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Contents
Why This is Important and/or Interesting
It’s always a good idea to pitch an adequate number of yeast cells to provide a healthy fermentation. Doing so can be the difference between great or not-so-great beer. This Homebrew Note will show you how to calculate the number of cells you need.
Items Needed
- Internet Connection (you’re reading this, so CHECK!)
Process Gallery
Have a quick look at the gallery photos by clicking on the first image and reading the captions as you click your way through the images. Then read the section below for context.
Process: Calculating How Much Yeast to Pitch and the Size of Your Starter
Use a yeast starter calculator to determine how large of a starter your beer needs. There are many available online but I use this one from Brewer’s Friend: https://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/
For the purposes of explaining this calculator, it’s helpful to use a specific example. Feel free to substitute the information from your upcoming brew session instead.
Example information:
- Target brew/batch volume = 5.5 gallons
- Beer type = IPA (ale)
- Target gravity = 1.055
- Yeast type = liquid
- Yeast pack = 1 pack of liquid yeast manufactured on 2019/01/01
- Stir plate available = yes
Enter the calculator data:
- Units – US or metric depending on your preference
- Sugar Scale – Your recipe’s estimated original gravity in gravity terms, e.g. 1.055 (what I use), or Plato, depending on your preference
- Wort Gravity – Target gravity for the homebrew you plan to ferment with this starter (1.055 in the example)
- Wort Volume – Target fermenter volume for the homebrew you plan to ferment with this starter (i.e. How much is going in your bucket/carboy?) (5.5 gallons in the example)
- Target Pitch Rate – This is subjective depending on your preference. I use the Pro Brewer option that’s one higher than the minimum for the style I’m brewing. My philosophy is to target having more than enough healthy yeast since these step-ups will not result in over-pitching. The minimum for your style should be sufficient so doing a step higher is purely optional.
- Normal ale with a gravity below 1.060 – I use the Pro Brewer 1.0 instead of Pro Brewer 0.75 (used in the example)
- High gravity ale above 1.060 – I use the Pro Brewer 1.25 instead of 1.0.
- Lager – I use Pro Brewer 1.75 instead of 1.50.
- Yeast Type – Liquid (see box out note below on dry yeast)
- Liquid Packs – Typically one but if you have a large brew volume or a high gravity beer, you may choose to start with more than one pack to reduce the size of your starter. (used 1 in the example)
- Mfg Date – The date your pack of yeast was manufactured (found on the yeast pack itself). Yeast loses viability each day so knowing when it was made is important. (2019/01/01 manufacture date in the example)
NOTE: Yeast starters are typically only done for liquid yeast because of the cost differential and the amount of effort involved. Liquid yeast packs are $7+ whereas most dry yeast packs are $4+. Since making a starter is fairly involved and has a cost of its own for DME, most people opt to just buy multiple packs of dry yeast if the calculator indicates a need for a starter. However, even if you’re using dry yeast, I’d still suggest that you use the calculator to help you determine how many dry yeast packs to buy.
IMPORTANT: When you’re buying yeast, the manufacture date is very important since it determines how viable that yeast is. It’s important to flip through those packs and find the most recent one. If the yeast was manufactured more than six months ago, I wouldn’t recommend using it. Personally, I won’t buy one more than four months old unless it’s the only option available and I’m on a time crunch.
NOTE: If you want to geek out with more explanation on any of the Brewer’s Friend yeast calculator’s functions or values, scroll to the bottom of the calculator where Brewer’s Friend explains everything in detail.
Click the Update button and note the Viability details. Don’t panic if it says your yeast viability is estimated to be low. The purpose of a yeast starter is to propagate more yeast and get you to a healthy pitch rate for a strong fermentation. A low viability just means your yeast starter volume will be larger.
Now you begin tinkering with the yeast starter variables to figure out what works best for you. Click the Grab from Above button and enter the starter data:
- Starter Size – This is the volume of starter you’ll be targeting. For now, think of it as the amount of water you’ll use. (1.5 L was the perfect volume in the example)
- Gravity – Keep the gravity between 1.030 to 1.040 in order to keep the yeast in its growth phase, rather than its fermentation phase. The fermentation phase will create alcohol which can be toxic to yeast in high concentrations. (1.040 used in the example)
- Growth Model & Aeration – If you’ll be using a stirplate, select Braukaiser – Stirplate. If you’ll be putting the starter in a container and shaking it on occasion, choose C. White – Shaking. If you won’t be able to use a stirplate or to shake the starter, choose C. White – No Agitation. (Stir plate used in the example)
Enter a 1L starter size and 1.040 gravity to start and click the Update button. Now check the Resulting Pitch Rate box just below the Update button. If it shows, “Starter meets desired pitching rate!” you’re in good shape. If it says, “Starter does not create enough yeast cells.” you’ll want to progressively increase the Starter Size (e.g. , 1.1L, 1.25L 1.5L, 2L) and click Update until you meet the desired pitching rate. Once you have reached the desired pitching rate, make note of the Starter Size volume and the DME Required results. You’ll need those when it comes time to make your yeast starter.
You’ve successfully calculated how much yeast you’ll need for your homebrew! Now save and/or print the summarized Homebrew Notebook Page for use in the future.
Now that you’ve read this Homebrew Note, let me know if you have a question, recommended improvement, or other thoughts in the comments below. As I mention in About Homebrew Notes, these are living documents and your feedback is appreciated!