The Stir Plate - At a recent homebrewing meeting, my buddy shared a worksheet with needed yeast count and target gravity readings. I quickly realized that aside from a few of my smaller batches, I was usually under-pitching my yeast. I haven't lose a batch to infection and am usually pretty close to my target gravity, but I sure would appreciate reducing the risk if possible...and a bubbling airlock in a few hours puts us all at ease rather than waiting 12-15 hours like I have on some of my brews. I sometimes use dry yeast, activating it for about 4 hours before I pitch it, and usually use the "yogurt" vials at room temperature. Realizing I will need to pitch more yeast for my IPAs, Stouts, Porters, and Barley Wine this spring, I was faced with the thought of buying multiple smack packs of yeast...or multiplying the yeast. Smack Packs and additional Vials could increase the cost of my 5- or 6-gallon batches by $7. Over a year of brewing that would be an additional $50-$100. In the spirit of BudgetBrewery, I went with doing it myself, learning a little, and creating a better way to brew. I am not ready and don't brew enough for yeast harvesting, but I think a little ingenuity and planning ahead can be a great way to keep brew cost down.

Head over to my project page Here for details about assembly and cost of the items needed.

The idea behind the stir plate is pretty simple. Add a little Dry Malt Extract (DME) so it has something to munch on (and grows/multiplies) and keep it suspended by swirling the water so it doesn't settle. Pitching with the correct amount of yeast will get you a more "active" fermentation, meaning faster, more vigorous, and less chance of something else getting in there before the alcohol is produce. Also, some brewers get fermentation going first and then pitch this starter 12-18 hours later, but for me, I just add it all in at the beginning.

Establishing Ideal Yeast Cell Count

The perfect amount of yeast is determined by the beer batch’s volume in relation to the original gravity. An ale usually requires about 0.75 million viable yeast cells for every milliliter of wort per every degree plato. For example, a 5-gallon batch of 1.064 ale wort would require about 227 billion viable yeast cells:

There are 3785ml in a gallon so 0.75 million viable yeast cells x 18925 mL of wort x 16° Plato = about 227 billion yeast cells…Most fresh yeast packets come with about 1 billion yeast cells.

Getting Started

Gravity: Aim to have the gravity in the 1.030-1.040 range, which will promote healthy growth without introducing too much unneeded stress.

Temperature: Keep yeast starters 68-72°F. Room temperature is usually fine as long as it isn’t too cold.

Volume: Determining volume can be a very involved process. The volume of the starter in relation to the number of viable yeast cells added, the inoculation rate, will determine the growth potential for the yeast starter. For example, 200 billion yeast cells added to a 2 liter starter will have significantly less overall growth than adding 100 billion yeast cells to the same volume.

1. Determine the appropriate starter volume - use an online yeast calculator if this is a new recipe.

2. Add 1 gram of dry malt extract for every 10 milliliters of target starter volume.

3. Add DME and water to reach the target starter volume. Then add about 1/4 teaspoon of yeast nutrient.

4. Bring to a gentle boil right in your beaker or Erlenmeyer flask for about 15 minutes. Keep the boil vessel covered to maintain as much of the volume as possible. Cover with foil to prevent too much water from evaporating.

5. Chill to room temperature, set on the stir plate, and pitch yeast into starter wort.

6. Start stir plate and leave yeast away sunlight for 12-24 hours