1st BIAB issues/questions

[BumpyAZ]

Been brewing for about a year and decided it was time to make the jump to all grain. So, after a lot of reading and prep, I recently brewed my first two batches using BIAB. Everything went well and I pretty much hit all of my numbers spot on. However, I had a little issue with the mash temps but I'm not sure if I'm being to anal and over analyzing things. I planned to mash at 150. I used two thermometers to check the temp throughout the mash, a lab thermometer measuring temp in the bottom of the kettle and a digital probe (which I previously tested to read within 1 degree of the lab thermometer) near the surface of the mash. The kettle was kept in the oven on low to maintain consistent temps which was very effective. For the first batch, I stirred once half way through and during most of the mash the temp at the bottom was 152 but 147 at the top. The second batch I stirred three times during the mash. The temps were more consistent throughout the mash, typically 150 at the bottom and 147 at the top. Is this type of variation typical for the average mash? Or should I be looking for a more consistent temp no matter what depth of the mash I'm measuring at?

I also did a mashout on both batches heating the kettle to 170 on the stove after the mash period was done. For the first batch, I put the lid on the pot to start the mash out but forgot to turn off the burner. 5 minutes in, I realized the burner was still on and checked the temp which was 180. I turned off the burner and stirred well until the temp dropped to 170 and I covered it back up until the mash out was over. Do I need to be worried about tannis or anything else since the grain was exposed to higher temps for a few minutes?

Finally, I mis-measured my preboil volume one the second batch. I had to top off slightly by sparging to get to the proper height as measured with a stainless steel ruler. But after doing so, I realized I had left the cooling rack I used to keep the bag off the bottom of the pot in while I made my measurement so I ended up with about a half gallon more volume than I thought I had. I decided to just proceed instead of trying to boil it off. So, my pre-boil gravity was a bit lower than expected. Is there a way to calculate what it would have been if I had the correct volume in the kettle? Thought I had seen a calculator to do this but can't find the site now. Thanks!

 

[doug293cz]

Been brewing for about a year and decided it was time to make the jump to all grain. So, after a lot of reading and prep, I recently brewed my first two batches using BIAB. Everything went well and I pretty much hit all of my numbers spot on. However, I had a little issue with the mash temps but I'm not sure if I'm being to anal and over analyzing things. I planned to mash at 150. I used two thermometers to check the temp throughout the mash, a lab thermometer measuring temp in the bottom of the kettle and a digital probe (which I previously tested to read within 1 degree of the lab thermometer) near the surface of the mash. The kettle was kept in the oven on low to maintain consistent temps which was very effective. For the first batch, I stirred once half way through and during most of the mash the temp at the bottom was 152 but 147 at the top. The second batch I stirred three times during the mash. The temps were more consistent throughout the mash, typically 150 at the bottom and 147 at the top. Is this type of variation typical for the average mash? Or should I be looking for a more consistent temp no matter what depth of the mash I'm measuring at?

Temperature stratification is a known issue with mashing. The best way to minimize it is to stir the mash well at mash in to get uniform temps, then insulate equally around all of the mash vessel so that no part of it transmits more heat to the environment than any other part, and then stirring periodically to rehomogenize the temps. Keeping a kettle in an oven at the mash temp should minimize temp stratification. Not sure why it didn't keep your temps more uniform. Could be your oven has a very non-uniform temp top to bottom, or your thermometers could be reading differently.

I also did a mashout on both batches heating the kettle to 170 on the stove after the mash period was done. For the first batch, I put the lid on the pot to start the mash out but forgot to turn off the burner. 5 minutes in, I realized the burner was still on and checked the temp which was 180. I turned off the burner and stirred well until the temp dropped to 170 and I covered it back up until the mash out was over. Do I need to be worried about tannis or anything else since the grain was exposed to higher temps for a few minutes?

Overheating on mashout will only cause tannin extraction if your mash pH is too high (> 5.8-6). Extracting tannins requires both temps > 170°F and high pH. But then, you don't even need to do a mashout for BIAB (or 3 vessel batch sparging), as long as you get essentially full starch to sugar conversion in the mash. Mashout is primarily to denature the amylase enzymes before fly sparging so that the sugar profile doesn't continue to shift towards higher fermentability during the long sparge time.

Finally, I mis-measured my preboil volume one the second batch. I had to top off slightly by sparging to get to the proper height as measured with a stainless steel ruler. But after doing so, I realized I had left the cooling rack I used to keep the bag off the bottom of the pot in while I made my measurement so I ended up with about a half gallon more volume than I thought I had. I decided to just proceed instead of trying to boil it off. So, my pre-boil gravity was a bit lower than expected. Is there a way to calculate what it would have been if I had the correct volume in the kettle? Thought I had seen a calculator to do this but can't find the site now. Thanks!

