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A forced fermentation is a process carried out by the QC/QA lab at the brewery. The objective of the force fermentation is to get an anticipated FG for the beer being produced. Of course brewing calculators can give you an anticipated FG but say one of your brewers mashed with a temperature too high for the recipe and you didn't get the conversion you expected. you may end up with a different wort profile and the end ferment gravity may be slightly different than anticipated. your beer finished at 2.0 P normally but now it's at 2.7P and it looks stalled out, you don't know yet that the mash temperature wasn't hit since it wasn't recorded(bad notes), how can you tell if it's actually done at 2.7, or if it's stalled out due to a yeast problem and can go lower?
1. PURPOSE
To calculate the theoretical FG of a fermentation by taking wort and force fermenting if with a large quantity of yeast in a short period of time and determining the gravity of the fement.
this determines the projected FG of each individual batch and can account for brewing errors giving a better FG anticipation than software
2. MATERIALS AND APPARATUS
1. Large Buchner funnel
2. filter paper
3. Side arm flask
4. Vacuum pump
5. 2L glass beaker
6. Magnetic stir plate and stir bar.
7. 500 ml Sample of thick yeast slurry (from your brinks!)
8. Hydrometer and cylinder.
9. A lab !
3. PROCEDURE
boil out the 2L flask with the stir bar in it(heat appropriate magnet)
I boil water in a microwave in a 1L cup then pour two of them in.
Push a piece of foil over the top of the beaker so it touches the boiling hot water and sanitizes it as well. before you put the foil over the top write the brand of the beer, the date, the batch number, the PFV # and any other data you think is important
now you have a super hot beaker full of water on your lab counter with the foil over the top and the stir bar is inside of it, set it aside to let it "sterilize"
now grab your side car flask and put the funnel in it. put it in the sink and pour boiling water through it to sanitize it all out
bring it over to your vacuum pump
and put one sheet of the appropriate filter paper for yeast in there
then take your thick yeast (8e8-1e9 cells per mL slurry)
and pour it in you want to be about 1.5-2 inches thick here in a 100mm wide Buchner
turn le-vacuum pump on and wait until it drys up and starts to crack away from the edges of the Buchner funnel and looks like the surface of the desert. (while this is happening 1-2 hours do the next step)
empty out the 2L beaker and put the foil back over the top don't drop the stir bar out but get all of the water out.
go to the brewery floor and sanitize the zwickel on the tank that has the beer just after hi-krauzen so it's not ultra foamy on you.
after the zwikel is sanitized fill the beaker to about 1400-1600mL full of product and put the foil back on the top. bring it back to the lab.
now take your super dry yeast, it should feel like a weird kind of cheese. you may need to slide a butter knife around the edge of the Buchner to get the yeast cake out. it will still have the filter paper attached to it. it's ok to handle it with your hands as long as you have good hygene. the cell count in the yeast brick you made is so high there's such a selective advantage you will not contaminate your forced fermentation by handling the yeast with your bare hands at this point
put the 2L beaker full of product on your stir plate and get it to a gentle vortex and add some anti-foam(trust me)
once it's at a nice gentile vortex add the yeast by breaking it into small pieces
there's two very important reasons we dried out the yeast with the Buchner funnel and the vacuum pump
one is so that the yeast is dry and doesn't contribute to the gravity reading we will take since the yeast from the force might be from a different product of beer(but has to be the same exact strain of yeast you're using in the forced fermentation product)
for example we may use the harvest stout Wyeast 1272 into brinks, then sample the brinks and keep some yeast in the lab for force fermentation down the road. Then we take that 1272 and use it for the porter forced fermentation since the porter also uses 1272 yeast.
the yeast slurry has it's own "gravity" but once it's dried out it will not have any liquid to contribute to throwing off your gravity reading of the force.
the other good reason for drying out the yeast is to concentrate it. the forced fermentation uses 1000s of times more yeast than is necessary for fermentation. since you're forcing with the same strain of yeast the real fermentation is for it will eat the same sugars in the same way but finish in 24 hours.
since we're stirring the force on the stir plate it will ferment much faster, also in that we are using 1000s of times more yeast than needed it also finishes astonishingly quick
let the forced fermentation stir for 24 hours
then take it off the stir plate and put it in the cooler, it will take hours to settle out
once it settles out you can take a gravity reading with your hydrometer and this is your forced fermenation
the number you read will need a temperature correction(force was in fridge to settle)
settling the yeast out of the force is important so it doesn't effect the gravity reading, in the same way you should filter or settle the yeast for your PFV gravity readings too.
now you know where your brewery fermentation theoretically should end up, it will tell you your FG based on the individual chemistry/composition of that specific batch of wort and how the strain of yeast will interact with it if given everything it needs to ferment correctly.
