Decoction mash question.

[Matt3989]

Okay, so on Sunday I did my first decoction mash. It was a pumpkin rye ale, I first did a saccrification rest at 120 for 45 minutes, then decoted 3 gallons (the mash had 15lbs of grain plus 6 pounds pumpkin/butternut squash in it). Boiled that 3 gallons and added it back to the mash, per my beersmith mash profile, only that only raised the temp to 144 (due to the massive heat sink that is pumpkin I'm assuming). So I decoted a second 3 gallons and boiled that, then added it back in which got me to my target temp of 154.

After boiling, and cooling down to about 61dF, I pitched a smack pack of 1099, the smack pack hadn't inflated like a normal one, and this was the first time in a long time I didn't have time to make a starter... (The gravity was 6 gallons at 1.057, I planned on the pumpkin hurting my overall efficiency). I have had no fermentation activity for 2 days, keeping it in a freezer at 63dF, so I took it out and warmed it up to 70, and shook it up a few times, still no activity 12 hours later.

So, for those still with me, here's my question, in a decoction mash, does boiling the liquid I decoted off kill the enzymes in it? Or do they start working again once the temp returns to their optimal range? My concern is that by boiling 3 gallons twice, I stopped enzyme activity and was left with a very unfermentable wort. My iodine test did show that full starch conversion happened.

So, just bad yeast? Or is my problem more serious?

 

[TIPA0303]

If you got conversion via the iodine test, then your enzymes should have been fine.

It's prob your yeast in my opinion.

 

[thereferee2]

Okay, so on Sunday I did my first decoction mash. It was a pumpkin rye ale, I first did a saccrification rest at 120 for 45 minutes, then decoted 3 gallons (the mash had 15lbs of grain plus 6 pounds pumpkin/butternut squash in it). Boiled that 3 gallons and added it back to the mash, per my beersmith mash profile, only that only raised the temp to 144 (due to the massive heat sink that is pumpkin I'm assuming). So I decoted a second 3 gallons and boiled that, then added it back in which got me to my target temp of 154.

After boiling, and cooling down to about 61dF, I pitched a smack pack of 1099, the smack pack hadn't inflated like a normal one, and this was the first time in a long time I didn't have time to make a starter... (The gravity was 6 gallons at 1.057, I planned on the pumpkin hurting my overall efficiency). I have had no fermentation activity for 2 days, keeping it in a freezer at 63dF, so I took it out and warmed it up to 70, and shook it up a few times, still no activity 12 hours later.

So, for those still with me, here's my question, in a decoction mash, does boiling the liquid I decoted off kill the enzymes in it? Or do they start working again once the temp returns to their optimal range? My concern is that by boiling 3 gallons twice, I stopped enzyme activity and was left with a very unfermentable wort. My iodine test did show that full starch conversion happened.

So, just bad yeast? Or is my problem more serious?

Definetly sounds like yeast problem!

 

[rklinck]

When you decoct, you are supposed to take the thick part of the mash (e.g., the grain). The vast majority of the liquid should remain in the mash tun. Did you pull primarily liquid for your decoction?

If you decocted the liquid, you most likely denatured the enzymes. A decoction works because you leave behind the liquid where the majority of the enzymes are.

 

[Matt3989]

When you decoct, you are supposed to take the thick part of the mash (e.g., the grain). The vast majority of the liquid should remain in the mash tun. Did you pull primarily liquid for your decoction?

If you decocted the liquid, you most likely denatured the enzymes. A decoction works because you leave behind the liquid where the majority of the enzymes are.

That's what I was afraid of, I thought I read about "thick" decoctions and "thin" decoctions, the difference being whether or not you pull out grain with it. I should've researched more before I tried this, but I've been busy... Oh well, guess I'll just have to brew this again haha.

Thanks.

 

[Molybedenum]

120 is usually the protein rest, where the sacc rest is in the 145-158 range (depending on how fermentable you want your wort).

Most mashes don't need a super long protein rest, if any. You might want to consider recalculating your mash method in any case.

