[Pope of Dope]

Brewed a 6 gal batch of mostly fermentables: 7lbs Marris, 5lbs German Munich, mere ounces of crystal 40, carapils, and chocolate for color and body. I used a BIAB, I mashed in at 149f, I mashed out at 170f -- analogue thermometer in brew pot Spike kettle and checked with handheld digital.

OG = 1.070

I added two packets of Safale .05, dry and poured directly into fermenter. I fermented at 68f with temp control (I did not use yeast nutrient this time, I was out).

After ten days my gravity was 1.020. It remained unchanged. I thought it could be stuck so I made a larger sized starter with WLP004 Irish ale and dumped it in. This didn't help.

FG= 1.020

All measurements were taken with hydrometer and temperature was accounted for. You get what you get and you don't get upset, but with all of that .05 yeast, all the fermentables, the ideal temps, no real errors that I can think of, and then the attempt to clean it up further at the end with the starter, why didn't I get a lower FG?

[erockrph]

Is your hydrometer calibrated correctly? 1.070 OG seems a little high for 12ish pounds of grain, but if your hydrometer was reading a little high then something  like 1.065 > 1.015 would seem like a reasonable result.

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[Pope of Dope]

Hydrometer is calibrated. Yes it's a little high. I was aiming for 1.060

[chinaski]

Maybe your thermometer is off and the mash temp was higher than you think?

[Pope of Dope]

Improbable. One digital and the analogue thermometer is always spot on. It really is a mystery. I've been here before. While I love the ease and clean up of the BIAB, and I've had some excellent results, I become suspicious when failures happen. With this brew everything was spot on. It's a recipe I've made more than any other, my flagship IPA that I've made for over a decade.

On a positive note, it's all carbed up and in the keezer now. Had my first glass. It's still good.

[ynotbrusum]

In my experience BIAB only affected the starting gravity and not so much anything to do with the final gravity.  FG is more mash temp related - but at 149F and a mash out, it is an anomaly.  If it tastes good, then who cares, right?  Sorry for not adding much here, but that’s brewing!

[rburrelli]

I am beginning to think pH issues maybe or water source. Did you/do you measure pH of the mash? And what was the water source?

[stpug]

Beta content of the malt is the culprit. Aside from including some malt with large Beta content and exhausting the Beta, not much you could have done.

[Pope of Dope]

pH was just fine, water was adjusted and salts were added for proper mineral profile.

Beta content of the malt? You have my ears pricked. What does that mean exactly?

Beta amylase, but what I mean is how can one know the beta content of malt? I just buy at LHBS by the pound. Good Marris and Munich, is there someplace you are supposed to check for Beta content? 

[Big Monk]

pH was just fine, water was adjusted and salts were added for proper mineral profile.

Beta content of the malt? You have my ears pricked. What does that mean exactly?

Beta amylase, but what I mean is how can one know the beta content of malt? I just buy at LHBS by the pound. Good Marris and Munich, is there someplace you are supposed to check for Beta content?

My big concern would be how long did you mash at 149 F? What was your grist ratio? How fine do you crush?

Beta activity is reduced as you approach 149 F, which is the main reason most people have to mash > 60 minutes at that temp to get adequate attenuation. The water to grist ratio also effects beta activity, with more dilute mashes shortening the timing and potency of beta amylase. Lastly, there seems to be a correlation between crush and gelatinization temperature, with finer crushes raising that temperature and vice-versa for coarser crushes.

[ynotbrusum]

pH was just fine, water was adjusted and salts were added for proper mineral profile.

Beta content of the malt? You have my ears pricked. What does that mean exactly?

Beta amylase, but what I mean is how can one know the beta content of malt? I just buy at LHBS by the pound. Good Marris and Munich, is there someplace you are supposed to check for Beta content?

My big concern would be how long did you mash at 149 F? What was your grist ratio? How fine do you crush?

Beta activity is reduced as you approach 149 F, which is the main reason most people have to mash > 60 minutes at that temp to get adequate attenuation. The water to grist ratio also effects beta activity, with more dilute mashes shortening the timing and potency of beta amylase. Lastly, there seems to be a correlation between crush and gelatinization temperature, with finer crushes raising that temperature and vice-versa for coarser crushes.

For clarity are you saying that if you have a dilute grist ratio (thinner mash common in BIAB techniques), the beta amylase activity is shortened (it peters out more quickly) and is less effective?  Or do you mean that the beta amylase activity more quickly reacts and converts (or doesn't), but has less potency overall in the dilute mash of a BIAB mash?  Also, would lengthening the mash time, or stirring or recirculation of the mash recover some of the effects of same?

[Big Monk]

pH was just fine, water was adjusted and salts were added for proper mineral profile.

Beta content of the malt? You have my ears pricked. What does that mean exactly?

Beta amylase, but what I mean is how can one know the beta content of malt? I just buy at LHBS by the pound. Good Marris and Munich, is there someplace you are supposed to check for Beta content?

