Final gravity, what happens to the yeast?

[ElJayEm]

Hi All,

A bit of background:

Having played around with kits in my youth I've returned to brewing and have just brewed my first all grain batches: Jim Line's London Pride Clone. I decided to work on the same recipe for the first few brews to hopefully make it easier for me to refine my technique and learn what's going on while keeping a lot of variables constant. I've scaled the recipe down to 1 gallon as follows:

700g Marris otter
50g crystal
50g demerara sugar

6g fuggles 12g Golding's at start of boil
3g Goldings at end of boil to steep for 15minutes
2g Golding's dry hopped for seven days, added after seven days of fermenting
Safale s04 yeast

Mash for 1:30 in cooler, strike at 70c
Boil 1:30

The first batch was bottled last weekend. I don't think I sparged for long enough and ended up with an OG of 1.032. This fermented down to 1.004 by the time I added the dry hops at day seven. The gravity didn't change for the next seven days before I primed and bottled giving me an FG of 1.004

The second batch was brewed a week later and I used a longer sparge and more sparge water. This gave me an OG of 1.042 which sounded more promising ( the recipe suggested 1.040). After a week in the fermenter I took a gravity reading when I added the dry hops. It was 1.010. I checked again two days later and it hasn't changed.

This has raised a few questions and I was wondering if anyone could help me out as I don't really understand exaclty what is going on.

1. Is 1.010 too high to bottle if it remains at this point for the rest of the week? The chart here: http://homebrewmanual.com/beer-gravity-chart/ would suggest that it's actually about right for an English bitter and I wouldn't have worried, but my hydrometer packaging says in bold writing not to bottle above 1.006 or 'bottles will burst!'. It even has a black line at 1.006 to make the point.

2. Why do yeasts stop fermenting? I thought it was because they ran out of fermentable sugar or because their environment was too alcoholic. If the environment is too alcoholic, why do they start fermenting again when priming sugar is introduced? If they have run out of sugar, how can two batches with the same recipe run out of sugar at different points?

These are probably stupid questions and I'm missing something obvious but I can't get my head around it.

Thanks

 

[pvpeacock]

There are many variables which go into what your final gravity will be including mash temperature and type of yeast you are using. As a result, there is no hard a fast number above or below which you can safely bottle. The key is confirming that you have reached final gravity -- no change in gravity over the span of a few days. In addition. 1.010 is in the reasonable range for a final gravity reading. I had many beers finish at 1.012 particularly when using extract.

 

[chickypad]

That sounds like it's a warning for winemakers maybe? Makes no sense for beer.

 

[Nickyssix]

1.010 is a decent FG ,.. but those yeasties are unpredictable - who knows what theyre going to do next. Slightly different everytime.

 

[Puddlethumper]

These are probably stupid questions and I'm missing something obvious but I can't get my head around it.

There are many variables which go into what your final gravity will be including mash temperature and type of yeast you are using. As a result, there is no hard a fast number above or below which you can safely bottle. The key is confirming that you have reached final gravity -- no change in gravity over the span of a few days. In addition. 1.010 is in the reasonable range for a final gravity reading. I had many beers finish at 1.012 particularly when using extract.

I agree with what pvpeacock is saying above. I've had beers finish anywhere from 1.009 to 1.018 and still were completely done fermenting. The key is stable gravity readings. If you are in doubt you can always give the fermenter a little slosh and allow it to warm a degree or two over a few days. That might restart fermentation and give you another point or two drop but at 1.010 I wouldn't expect much change.

As I understand the biology involved the absence of fermentable sugars is the main reason fermentation comes to a stop. That is why the bottles carb up only after adding a little priming sugar and allowing them to set a room temp for a week or two.

Cheers!

 

[pharaohpierre]

The issue with high alcohol doesn't really play a role in the beer you are producing because at an OG of ~ 1.042, the amount of alcohol you produce isn't high enough to disturb most brewers yeast. This only really comes into effect when producing really big beers. I've used S-04 a lot of times for bigger beers around 8% with no issue.

I agree with the previous posts that a beer is finished fermenting when there is no more fermentable sugars for the yeast to metabolize. It could be 1.004 or 1.012, take a gravity reading when you think the fermentation is done and then take another gravity reading like 3-4 days later. If it hasn't moved then you can confidently assume fermentation is complete.

Now as far as the difference in your OG between the two batches, you could have accidentally assumed the wrong temperature or your efficiency changed between the two batches, either from incorrect temperature or water/grain ratio. That it can easily be fixed with understanding your equipment better, which comes with time.

 

[ElJayEm]

Thanks for all the replies. Beer hasn't moved from 1.010 but I'm now a bit more confident to ignore the hydrometer warning and bottle anyway.

So the yeast has stopped fermenting because it has run out of fermentable sugar. This presumably means the second batch contains more non-fermentable sugar since the final gravity is higher? I presume something slightly different in the mash or the slower sparge led to more in fermentable sugar being released?

 

[55x11]

Hi All,

A bit of background:

Having played around with kits in my youth I've returned to brewing and have just brewed my first all grain batches: Jim Line's London Pride Clone. I decided to work on the same recipe for the first few brews to hopefully make it easier for me to refine my technique and learn what's going on while keeping a lot of variables constant. I've scaled the recipe down to 1 gallon as follows:

700g Marris otter
50g crystal
50g demerara sugar

6g fuggles 12g Golding's at start of boil
3g Goldings at end of boil to steep for 15minutes
2g Golding's dry hopped for seven days, added after seven days of fermenting
Safale s04 yeast

Mash for 1:30 in cooler, strike at 70c
Boil 1:30

The first batch was bottled last weekend. I don't think I sparged for long enough and ended up with an OG of 1.032. This fermented down to 1.004 by the time I added the dry hops at day seven. The gravity didn't change for the next seven days before I primed and bottled giving me an FG of 1.004

The second batch was brewed a week later and I used a longer sparge and more sparge water. This gave me an OG of 1.042 which sounded more promising ( the recipe suggested 1.040). After a week in the fermenter I took a gravity reading when I added the dry hops. It was 1.010. I checked again two days later and it hasn't changed.

This has raised a few questions and I was wondering if anyone could help me out as I don't really understand exaclty what is going on.

1. Is 1.010 too high to bottle if it remains at this point for the rest of the week? The chart here: http://homebrewmanual.com/beer-gravity-chart/ would suggest that it's actually about right for an English bitter and I wouldn't have worried, but my hydrometer packaging says in bold writing not to bottle above 1.006 or 'bottles will burst!'. It even has a black line at 1.006 to make the point.

2. Why do yeasts stop fermenting? I thought it was because they ran out of fermentable sugar or because their environment was too alcoholic. If the environment is too alcoholic, why do they start fermenting again when priming sugar is introduced? If they have run out of sugar, how can two batches with the same recipe run out of sugar at different points?

These are probably stupid questions and I'm missing something obvious but I can't get my head around it.

Thanks

Your attenuation (apparent) from 1.042 to 1.010 is 76%, which is better than 75% quoted in S04 description:
http://www.fermentis.com/wp-content/uploads/2012/02/SFA_S04.pdf

Your beer is done. Bottle it. If in doubt, wait a few days and then bottle it.

Important thing is to measure on multiple days past 1.5-2 weeks or so, when all signs point to stopped fermentation and gravity is stable.

Having said that, I doubt it would drop much below 1.010 for you.