(SG@volume2 - 1) = (SG@volume1 - 1) * volume1 / volume2

or
​

SG@volume2 = 1 + (SG@volume1 - 1) * volume1 / volume2

Brew on

 

[wilserbrewer]

I'm not sure if I'm being to anal and over analyzing things.

Yep, maybe a bit IMO , but that's Ok, that's what were here for, feedback. I brew pretty fast and loose...been doing it a while, familiarity builds complacency I guess.

Sounds like your doin fine, except for the little silly mistakes which I'm sure you'll hone out. FWIW I usually stir and then check temp.

Your temp variation could be not enough mixing at dough in...I am always surprised how much mixing it takes to get even temps throughout the mash....

RDWHWHB, your doin well!
Cheers!

 

[BumpyAZ]

I'm pretty sure the temp stratification was true. I calibrated the digital probe to typically read the same and at most one degree of separation with the kab thermometer prior to and during the brew sessions. I thought I had stirred pretty good prior to placing the kettle in the oven with minimal temp stratification but I didn't specifically mention that in the notes I took so I'll make sure I pay more attention to that on the next brew. I did preheat the oven and then turned it off when I placed the kettle in to start the mash because the lowest my oven goes is 170, not sure if that had any negative affect on temp stratification. Maybe I'll leave it on next time or try setting the oven in convection mode.

Doug, thanks for the info on mash out and SG calculations. One question, is the purpose of the mash out solely to inactivate the enzymes? I thought part of the reason two do it with BIAB was to thin the mash slighty allowing the wort to essentially "rinse" more sugars off of the grist?

Wilserbrewer, I'm a scientist so being very detailed oriented and anal about accurate and reproducible results is in my blood. Wish I could sake that for something as "simple" as beer, I'll keep trying. PS - I'm using your bags and they're awesome! From a fellow NJ home brewer, thanks for all your help!

 

[doug293cz]

Doug, thanks for the info on mash out and SG calculations. One question, is the purpose of the mash out solely to inactivate the enzymes? I thought part of the reason two do it with BIAB was to thin the mash slighty allowing the wort to essentially "rinse" more sugars off of the grist?

The slight drop in wort viscosity with a 20°F increase in temperature will have minimal effect on draining the bag. Even a 1.100 SG wort is at less than 30% of the sugar saturation level, so there is no solubility benefit to raising the temperature. When draining the bag after the mash, you are not rinsing sugar from the grain, but rather just removing the wort which has sugar already dissolved in it. If you do a sparge step, then you are doing a rinse operation. If you mash out by adding additional hot water to the mash, then you are diluting the overall wort, which means the wort retained in the grain will have less of the total sugar (same amount of wort will be retained, but it will be lower gravity), and more of the total sugar will be in the BK.

In cases where starch conversion is incomplete, a mash out can sometimes drive the conversion a little further by increasing the reaction & diffusion rates. This is more likely to occur more for coarser crushes vs. finer crushes because diffusion is more of a limitation for larger particles. The saccrification reaction rate increase is however competing with the enzyme denaturing reactions, and the denaturing reactions quickly win out. So, a better way to deal with incomplete conversion is to extend the mash time, and do more stirring (or recirculation) of the mash.

Brew on

 

[BumpyAZ]

doug, thanks for the thorough explanation!

 

[doug293cz]

doug, thanks for the thorough explanation!

You're welcome. Glad you found it useful.

Forgot to mention that another way to deal with incomplete mash conversion is to go to a finer crush, rather than longer mash time. This helps because one of the limiting processes in the mash is diffusion of water into the grain particles, and diffusion of sugar (and solubilized starch) back out of the of the particles. Care needs to be taken when doing fly sparging, as a finer crush will increase the likelihood of a stuck sparge. Batch sparging in a traditional MLT is less susceptible to stuck sparges, but still needs to be considered. When lautering by removing a bag from the BK (ie BIAB) or MLT, stuck sparges are a non-issue.

Brew on

 

[TheHopfather]

I don't bother with a mash out with my BIAB anymore. I did when I started, I've since found it just adds time to my brew day. I didn't see an appreciable increase in efficiency or any difference in the final product so I've since stopped doing it.

I typically mash in 8 degrees above my target mash temp and stir the grains until I've hit that temp. I then open the pot and check temps 2 more times during the mash, stirring until I've got a steady temp reading on the thermometer. The temps tend to jump around all over the place when you first start stirring. If I've lost a degree or two I'll apply heat to the pot to get it back up in range, I've brewed enough with my setup to know I'll lose a little less than a degree every 25 min or so. I've built a little jacket out of ReflectX for my pot/mash tun which helps maintain a more steady mash temp.