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Fermentation issue

cpapkt

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I am reaching out to my fellow homebrewers about an issue I recently have been experiencing with my fermentation.  The issue is my beer basically stops fermenting around 1.020 instead of the normal 1.010.  My equipment and process have not changed.  I test my mash with iodine to verify the conversion is complete and have been dumping my mash water into my mash tun first to eliminate any temperature issues.  I would always be a little low or high when I put the grains in first and then the mash water. 
My typical process is: Pre heat mash tun, heat mash water to temp, dump mash water into mash tun, mix in grains, test for conversion, drain to boil pot (measure SG), rinse grains with heated water, drain to boil pot (measure SG again), boil, cool wort with wort chiller (do a manual whirlpool to try and center any sediment), transfer wort to glass carboy, add yeast and ferment.  I used to always do a secondary but my didn't on my last batch an noticed it didn't really matter. 
My SG is usually within reason (0.02 points of my recipe) of where my expected SG should be so for my finished gravity to be 1.020 instead of 1.010 or 1.015 it seems like my yeast isn't quite fermenting all the sugars.
Any help or suggestion on what is going on would be helpful.
Thanks,

Steve
 
You didn't mention what temp your mashing at. Higher mash temp convert more unfermentable sugars causing the higher FG. Double check your thermometer for accuracy could of changed.
 
cpapkt said:
I test my mash with iodine to verify the conversion is complete and have been dumping my mash water into my mash tun first to eliminate any temperature issues.

As ihikeut pointed out, we're missing the mash target temperature. Plus, we're missing the target OG.

The iodine test is only telling you when the debranching enzymes have completed their work, which is usually 15 to 20 minutes. This creates long chain dextrines, which still need time to further reduce into maltose, glucose and short chain dextrines like maltotriose. Generally a 45 minute rest is the right amount to get the optimal mix of fermentability and body, but you can't go wrong with the 60 minute traditional time.

 
I try to mash in around 153 degrees for 45 minutes.  My measured SG for both batches were 1.055 (target SG of 1.062) and 1.054 (target SG 1.070).  I checked my notes for both batches and saw my mash temp was 158 and 159, respectively.  Seems like that might be my problem to pay attention to. 

Any other tips, suggestions, etc. would be helpful but I will pay much closer attention on my next batch.  I'm planning on making some kind of stout.  Thinking about a traditional stout or an imperial one.
 
personally I'd be a bit more driven to hit your SG targets, which look to be off by quite a bit, than to hit your FG goal.  Are you consistently falling short?  Time to reduce your efficiency?
 
I've only had issues with my last couple batches of beer.  My target gravity is usually pretty good but I would always finish around 1.010 or 1.015.  I'll use these tips and suggestions in my next batch.
 
cpapkt said:
I try to mash in around 153 degrees for 45 minutes. <snip> I checked my notes for both batches and saw my mash temp was 158 and 159, respectively. 

Yes, that'll create a very full bodied beer.

Have you correctly set the mashtun parameters in your equipment profile? By inputting the correct weight and specific heat of your cooler, you'll get a more accurate strike water temperature from BeerSmith. Unless you're preheating the mashtun, click the "Adjust Temp for Equip" box found in the mash window above the temperature steps.

Below the mash temperature steps is a place to input the grain temperature (just put a thermometer in the middle of the grain) and the mashtun temperature (assumed to be the same as the room it's stored in). This will further refine the strike temperature. Then, simply be accurate with the amount of water you're adding. Too little and the mash will be low, too much and it'll be a little warm. Typically the difference is a degree or so, which isn't bad. However, 5 to 6 is problematic.
 
brewfun said:
cpapkt said:
I try to mash in around 153 degrees for 45 minutes. <snip> I checked my notes for both batches and saw my mash temp was 158 and 159, respectively. 

Yes, that'll create a very full bodied beer.

Have you correctly set the mashtun parameters in your equipment profile? By inputting the correct weight and specific heat of your cooler, you'll get a more accurate strike water temperature from BeerSmith. Unless you're preheating the mashtun, click the "Adjust Temp for Equip" box found in the mash window above the temperature steps.

Below the mash temperature steps is a place to input the grain temperature (just put a thermometer in the middle of the grain) and the mashtun temperature (assumed to be the same as the room it's stored in). This will further refine the strike temperature. Then, simply be accurate with the amount of water you're adding. Too little and the mash will be low, too much and it'll be a little warm. Typically the difference is a degree or so, which isn't bad. However, 5 to 6 is problematic.

If you overshoot by 5 or 6 degrees but get the temp down to the goal within a few minutes, is this problematic?
 
jtoots said:
If you overshoot by 5 or 6 degrees but get the temp down to the goal within a few minutes, is this problematic?

Great question.

It takes about 10 minutes for the water to saturate the grain enough that all the enzymes are liberated. So, that's your window of time to correct the temperature. Even then, you still have another 5 minutes before beta amylase activity degrades too far. At that point, it just takes a lot longer to create fermentability.
 
brewfun said:
jtoots said:
If you overshoot by 5 or 6 degrees but get the temp down to the goal within a few minutes, is this problematic?

Great question.

It takes about 10 minutes for the water to saturate the grain enough that all the enzymes are liberated. So, that's your window of time to correct the temperature. Even then, you still have another 5 minutes before beta amylase activity degrades too far. At that point, it just takes a lot longer to create fermentability.

good to hear, thank you! 
 
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