Another Attenuation Question

[BHive]

I know I'm just another homebrewer wondering why I keep ending up with higher than expected FG issues. Here's my process.

Brew in a bag.
I heat my full volume of water (8.6 gal) in kettle to 160f to get a strike temp of about 152f. I stir in my grain (13#). I then place a insulation jacket that I made around the kettle which tends to keep the temp pretty constant for an hour. It usually drops about 3-4 degrees in an hour so it slowly drops from 152 to about 148 in the course of a 1 hour mash.

This is a Belgian blonde recipe I have tried 3 times now. I am looking for semi-dry so I aim for the lower temp range.

I then pull out the grain bag, squeeze until I have 7.5 gals of wort. Bring to boil add hops and boil for an hour adding 12oz of table sugar at the end of boil.

Cool it down with my emersion chiller and pitch a slap pack of Wyeast #3787 Trappist. My OG has been between 1.064 and 1.068 for the 3 batches. It takes off bubbling and goes for several days. Then after 3-4 weeks when I rack to keg, I realize my FG is around 1.024.

BeerSmith thinks it should get as low as 1.012 so what is happening?

The beer still tastes pretty good actually, but it ends up around 4.75% instead of the intended 7%abv, and has a little more body than intended due to the unfermented sugars that are still there.

 

[cswis86]

I think you're focusing too much on your mash and not enough on fermentation. I think your mash is fine and should be getting decent conversion. I'd focus on making a yeast starter to pitch the appropriate amount of yeast and maybe add some yeast nutrient. It sounds like you're only pitching one smack pack into 7.5 gallons of wort which is not nearly enough. A 2-3L starter is probably what you should be using. Also consider adding pure O2 to your wort before you pitch the yeast to ensure you have adequate levels of oxygen for the yeast to grow.

 

[raysmithtx]

How are you taking your gravity readings? If you are using a refractometer then the readings will always be off since any alcohol will cause the reading to be to high. If you are using a hydrometer then disregard.

 

[beergolf]

I like 3787 a lot, so I have used it many times.

First thing I would suggest. Make a starter instead of just one smack pack. You are underpitching. Aerate very well before you oitch. Second thing you could try is to add the sugar after a few days of fermentation. This lets the yeast munch on the wort and then it will get desert when you add the sugar. Third thing is try extending you mash past an hour. Giving it a little longer may help get the FG down lower. Another thing. 3787 is famous for taking a long time to fully finish. It will fool you when it takes off like crazy and then slows down. But often if treated right it will tick off more points. Lastly, temp control during fermentation. I like to start 3787 in the mid 60's, hold it there for several days and then slowly ramp the temp up to the mid 70's. This will help the yeast finish out. 3787 is a yeast that does not like to be cooled down during fermentation. Often what happens is the yeast produces heat when it is actively fermenting, then it cools down when fermentation slows down. So if you can keep the temp from dropping after fermentation slows, that will help also. It should easily get down to 1.012.

edit: good call on the refractometer.

 

[BHive]

How are you taking your gravity readings? If you are using a refractometer then the readings will always be off since any alcohol will cause the reading to be to high. If you are using a hydrometer then disregard.

Interesting. I did not consider that at all. So how do I adjust my reading to account for alcohol?

 

[BHive]

I like 3787 a lot, so I have used it many times.

First thing I would suggest. Make a starter instead of just one smack pack. You are underpitching. Aerate very well before you oitch. Second thing you could try is to add the sugar after a few days of fermentation. This lets the yeast munch on the wort and then it will get desert when you add the sugar. Third thing is try extending you mash past an hour. Giving it a little longer may help get the FG down lower. Another thing. 3787 is famous for taking a long time to fully finish. It will fool you when it takes off like crazy and then slows down. But often if treated right it will tick off more points. Lastly, temp control during fermentation. I like to start 3787 in the mid 60's, hold it there for several days and then slowly ramp the temp up to the mid 70's. This will help the yeast finish out. 3787 is a yeast that does not like to be cooled down during fermentation. Often what happens is the yeast produces heat when it is actively fermenting, then it cools down when fermentation slows down. So if you can keep the temp from dropping after fermentation slows, that will help also. It should easily get down to 1.012.
.

This is all great advice, thanks. I'll use a starter next time. I've made sure the smack packs were fresh so I thought with the nutrient inside it would be adequate. Also, I will try a longer mash. Maybe 90 min.

