Monday, 14 June 2010

Green Bullet Gold Yeast Count

As promised, I did a yeast count on the Green Bullet Gold.  For this I used a plastic container to hold my sample, a pipette, a hemacytometer and a microscope.  I just take a small sample of the beer, a few ml, from the sample tap on the FV.  I then draw a load of it into the pipette and squeeze it back into the sample a few times.  This helps to break up any clumps of yeast and also degasses it.

The hemacytometer is a thick glass slide that has two chambers each holding 1/10000 of a ml.  These chambers have an accurately grid etched into them which effectively allows you to count the cells in a known volume of beer. I take the coverslip and plonk it onto the hemacytometer so that it covers both of the chambers.  Then I draw a small quantity of the sample into the pipette before squeezing until a droplet is hanging off the end of the tube.  This droplet is then offered up to the edge of the cover slip where it is drawn ito the chamber.  I repeat this on the other chamber.  Take a look here to read more about how to do it.

Actively fermenting beer has about 60,000,000 cells per ml but as the fermentation subsides this reduces and the yeast drops to the bottom of the FV.  At racking you're looking for there to be about 1,000,000 cells per ml.  At this point there's enough yeast to ferment any priming sugar to carry out the secondary fermentation without causing excessive bottoms.  This means the cask will settle quicker and bottles will just have a film of yeast in the bottom rather than a thick sludge.

So, in my Green Bullet Gold I have 890,000 cells per ml which is typical of WLP002 or Fullers yeast.  It drops like a stone.  Based on this I'll set the FV temperature controller to start cooling in the morning and will rack to cask on Wednesday evening.

Back to brewing after a small break

Well, I haven't posted on here for some time as I have another addition to the brewing staff (see the photo to the right).  So, as I'm sure you can imagine, finding time/permission to brew can be a little tough right now.

Anyway, while I haven't yet brewed a commemorative beer I have been back in the brewery.  So, what's happened since my last post?  Well, I've fixed the heat exchanger (cleaned up all the old glue and remade it with "Marine JB Weld") and I've brewed another Green Bullet Gold, as it got such praise from the North Hants Brewers back in February.  This time, though,  I didn't have any flaked maize so I used flaked rice instead.  This will probably make very little difference; maybe a slightly less sweet beer but we'll see.

The brewday planning went a little wrong as I had planned to get the yeast starter ready for Sunday a couple of weeks back week but instead made the decision to brew a day early with only 2 litres of starter rather than stepping it up to 4 litres as I usually do.  As a result the beer took about 36 hours to get going properley.  It also slowed down quite a lot by the end of the week and has now been static at 1.011 for the last 2 or 3 days.  So, it's done (and it tastes great).

As usual, the WLP002 has dropped like a stone.  I'll do a yeast count later this evening if I get the chance.  So long as it's down to below 5 million cells per ml of beer I'll chill the lot down to 5°C for a couple of days before casking it.  I'm on call this week and I can't drink so there's no real rush to get this into a drinkable state.  Next week things will be different and I'll be taking every shortcut I can no doubt!

edit: I've just noticed that this blog is being followed by the Triple fff brewery who supplied the hops (they were surplus to requirements) free of charge.  Thanks, they're still making great beer despite their age!