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Poor Attenuation? Low Efficiency? WTF Happened?

Here’s the recipe I brewed

6 Gal batch, All Grain, 60 min boil, 60 min mash

Fermentables:

2-row: 7.75 lbs
Marris Otter: 5lbs
Flaked Oats: 1.5 lbs
Chocolate Malt: 1.25 lbs
Vienna Malt: 1 lb
Roasted Barley: 1 lb
Crystal 120: 8 oz
Victory: 8 oz
Black Malt: 6 oz

Extras:
Lactose: .7 lbs @ 60 Min

Yeast: US-05, (2 packets)

When i enter this recipe into BrewToad, I get a target OG of 1.087. And when I brewed this beer, my OG, right before pitching was 1.085. So I’m thinking… cool, I should be good.

But after three weeks, I take a gravity reading and my FG is 1.032. Pretty damn high.

So here’s what I’m thinking happened, my OG should have been maybe 30 points higher to account for the unfermentable lactose. But in the end I got pretty poor mash efficiency which is why my OG was only 1.085 WITH the Lactose.

The reason this strikes me as odd is that I almost ALWAYS hit 70 - 74% efficiency with this setup. So it seems strange to me that I’d be so far off the mark.

Any thoughts?

Might be your mash temp. You didn’t mention what that was. I’d certainly mash on the low side with such a busy grain bill to try and get as fermentable a wort as possible, especially since you’re adding lactose. I also might mash for 90 minutes too. Got any water/wort pH issues? Did you pitch a MASSIVE starter? Have you tried rousing your yeast a little? Just a few thoughts…

Did you check you PH? All of those dark roasted grains could have brought your PH pretty low.

I bet it is a combination of high mash temperature and the lactose. If you want a high gravity beer to attenuate well, you probably shouldn’t add any lactose.

[quote=“Chris-P”]

When i enter this recipe into BrewToad, I get a target OG of 1.087. And when I brewed this beer, my OG, right before pitching was 1.085. So I’m thinking… cool, I should be good.

But after three weeks, I take a gravity reading and my FG is 1.032. Pretty damn high.

So here’s what I’m thinking happened, my OG should have been maybe 30 points higher to account for the unfermentable lactose. But in the end I got pretty poor mash efficiency which is why my OG was only 1.085 WITH the Lactose.

The reason this strikes me as odd is that I almost ALWAYS hit 70 - 74% efficiency with this setup. So it seems strange to me that I’d be so far off the mark.

Any thoughts?[/quote]

#1 The way I read it the whole recipe with “everything” should be 1.087 and you got 1.085.
Which seems entirely possible that only means 1-3% efficiency loss which is nothing.

#2 Two packets of US05 should be plenty and needs no massive starter as its dry yeast, but I may have pitched three packs or added the third 2-3 days into ferment along with nutrients if rising close to 1.100 like you did. So it is quite possible to end at 1.032. A. because of the amount of lactose and other unfermentable dextrins in the mix. B. The sugar density was just too much for the yeast pitch and they were destroyed/crippled initially or flocced out too early and/or simply gave up as you did hit around 60% attenuation and that is short of the 70-80% seen with US05 so it got most the way through and/or the remaining sugar/ SG was just unfermentable again.

#3 If I misread something in your SG estimation which if still dropped well under 70% from something I am not adding up in your statement than it is explainable as I know for myself anyways when I am seeking SG’s well over 1.060 I have to estimate around 65-75% instead of my typical 80-85% seen <1.060.

[quote=“ITsPossible”]
A. because of the amount of lactose and other unfermentable dextrins in the mix. B. [/quote]
Why would the amount of unfermentable sugars affect yeast’s ability to attenuate on fermentable sugar?

