Poor attenuation after poor attenuation

[malaeum]

I just started doing AG on my own, brewed a few batches with friends over the years but I've finally made the plunge and I am stuck with poor attenuation rates. In regards to the suggestions on this forum:

• I aerate my wort for ~15 minutes right before pitching and for ~10 minutes directly after pitching with an aquarium pump and aeration stone.
  
• I mash at 150-154. I use a thermapen, its dead on calibration for boiling.
  
• I use a minifridge wired up with an STC-1000 for temperature control. I also have a fermometer sticker on the side of my corny I ferment in and it is in great agreement with where I have my thermostat set at. Usually start around 66 and end around 72 (depends on the yeast strain).
  
• I make a 1.5L yeast starter, starting from Wyeast packets and aerate the starter as often as possible (usually 30+ times over 2 days).
  
• According to my water report, I have medium hard water which sounds about right.
  
• Mash pH has been measured from 5.1 to 5.7 (usually around 5.3 on average).
  
• I've been adding 1/2 tsp. of yeast nutrient in during the last 10 minutes of the boil.

Some examples of what I would call extreme underattenuation:

Ale with Ginger:

Yeast=Wyeast 1214
OG=1.040
FG=1.017
Time=3+ weeks in primary
AT=57.7% [74-78 expected]​

Toasted Coconut Porter:

Yeast=Wyeast 1318
OG=1.058
FG=1.030
Time=2.5 weeks in primary, no change over the past 5 days
AT=51.7% [71-75 expected]​

So far I am at a loss for what could be wrong. My starters look healthy and of decent size. I could move to oxygen, but seeing as how in the past when I brewed with friends we just shook it up and never ran into these problems, I am not so sure that is my problem...

I am new to the hobby and it might very well be patience is all that is needed, but having read plenty of other peoples experiences, I feel like there is something else I am missing. So far I have only had one beer hit the desired attenuation numbers (out of three), and for that one I did not create a starter, it was 1.067 OG and I simply pitched two packets of yeast. I really am starting to wonder if making a starter is worth it (with my process at least.)

 

[Hex23]

I don't think patience is the issue. Those beers should likely attenuate within that timeframe. It might be worth trying a forced ferment test to see where the issue lies. You might even be able to pull off some of your fermenting beer and try to force ferment that?

 

[grathan]

What was the porter recipe?

 

[malaeum]

Thanks for the suggestion. I will be making a starter for another batch being brewed this weekend. I will grab some of the yeast from that and give both of these "stuck" batches a forced fermentation test to see what happens. I'm guessing that they ferment down some more. If that is the case, is moving from aeration to oxygenation the first step? I also think I will probably be moving away from my aerated starter to a stir-plate setup; would that make a big difference?

Thanks again!

 

[Hex23]

Thanks for the suggestion. I will be making a starter for another batch being brewed this weekend. I will grab some of the yeast from that and give both of these "stuck" batches a forced fermentation test to see what happens. I'm guessing that they ferment down some more. If that is the case, is moving from aeration to oxygenation the first step? I also think I will probably be moving away from my aerated starter to a stir-plate setup; would that make a big difference?

Thanks again!

It seems like you're doing alot of things right. I tend to doubt that going from intermittently stirred to stirplate starter is the answer. I doubt you're under-pitching by that much. And like you said, your brews with friends attenuated OK with shaking for oxygenation. I think studies show that shaking is a pretty good way to oxygenate. You won't reach the O2 levels you can with pure O2, but most people don't have attenuation problems with just shaking the carboy. You're also talking about some pretty significant attenuation problem.

How are you measuring OG/FG? Hydrometer or refractometer with correction?

 

[Face Eater]

I think recipes may help here to figure out what is going on. 150 to 154 seems like a good mashing temp for attenuation but also depends on what is in the recipie. Too many unfermentables? Everything else process wise seems good. What was the viability of the yeast (dates).

 

[malaeum]

I am measuring with a refractometer. I have a hydrometer but really don't have a great way to pull samples of that size, though it is worth giving a shot just to see how well they correlate with my refractometer (on brew days it seems to be ±0.002 of the hydrometer).