1. PURPOSE
To calculate the theoretical FG of a fermentation by taking wort and force fermenting if with a large quantity of yeast in a short period of time and determining the gravity of the fement.
this determines the projected FG of each individual batch and can account for brewing errors giving a better FG anticipation than software
2. MATERIALS AND APPARATUS
1. Large Buchner funnel
2. filter paper
3. Side arm flask
4. Vacuum pump
5. 2L glass beaker
6. Magnetic stir plate and stir bar.
7. 500 ml Sample of thick yeast slurry (from your brinks!)
8. Hydrometer and cylinder.
9. A lab !
3. PROCEDURE
boil out the 2L flask with the stir bar in it(heat appropriate magnet)
I boil water in a microwave in a 1L cup then pour two of them in.
Push a piece of foil over the top of the beaker so it touches the boiling hot water and sanitizes it as well. before you put the foil over the top write the brand of the beer, the date, the batch number, the PFV # and any other data you think is important
now you have a super hot beaker full of water on your lab counter with the foil over the top and the stir bar is inside of it, set it aside to let it "sterilize"
now grab your side car flask and put the funnel in it. put it in the sink and pour boiling water through it to sanitize it all out
bring it over to your vacuum pump
and put one sheet of the appropriate filter paper for yeast in there
then take your thick yeast (8e8-1e9 cells per mL slurry)
and pour it in you want to be about 1.5-2 inches thick here in a 100mm wide Buchner
turn le-vacuum pump on and wait until it drys up and starts to crack away from the edges of the Buchner funnel and looks like the surface of the desert. (while this is happening 1-2 hours do the next step)
empty out the 2L beaker and put the foil back over the top don't drop the stir bar out but get all of the water out.
go to the brewery floor and sanitize the zwickel on the tank that has the beer just after hi-krauzen so it's not ultra foamy on you.
after the zwikel is sanitized fill the beaker to about 1400-1600mL full of product and put the foil back on the top. bring it back to the lab.
now take your super dry yeast, it should feel like a weird kind of cheese. you may need to slide a butter knife around the edge of the Buchner to get the yeast cake out. it will still have the filter paper attached to it. it's ok to handle it with your hands as long as you have good hygene. the cell count in the yeast brick you made is so high there's such a selective advantage you will not contaminate your forced fermentation by handling the yeast with your bare hands at this point
put the 2L beaker full of product on your stir plate and get it to a gentle vortex and add some anti-foam(trust me)
once it's at a nice gentile vortex add the yeast by breaking it into small pieces
there's two very important reasons we dried out the yeast with the Buchner funnel and the vacuum pump
one is so that the yeast is dry and doesn't contribute to the gravity reading we will take since the yeast from the force might be from a different product of beer(but has to be the same exact strain of yeast you're using in the forced fermentation product)
for example we may use the harvest stout Wyeast 1272 into brinks, then sample the brinks and keep some yeast in the lab for force fermentation down the road. Then we take that 1272 and use it for the porter forced fermentation since the porter also uses 1272 yeast.
the yeast slurry has it's own "gravity" but once it's dried out it will not have any liquid to contribute to throwing off your gravity reading of the force.
the other good reason for drying out the yeast is to concentrate it. the forced fermentation uses 1000s of times more yeast than is necessary for fermentation. since you're forcing with the same strain of yeast the real fermentation is for it will eat the same sugars in the same way but finish in 24 hours.
since we're stirring the force on the stir plate it will ferment much faster, also in that we are using 1000s of times more yeast than needed it also finishes astonishingly quick
let the forced fermentation stir for 24 hours
then take it off the stir plate and put it in the cooler, it will take hours to settle out
once it settles out you can take a gravity reading with your hydrometer and this is your forced fermenation
the number you read will need a temperature correction(force was in fridge to settle)
settling the yeast out of the force is important so it doesn't effect the gravity reading, in the same way you should filter or settle the yeast for your PFV gravity readings too.
now you know where your brewery fermentation theoretically should end up, it will tell you your FG based on the individual chemistry/composition of that specific batch of wort and how the strain of yeast will interact with it if given everything it needs to ferment correctly.
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