Yeast Starters and Building a Quick/Dirty GhettoBlasting Stir Plate

Yeast StarterOne thing you might hear about as you get further along into homebrewing is the need for a “yeast starter” or “pitching rates.”  Below 1.060 gravity you can still get away with a single smackpack or vial of yeast and end up with a fermentation that finishes and has enough oomph to clean itself up afterwards.  But when you start looking into big Imperial style beers, barley/wheat wines, Double IPAs, etc a single serving of liquid yeast is simply not enough yeast to finish off such a big plate of sugar.  So now we need to make a starter!

erlenmeyer_small_For a typical big beer between 1.060-80 you will need at least a 1-Liter Erlenmeyer flask and you will need some DME (Dry Malt Extract) and you will need to brew up the DME for 1.040 of yeast starter goodness.  You need about 10g of DME per 100mL of starter so 1L will come in at 3.5 oz of DME boiled in 1L of water for about 15-20 minutes.  What I like to do is get the water boiling in the Erlenmeyer flask to sanitize it and then carefully pour the boiling water into a saucepan and boil the wort with the DME.  Once you have boiled the wort pour it back into the Erlenmeyer flask and chill it down like you would if you were brewing a small beer.  An ice bath in the sink will suffice.  This is why I put the wort back into the flask because I have found that the flask fits easier in the sink than a saucepan with a handle.

Once the wort is cool go ahead and pitch your yeast into the wort and allow 24-36 hours for the yeast to have reached their maximum population for the volume of wort given.  Aerate the wort as you would normally as well and place enough aluminium foil over the top to cover the flask but do not make the container airtight.  The yeast require that oxygen to grow optimally for the next 24 hours. Also keep in mind that increasing the gravity WILL NOT increase yeast count. It will only increase stress.  Less gravity will have a negative impact on yeast growth however so 1.040 is found to be a “sweet spot” so to speak.  Creating this starter will typically increase the number of cells from a pack/vial of 100 billion to 130-150 billion cells for a 1L starter.  Again, as I said if you need more cells you can go with a 2L starter and get ~180-200 billion cells.  Brewing a 1.110 OG barleywine and need about 350 billion yeast cells you say?  Well, that is where the stir plate comes in!
A stir plate will actually DOUBLE your yeast cell count from a non-agitated yeast starter.  So your 1L starter that produces 135 billion cells will jump to about 260 billion cells if properly agitated for 24-36 hours.  Agitation is a process that keeps the yeast cells from flocculating out of suspension, which also inhibits their continued growth.

You can spend upwards of $100 for a cheap stir plate or even more for a professional agitation unit OR…. You can build your own for anywhere between $15-30.

I just recently built one using this video as inspiration:

The one place where my build differs from Fo’s is I used a Thermaltake Mobile Fan II External USB cooling fan for the magnet mount.  This somewhat limits where I can plug in my stir plate as I don’t have a laptop but I didn’t feel like splicing the wire.  Splicing wire is not hard at all but I’m lazy and just felt like going the USB route and it works great.  Make sure you have a variable control for your fan RPM however.  When you first plug in/turn on your stir plate with your suspension in place the bar may not move right away and you will need to slowly increase the rate of spin to get it turning, taking care not to “throw” the stir bar.  Once the bar is turning you can then turn down the RPM if you so choose or leave it where it is.  As far as I know the speed at which the bar is spinning has little to no effect on the actual process.  So long as you are agitating the yeast cells and keeping them from flocculating and settling out, your stir plate is doing its job.

Here are some before/after screenshots from Beersmith showing its calculated difference between using a stir plate and NOT using a stir plate:
noSP_small_zpseac6bdf3No Stir Plate

yesSPsmall_zps5ed5d3db With Stir Plate

That is about it.  Here is a quick video of my own build in action:
http://www.youtube.com/watch?v=1pac4hHRYqs&feature=youtu.beI
I purchased the fan and stir bar on Amazon, the project box and magnets were purchased from my local Radioshack, and the mountings for the fan/variable control were purchased at Lowe’s. If you have any questions or comments feel free to email me or comment on this article.  Thanks for reading!
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One thought on “Yeast Starters and Building a Quick/Dirty GhettoBlasting Stir Plate

  1. Pingback: Brewing Big Beers With Small Equipment |

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