As for the recipes, I was thinking the same thing, and I will fully admit I'm a novice here, but I don't think I have very much unfermentables going in.

For the Ale with Ginger, the grain bill was:

• 5 lbs. 2-Row
• 2 lbs. Crystal Malt (10° L)
• 1 lb. Munich Malt (10° L)
• 1 lb. Flaked Oats

And for the Porter:

• 10 lbs. Pale Ale Malt
• 1 lb. Chocolate Malt
• 10 oz. Crystal Malt (90° L)
• 12 oz. Flaked Oats

For the Ginger beer, the yeast was less than a month old (around 3 weeks) and for the porter it was coming up on 2 months old.

Let me know if you need more info than that. For what kit is worth, both of these are recipe its bought online. I wanted to be able to start with known good recipes while I worked out the bugs in my process before I ran off getting creative on my own.

Thanks again!

 

[Hex23]

I assume you are correcting your FG values if you're taking them with the refractometer. You can't really use a refractometer to measure FG due to the alcohol interfering. Even correction methods can be inaccurate. Do the beers taste underattenuated?

 

[KGB09]

I assume you are correcting your FG values if you're taking them with the refractometer. You can't really use a refractometer to measure FG due to the alcohol interfering. Even correction methods can be inaccurate. Do the beers taste underattenuated?

+1 to this. Use the hydrometer. Buy a cheep turkey baster to get your sample out.

 

[grathan]

You can even poor some warm finished beer into the hydrometer jar. Just spin off carb bubbles or even let sit overnight. Just to double check the refractometer calculations.

 

[crushingblackdoom]

Just a thought, but how's your crush? Do you grind your own with a personal mill, or lhbs does the crushing? That makes a big difference in AG brewing.
Also, maybe try mashing longer.

Try overnight mashing and sparge/boil first thing in the morning! Makes for very attenuated dry crisp finish for me. However I do this with respect to the recipe, ingredients and brew plan.
Just my two cents.
Good luck!

 

[malaeum]

I assume you are correcting your FG values if you're taking them with the refractometer. You can't really use a refractometer to measure FG due to the alcohol interfering. Even correction methods can be inaccurate. Do the beers taste underattenuated?

You see, that would be a poor assumption with an amateur brewer such as myself. I think you might very well have hit the nail on the head. I read about correcting my refractometer a few months ago before I even bought it. I tested it out on unfermented wort and found the correction to be not worth my time (it was less than 1 point). Now I see that it is FAR more important for FG readings. I will have to remeasure my gravities tonight when I get home, but if I use an image of the scale in my refractomerter to translate my FGs to Brix and use this calculator I see that my 1.030 FG equates to 1.0137 and my 1.017 FG equates to 1.007, attenuations of 76.4% and 82.5% respectively. Now this is all calculated quickly from estimates so I will be sure to re-check these numbers when I get home and read up on this, but it seems that I am doing quite well!

I feel like an idiot, but honestly, I'd rather be wrong than have bad beer!

Just for the record I have the malt premilled when I buy my recipe kit but I brew within a month of receiving it. My mash efficiencies are ~80%. Would crush effect the types of sugars produced at a given temp/pH? I could see how it would effect extraction efficiency but I would be surprised if it changed the enzymes products.

 

[Hex23]

I feel like an idiot, but honestly, I'd rather be wrong than have bad beer!

Nah, don't feel bad, it was clear to me that you had a good working knowledge of the brewing process by the questions you were asking. Your numbers were so far off normal I was having a hard time believing it was in the way you were brewing. Many people assume that you can use a refractometer to measure FG. When I first read that you can't directly, I was disappointed and put off buying one. Then I bought one for checking the mashing process. I still don't use it for FG measurements because of the estimation inaccuracy. I'm even still trying to wrap my head around some pre-fermentation correction issues I've seen.

 

[malaeum]

Following up, the gravities measured by hydrometer for each are as follows:

Ginger Ale, FG=1.009, Attenuation=77.5%
Porter, FG=1.015, Attenuation=74.5%

Looks like I was doing great all along. Thank you guys very much for all of the suggestions and for helping me solve my (apparent) poor attenuation.

Prost!