My big concern would be how long did you mash at 149 F? What was your grist ratio? How fine do you crush?

Beta activity is reduced as you approach 149 F, which is the main reason most people have to mash > 60 minutes at that temp to get adequate attenuation. The water to grist ratio also effects beta activity, with more dilute mashes shortening the timing and potency of beta amylase. Lastly, there seems to be a correlation between crush and gelatinization temperature, with finer crushes raising that temperature and vice-versa for coarser crushes.

For clarity are you saying that if you have a dilute grist ratio (thinner mash common in BIAB techniques), the beta amylase activity is shortened (it peters out more quickly) and is less effective?  Or do you mean that the beta amylase activity more quickly reacts and converts (or doesn't), but has less potency overall in the dilute mash of a BIAB mash?  Also, would lengthening the mash time, or stirring or recirculation of the mash recover some of the effects of same?

It's both. Beta Amylase activity is already greatly diminished at temperatures around 149 F, as the half life of the enzyme at those temperatures is short. In a more dilute mash, Beta Amylase will work quickly but also denature quickly. Part of the reason that mashing low and long works is due to this phenomenon. In order to get decent attenuation from a single infusion mash around the 148-149 F mark, you need to extend mash time.

Another issue is gelatinization. If you are working with a malt that, due to seasonal variation, etc., has a high gelatinization temperature, you are forced to mash higher to allow the malt to gelatinize and starches to go into solution. This obviously puts you at a disadvantage because in a perfect world you would ideally want to mash lower, as the lions share of beta activity happens around 144 F.

There are ways around this though but it seems outside the scope of this particular thread. lupulus has been championing a "coast down" or isothermal beta rest whereby you mash in at above the gelatinization temperature and let the mash naturally cool down to a more active beta temperature. Probably wouldn't work as well for cooler brewers though.

Also, crush can play a role in gelatinization as well. There seems to be a correlation between coarseness of crush and gelatinization.

There is so much good info out there. It's just a matter of troubleshooting the specific issue and applying the science to it.

[ynotbrusum]

So it sounds like a longer, lower initial temp range mash coupled with recirc or periodic stirring and then adding a mash out would likely solve most of the problems, as long as you are able to raise the mash into the alpha range at the endpoint of the mashing and perhaps proceed to mash out for full range exposure of the mash?

I am thinking a Hochkurz type approach - I used to have it in my head as 144 for 30, 162 for 30 and 172 for 10.

[stpug]

pH was just fine, water was adjusted and salts were added for proper mineral profile.

Beta content of the malt? You have my ears pricked. What does that mean exactly?

Beta amylase, but what I mean is how can one know the beta content of malt? I just buy at LHBS by the pound. Good Marris and Munich, is there someplace you are supposed to check for Beta content?

Diastatic power of malt identifies it's ability to convert starch to sugar.  What it doesn't indicate is the proportion of beta (130-150F) to alpha (140-170F) enzymes.  Sometimes alpha is indicated in malt spec sheets, but not always, and you may be able to determine the level of beta available from that value.  When neither level is known then you need to consider the malt itself and how they are traditionally malted in their respective countries.

Maris Otter = base malt that can usually self-covert, but not much extra diastatic power for other non-diastatic malts.  Well kilned malt to develop the biscuity character.  Higher temp kilning reduces the distatic power to a level that's sufficient for self-conversion.  Higher temp kilning denatures beta quickly, whereas alpha is more stable at the kilning temps.

German Munich = very similar in nature to maris otter with the exception that Munich I (i.e. Light Munich) retains more diastatic power and likely more beta and alpha.  Dark munich (Munich II) contains about enough diastatic power for self-conversion, but not much else.  Also, the dark variety is kilned for longer and those higher temps that denature beta more quickly.  Dark munich will contain lower levels of beta than light munich.

crystal 40 = non-diastatic (i.e. no alpha, no beta)

carapils = non-diastatic

chocolate malt = non-diastatic

Given the malt makeup of your brew, it would leave me to believe that you simply lacked enough beta for producing a highly-fermentable wort.  Short of using a STA1 yeast strain (I wouldn't), or adding glucoamylase enzymes (I wouldn't) to your existing beer then I would simply enjoy what you produced and adjust on the next batch.

Aside from the knowledge gained from this, and how it might be mitigated or avoided next time, you've gained knowledge on how you can achieve a lower-attenuating wort with ingredient choice.  This kind of knowledge is wonderful for those times you'd NOT like to attenuate to 80%+.

Hope this helps.

[chinaski]

It's a recipe I've made more than any other, my flagship IPA that I've made for over a decade.

How would beta amylase concentration explain this?  I once heard a very good pro-brewer state that conversion is nearly instantaneous for all practical purposes; which led me to think that there are other flavor contributions from one-hour or more mash rests.