[quote=“ITsPossible”]

#3 If I misread something in your SG estimation which if still dropped well under 70% from something I am not adding up in your statement than it is explainable as I know for myself anyways when I am seeking SG’s well over 1.060 I have to estimate around 65-75% instead of my typical 80-85% seen <1.060.[/quote]

Actually, when I went back and did the math, I don’t think the lactose should have bumped up the gravity as much as I suspected. Lactose has 36 ppg. I added .7 lbs into 6 gallons. So that should have added roughly 5 gravity points to my OG. So I think the bigger issue I saw here was with attenuation. And I usually have very good success with US05. I guess I need to read up a bit on lactose.

I’m wondering if I could pitch some WLP090 to finish the job. Right now I’m at about 7% ABV. Thoughts?

US-05 is a great attenuator. Again I ask: What was your mash temperature?! Perhaps your mash thermometer is not properly calibrated. Or heck, maybe your hydrometer. Check all those things. Pitching more yeast will be of very limited benefit if at all at this point in the game.

1 Like

I mashed at 150 for 60 min. But I’m not sure what bearing that has on this topic. The main issue I see, at this point, is that my yeast didn’t attenuate down to where it should have. Yeah, maybe I could have gotten a little better efficiency by mashing longer, but I dont think that’s the principle issue.

Thoughts?

I think what Dave is getting at is that if your thermometer is off and you mashed at higher temps you would have a less fermentable wort which resulted in a higher FG, especially with that grain bill.

I mashed at 150 for 60 min. But I’m not sure what bearing that has on this topic. The main issue I see, at this point, is that my yeast didn’t attenuate down to where it should have. Yeah, maybe I could have gotten a little better efficiency by mashing longer, but I dont think that’s the principle issue.

Thoughts?[/quote]

You had almost 30% specialty grains and lactose and you wonder why you have a bad attenuation? Kinda seems like a no brainer.

I mashed at 150 for 60 min. But I’m not sure what bearing that has on this topic. The main issue I see, at this point, is that my yeast didn’t attenuate down to where it should have. Yeah, maybe I could have gotten a little better efficiency by mashing longer, but I dont think that’s the principle issue.

Thoughts?[/quote]

You had almost 30% specialty grains and lactose and you wonder why you have a bad attenuation? Kinda seems like a no brainer.[/quote]

I’m a fairly new brewer (brewing for about a year), so it’s not that obvious to me. Can you spell it out for me? Are you saying that the lactose and the specialty grains interfere with the yeast converting the sugars from the base malts?

speciality malts contain more complex sugars, some of which do not ferment.

Dark caramel and roasted malts like Crystal 80, Crystal 120, Special B, Chocolate Malt, and Roast Barley have a high proportion of unfermentable sugars due to the high degree of caramelization (or charring). The total soluble extract (percent by weight) of these malts is close to that of base malt, but just because it’s soluble does not mean it is fermentable. These sugars are only partially fermentable and contribute both a residual sweetness and higher FG to the finished beer.

oh and lactose A milk-based sugar that is not fully fermentable by beer yeast. Adds body and sweetness to sweet stouts.

You added a ton of non/lesser fermentable sugars. This is going to leave you will a high final gravity.

Lactose is 100% unfermentable sugar. Crystal malts vary in their fermentability but you can figure as a ballpark maybe 50% nonfermentable sugars. So… your recipe has a lot of sugar in it that beer yeast is not capable of fermenting.

I would still double-check the accuracy of your mash thermometer and your hydrometer. Hydrometer should read 1.000 in 60 F water. If it doesn’t, you need to make adjustments. Your mash thermometer should read close to 212 F in boiling water, or different depending on your elevation (e.g., in Denver the boiling point would be a bit different than at sea level). If your mash thermometer is reading too low, your mash temperature might have been quite high, like at 158 or 160 F then more unfermentable sugars are produced in the mash versus at lower temperatures of 147-150 F where more simple easily fermentable sugars are produced. All of these factors can make a lot of difference, especially if more than one factor is happening at the same time. So not only did the lactose hurt your attenuation, but also I bet either your hydrometer or your thermometer is a little bit off and made the problem even worse.

Thanks all for the education.

I will definitely double check my thermometers. Might be time to invest in a Thermapen or something I can use as a truly accurate yardstick against which i can judge all other thermometers.

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