Fly Sparge and Mash-out high FG problems

[TucsonBrew]

I am trying to dial in my brewing process to hit a specific brewing profile. For awhile when I was first getting into brewing I would not do a mash-out and regardless of what temp I mashed at my FG was always 1.010. I understand why this is the case with flysparging in particular due to the enzymes remaining active during the long sparge process.

So about a year ago I began doing a mash-out using direct heat, a false bottom in my mash tun, and a pump to recirculate as I heated. Usually taking 15-20 minutes to heat to 168. Since then I now usually have a FG of around 1.020 regardless of recipe variations and different mash temps(although about 10% of the time I will hit my intended FG and I can not identify any difference in my process on those brews that would explain this). I thought that by recirculating I would not be likely to be scorching the wort during my direct heat process or doing anything that would negatively impact the sugar profile I was trying to achieve. So naturally I started trouble shooting other factors that can lead to lead to high FG results. I had come to the conclusion that it must be an oxygen issue since I usually do higher gravity beers. So I was about to invest in a oxygen tank setup. Before I did that I decided to re-brew a batch I did recently that had finished high and this time not mash-out but keep the rest of my process the same. My FG on this batch was 1.010.

So now I think I must be damaging the wort in some way during my direct heat process but I am at a loss where my problem is. Has anyone else run into this problem? I really just want to be able to consistently hit the FG that I am designing my recipe for and I know I can't do that without mashing out in some fashion.

I should mention that I have checked the accuracy of my hydrometer and thermometers so I do not think these are the cause of the problem.

Sorry to create a new thread, just having a hard time finding an answer to this problem.

Thanks for the help.

 

[VladOfTrub]

What may be happening; when you are beginning to ramp up the mash temp from final conversion temp to 168F, the mash may stay long enough in the alpha 1 temp range of 158 to 162F to produce more non ferms. Also, starch begins to burst around 168F. Maybe excess starch carry over? I'm not sure if starch offsets an hydrometer reading.

 

[TucsonBrew]

Thanks for the reply.

I always do an iodine test at the end of the mash. If that test indicates that starch conversion is complete can there still be any significant starch left in the mash to burst as you describe, or continue converting? Also, I thought that once a mash at a lower temperature (on most of my recipes I mash at 150 to 154 degrees) has been completed the starches will have been converted to short chain sugars which are fairly easily fermentable. Even if different enzymes are active while I am raising from conversion temp to mashout I did not think those enzymes could do anything to make the existing short chain sugars more complex or non-fermentable at that point? That is why I was thinking maybe I am somehow caramelizing the sugars or something during my reheat process.

 

[jCOSbrew]

Mash temp is one factor. The other major factors are years and O2. All 3 will effect your FG.

Try yeast starters, pure 02, and ramping temp at the end of fermentation for a lower FG.

 

[TucsonBrew]

I typically use a 1.5 liter starter. I use Beersmith to calculate the cells I need and use a stirplate. I have tried ramping up the temp to as much as 76F once primary fermentation seems to have halted. I have also tried gently agitating the fermenter to rouse the yeast and have tried adding a few ounces of priming sugar to try to encourage yeast activity (I saw this recommended in an article on this site). None of the above has been helpful. I have not yet tried direct O2. But when I just brewed a recipe that had stalled at 1.020 on a previous batch and this time it finished at 1.010 (the only change in procedures being no mashout) that seemed to indicate that it was not an oxygen problem. I realize this is not a scientific conclusion, but I would have thought that if it was a problem of insufficient aeration the latest batch would still have stalled somewhat high despite the more fermentable wort, although maybe in the mid teens instead of 1.020. That is why I thought it might be a problem caused by my direct heating of the mashtun for mashout.

 

[BuzzKillington]

I am having the same issues as the OP. I just made a simple IPA with an OG of 1.069 and now after a week its down to around a 1.019. For this batch I did a mash out from 149* to 168* over a 15 minute time frame, my total mash time was 90 minutes. The yeast I am using is WLP 090. I oxygenated this batch for 90 seconds with a pure oxygen setup.
I normally don't do a mash out so I was thinking that may be the issue. Even though it's only been a week in the carboy, I think my FG is not going much lower.

 

[TucsonBrew]

Seems like 90 seconds of direct O2 should be enough aeration for that size beer. Out of curiosity, how stiff did you mash on that batch? I was just reading some passages in John Palmer's book and he mentions briefly that a stiffer mash might inhibit enzyme activity and result in a less fermentable wort even if conversion is complete. I frequently mash as stiff as 1.25 quarts per pound. For some reason I was thinking that it would not cause problems until you get as stiff as 1/1. The few batches that I have brewed this past year that finished at a reasonable FG my mash was more like 1.4 to 1.6 to 1. Maybe that is a factor.

 

[BuzzKillington]

Seems like 90 seconds of direct O2 should be enough aeration for that size beer. Out of curiosity, how stiff did you mash on that batch? I was just reading some passages in John Palmer's book and he mentions briefly that a stiffer mash might inhibit enzyme activity and result in a less fermentable wort even if conversion is complete. I frequently mash as stiff as 1.25 quarts per pound. For some reason I was thinking that it would not cause problems until you get as stiff as 1/1. The few batches that I have brewed this past year that finished at a reasonable FG my mash was more like 1.4 to 1.6 to 1. Maybe that is a factor.

I had a ratio of 1.5 to 1, seems to be a happy medium.