Missed OG, can someone explain this

Brewed today, 1st all grain BIAB. Efficiency not what I hoped for. Crush probably wasn't fine enough but had LHBS mill grains twice.

Anyway pre boil volulme was on but my gravity was 1.042 (estimated 1.045 beersmith) so I used BS2 calculator to add light DME to the wort to hit my pre boil gravity. After the boil my volumes were @ 5 gallons in the fermenter, just where it should be. I measured the OG and it was 1.055 (BS estimated 1.060).

What I don't understand is if my pre boil and post boil volumes were on and my pre boil gravity was where it was supposed to be how could I miss the OG?

The one caveat is I didn't take a gravity measurement after I added the DME. Maybe I should have done that to make sure I added enough.

Could I pasteurize some more light DME bring it up 5 points or will this affect the flavor?

 

Do you know of any experiments that have tested how far off the correction can be?

 

Thanks good to know for the future. Cool the sample before the refractometer.

Cheers

 

For biab, you should mash for 90 mins. 3 vessel system usually calls for 60 mins, but then lauter and sparge adds another 30 mins or so at the temp.


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Stoive87 you cannot and should not tell people that biab requires a longer mash. That is totally inaccurate. A number of folks on here have proven that conversion is actually an incredibly fast process completed in 5-10 minutes. The key to getting conversion this fast is super finely milled grist. 90 minutes is really more something you might consider with a traditional mash tun set up. The longer mash time allows for the larger particles to be more thoroughly wetted. Even then 90 min seems totally unnecessary in order to increase efficiency.

 

I mashed for 75 minutes just because that's what BS said to do. I didn't mash out or sparge. I think my issue was the grain crush. The LHBS milled it twice but looking at the grain it could have been milled more in my opinion. Guess it's time to buy a mill. But this wasn't about efficiency. I was more perplexed with missing my gravity give the calculations and volumes. Guess brewing isn't an exact science.

 

It actually is a pretty exact science... but you need to know your system and all the variables.
I'm going to guess that your addition of DME did not produce the results you were expecting, and since you didn't measure, we will never know.
Did you take good notes on boil-off etc?
Entering the exact equipment variables is super important in BS.
The other variables are water profile and grain crush.
Non-variables, but things that will throw you off are thermometer and volumes measurements. Are you sure they are accurate?
Get a couple more brews under your belt and I'll bet you will see better results.

 

I'm getting my info from the guy who invented biab in Australia. Basic brewing did a podcast about it here: http://traffic.libsyn.com/basicbrewing/bbr04-24-14biablegacy.mp3

Granted he did say that you shouldn't mill the grain more than usual for other reasons.

Also braukaiser did an experiment where the iodine test was negative, but the gravity continued to rise throughout the mash: http://braukaiser.com/blog/blog/2011/03/04/conversion-progress-in-a-single-infusion-mash/

I'd love to see evidence to the contrary. I know when I've done brew in a bag with only 60 minutes and no mash out, I've been disappointed with my 60% efficiency.


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I've done brew in a bag with only 10 minutes and no mash out with 80% efficiency. The difference is nearly always the milling of the grain. Poor milling can be compemnsated for somewhat by mashing longer but there comes a point where it just doesn't help.

 

Cool, I tend to go down to 80-85 normally, since my hydrometer reads about 2-3 points high (autocorrection by temperature).