 

[Yooper]

Is the 120 mash temp at 45 minutes a typo? You said "saccrification rest at 120". Saccrification won't happen at 120. You need to be at least at 140 (preferably higher than that even) for saccrification. You did a lengthy protein rest. And as was mentioned, you pull grain and only enough liquid to avoid scorching the grain, for a decoction. You bring the grain in the decoction up to conversion temperature and hold it a bit, so it will convert, then bring it to a boil for the next temperature step. You don't bring it right to a boil because then it won't convert.

By boiling the liquor, you would denature the enzymes. You only pull liquid for the "mash out" decoction, because that's when you want to denature the enzymes.

That may or may not be why it's not fermenting, but probably not. It sounds like a yeast issue as well.

 

[Matt3989]

The 120 was just a protein rest, I read a blog that recommended it when mashing with pumpkin. It was a hastily thrown together brew day, so that's definitely my first mistake, but I'll know for next time.

The 120dF liquid was actually extremely tough to drain from the mash tun, and 154 liquid was very easy, so I'm not sure the 120 was actually beneficial at all.

I had some yeast left from a large starter that I pitched into the wort before work this morning. I know that yeast is active and healthy, so I'll see if there's any fermentation after work today... It wasn't the same strain, but I was worried that oxygenated wort sitting around for 3 days would become cardboard without the aerobic phase of the yeast.

I'll let you guys know if I do get any fermentation, or if my final gravity will turn out to be 1.057, hopefully some one can learn from my mistakes haha.

 

[Matt3989]

Okay, so after getting home from work (roughly 12 hours after pitching fresh yeast), there is a small krausen on my beer, not really active fermentation like I'm used to seeing, but something is better than nothing.

Still, I'm thinking this will end up having lots of unfermentables in it and finish way to high.

 

[signpost]

How long did it sit at 154°F after you finally got it there? If I'm not mistaken, lack of conversion would show in your gravity reading. So, if the 1.057 was at or near your expected OG, then you should be fine. I don't think unconverted starches contribute to the gravity of the wort, because I don't think they completely dissolve. I may have accidentally made that up, but it makes sense to me.

And the reason for your fermentation lag could be a combination of things, but probably is not related at all to your decoction issues. How fresh was the smackpack? If it wasn't very fresh, that would explain why it didn't inflate like others you've had. And then pitching it directly into 6 gallons of 1.057 wort meant that the yeast had to grow a lot before it could really get busy with fermenting.

 

[Matt3989]

It sat at 154 for 45 minutes, I believe I probably got most of the conversion necessary when I was at the lower temps, before I denatured too many of the enzymes. The gravity reading was a little low, but I chalked that up working with a big mash, plus the 6 pounds of vegetable matter (the pumpkins/ butternut squash).

I believe my (main) problem was in the yeast. The smack pack was 5 months old. I pitched fresh yeast after waiting 2 days and seeing no activity at all. Within 12 hours there was a healthy krausen, within 18 hours I was waking up in the middle of the night to a whistling sound, then rushing to add a blow off tube.

So hopefully, my mistakes during the mash, and letting the oxygenated wort sit around for 2 days, things still turn out okay.

 

[signpost]

Yeah, if you only missed your OG by a little bit, then you should be fine. 5 month old yeast without a starter was definitely the culprit. It may have eventually fermented the whole batch, but that level of under-pitching would likely have caused off flavors.

So, pitching new yeast was a good choice and your beer should turn out just fine.

 

[retheisen]

in a decoction mash, does boiling the liquid I decoted off kill the enzymes in it? Or do they start working again once the temp returns to their optimal range? My concern is that by boiling 3 gallons twice, I stopped enzyme activity and was left with a very unfermentable wort. My iodine test did show that full starch conversion happened. So, just bad yeast? Or is my problem more serious?

The amylase enzymes are released into the liquid early in the mash process. If you took your decoction primarily from the liquid portion the most of your enzymes may very well have been denatured by the heat of the boil. Ideally your decoction media will be primarily the mash solids (you want to heat gelatinize and brown the starchy stuff) to get color and interesting flavors from the decoction. Once the enzymes are denatured they do not reform once they return to their ideal working temps.