 

[jurgenph]

Interesting. I did not consider that at all. So how do I adjust my reading to account for alcohol?

assuming that you used a refractometer to make both your OG and FG reading.

you don't adjust it, use a calculator.

i use an app called brixcalc on my phone, but there are online versions as well.

plugging in your numbers show me that your FG have been in betweeen : 0.997 and 1.0 SG that's pretty damn dry


J.

 

[beergolf]

Refractometer... That is your issue.

But you still need to do starters in the future.

 

[BHive]

assuming that you used a refractometer to make both your OG and FG reading.

you don't adjust it, use a calculator.

i use an app called brixcalc on my phone, but there are online versions as well.

plugging in your numbers show me that your FG have been in betweeen : 0.997 and 1.0 SG that's pretty damn dry


J.

I just attempted some online calculations also. Using a Gravity to Brix scale I determined my original brix was 15.65 (1.064). And my current (after fermentation) Brix was calculated as 7.06 (1.006). That's obviously lower than I even intended. Calculating the abv then gives me around 7.5%abv.

I tasted it last night and it didn't taste terribly dry. And there was a slight residual sweetness as well, which almost makes these calculations seem off to me, but hey... the computer is smarter than I'll ever be.

 

[BHive]

But I do feel smarter after every homebrewtalk consultation.

 

[chickypad]

If you're questioning the calculation then take a hydrometer reading. I've found Sean Terrill's calculator to be quite accurate. Looks like his site is down right now but Brewer's friend uses his equation and also explains how to get your wort correction factor.

 

[raysmithtx]

If you're questioning the calculation then take a hydrometer reading. I've found Sean Terrill's calculator to be quite accurate. Looks like his site is down right now but Brewer's friend uses his equation and also explains how to get your wort correction factor.

Yep. That's the one I use. I have tested it against my hydrometer readings and it's really close. I don't care that much about my F.G. but like knowing when the fermentation is done.

 

[GoeHaarden]

I just wanted to get some clarification on this topic, as I too have had this "attenuation problem" with all of my all-grain batches stalling at about 1.025-1.030. However, when using the recommended brix calculators in this thread I hit my gravities.

So, do most of you use a calculation when using a refractometer? I've doubled checked some of my readings with a hyrdometer and they are very close. I've never had this problem with any extract or partial-mash batches. Just curious why the F.G. doesn't drop in my all-grain batches like my other methods? I'm confused and frustrated...have tried to eliminate all variables in by brewing process, and my batches still "stall" and don't really taste all that great.

 

[chickypad]

I just wanted to get some clarification on this topic, as I too have had this "attenuation problem" with all of my all-grain batches stalling at about 1.025-1.030. However, when using the recommended brix calculators in this thread I hit my gravities.

So, do most of you use a calculation when using a refractometer? I've doubled checked some of my readings with a hyrdometer and they are very close. I've never had this problem with any extract or partial-mash batches. Just curious why the F.G. doesn't drop in my all-grain batches like my other methods? I'm confused and frustrated...have tried to eliminate all variables in by brewing process, and my batches still "stall" and don't really taste all that great.

I'm a little confused by your post. It sounds like you were making the same measurement error, using uncorrected refractometer readings after fermentation, but when you calculate properly you hit your intended gravities. It's not a problem with your batches, it's a problem with your measurements. You have to use the calculations if using a refractometer in the presence of alcohol. Or just use your hydrometer after fermentation.

 

[Morrey]

Chickypad makes a good point about hydrometer use during or post fermentation. I use a refractometer for readings prior to pitching yeast. I like the convenience of a refractometer and can sample a few drops of wort during a boil for a quick gravity check.

However the convenience ends once alcohol starts being created. Alcohol skews readings meaning I avoid the refractometer later on in the process. I then employ the use of a hydrometer so I end up using two separate instruments in the brewing process. You can use a conversion chart with a refractometer, but it is one more step I personally choose to avoid.

 

[GoeHaarden]

I'm a little confused by your post. It sounds like you were making the same measurement error, using uncorrected refractometer readings after fermentation, but when you calculate properly you hit your intended gravities. It's not a problem with your batches, it's a problem with your measurements. You have to use the calculations if using a refractometer in the presence of alcohol. Or just use your hydrometer after fermentation.

Ah hah! This clarifies everything...thanks! I never realized this and now that I think about it, I only started using a refractometer when I started all-grain. Just took a hydro reading of one fermenting and I nailed my F.G.