happens to the SG.

Your high FGs may be the result of low fermentability wort (due to inadequate mash conditions), and have nothing to do with fermentation conditions or yeast health. A way to test this is to add alpha amylase enzyme (readily available at brew supply stores) to the fermenter. In many cases this will allow the non-limit dextrins to be hydrolyzed to fermentable sugar, and allow fermentation to continue. If alpha amylase in the fermenter fixes your high FG issues, then you know the root cause was the mash conditions.

Here's a recent success story about using alpha amylase in the fermenter to reduce high FG which was due to low wort fermentability. Report of success starts around post #50.

I've decided pretty soon after I posted that it's probably the mashing process. The batches I made that turned out really good did have some periods of extremely high temperature. I'll have to simultaneously check HOW LONG exactly that was compared to the temperature spikes in the bad batches. But simultaneously I think I'll attempt a batch with strictly low temperature (attempting to minimize unfermentable sugars) (Since when it mashed up to below 1.030 I would get a little aggressive with raising the temperature to get the SG up there).

I found I had to raise the temp a bit to get the SG up.

Higher mash temps allow gelatinization to proceed much more rapidly, making more starch available for hydrolysis sooner in the mash. This can allow more complete hydrolysis during the allotted mash time, resulting in more fermentable wort. But, if the higher temps are not well controlled, you can denature the alpha amylase before gelatinization and hydrolysis are complete, in which case you will end up with lower fermentability wort. So, this higher temp mashing must be carefully controlled. Accurate temp measurement and control are critical.

A simpler way to make sure you get good fermentability,and maximum conversion efficiency, is to limit the max mash temp to something under 69°C, and extend the mash time until the SG stops increasing. This is pretty easy to do if you have a refractometer, so you can easily sample the SG of the wort during the mash. A usable protocol is to mash for 60 minutes (or whatever your standard time is), stir the mash aggressively to homogenize the wort (to avoid the effects of wort stratification), and then measure the SG. Let the mash go another 10 - 15 minutes, and repeat the SG sampling and measurement. Continue this until the SG stops increasing between successive samples.

If you want to maximize wort fermentability, then doing a step mash with an initial saccharification rest between 64°C and 65.5°C for 30 - 45 minutes, followed by a rest at 68°C to 69°C until SG stops increasing is a good way to go. @Bobby_M 's suggestion is also a excellent approach. A ramp rate that takes ~60 minutes to go from 64°C to 70°C, and then hold at 70°C until SG maxes out is a good place to start.

Brew on