Yeast and Stirplate

[b20653]

All,

I am fairly new to brewing but I have had two failed fermentations where I had to pitch a back up yeast. I think one time the yeast got too hot(summer) and the second time the yeast may have froze(winter) in shipping.

I have decided to do yeast starters to try to prevent myself from pitching bad yeast. I have also decided to do a stir plate, but I have one question. From what I can tell online without a stir plate you can expect to see krausen in about 15-24 hours to know you have a good starter. With a stir plate I would think you just see darkish liquid that is constantly moving so how do you know you have a good starter or not? I am assuming the krausen would not form with all the motion but I don't know. Any ideas or techniques would be greatly appreciated.

 

[pabloj13]

All,

I am fairly new to brewing but I have had two failed fermentations where I had to pitch a back up yeast. I think one time the yeast got too hot(summer) and the second time the yeast may have froze(winter) in shipping.

I have decided to do yeast starters to try to prevent myself from pitching bad yeast. I have also decided to do a stir plate, but I have one question. From what I can tell online without a stir plate you can expect to see krausen in about 15-24 hours to know you have a good starter. With a stir plate I would think you just see darkish liquid that is constantly moving so how do you know you have a good starter or not? I am assuming the krausen would not form with all the motion but I don't know. Any ideas or techniques would be greatly appreciated.

It will start to look like chocolate milk. Sometimes a small krausen will form but often it is knocked down by the vortex. Best way to tell is let it grow and then cold crash it and see if your yeast layer is bigger. Also, if you stop the stir plate and agitate it a little often you will see it foam up, indicative of CO2 in solution and active fermentation.

 

[DSmith]

Beside the chocolate milk/latte look, you can also tell by measuring temperature of the flask with a small piece of insulation taped to it and a digital thermometer. If the wort is about room temperature when pitching yeast, the temperature will go up and return to room temperature when the starter is finished. I wouldn't use that to determine when to put the starter in the fridge is you are going to decant. But it's more proof that you're on the right track when activity is very hard to see on the stirplate.

 

[pabloj13]

Beside the chocolate milk/latte look, you can also tell by measuring temperature of the flask with a small piece of insulation taped to it and a digital thermometer. If the wort is about room temperature when pitching yeast, the temperature will go up and return to room temperature when the starter is finished. I wouldn't use that to determine when to put the starter in the fridge is you are going to decant. But it's more proof that you're on the right track when activity is very hard to see on the stirplate.

As long as your stir plate doesn't heat the wort on its own like mine does. I guess it would never go back down if that were the case though.

 

[DSmith]

I use a silicon cooking pad (pic below) when doing starters so I can jam the tip of a digital thermometer under the flask for temperature readings, and it's a guarantee no heat is transfering from the stirplate to the starter. It proved to be easier than the insulation I mentioned earlier but gets the same result for temperature measurment.

I've seen a temperature rise and fall back to the room temperature on a few starters now.

 

[Mugsfull]

With Dry Yeast, there is no need for a starter. Its cheaper so I use it quite a bit. SafeAle04 or Nottingham are great yeasts and I've never had them fail.
I store them in the freezer.
I always proof the yeast before using. That means I add a little warm wort and water to a small sanitized dish. Add the dry yeast and wait 10 - 15 minutes and you should have bubbles all over the surface. That test ensures your yeast is healthy.
With Liquid yeast from white labs or Wyeast I always make a starter. I boil 1.5 qts water add 1/2 cup Dry Malt Extract and cool. You can adjust the gravity of your starter to be similar to the beer that you are brewing. Once the starter cools, I pour it in my flask, pitch the yeast and put in on the stirplate. I like to do this 2 days before brewing, but I've done it 24 hours prior and pitched at 'high krausen' with good results as well.
I've never thought about the heat transfer in the stir plate, its an interesting detail and I wonder what effects positive or negative it may have.