How to make a starter

A couple days ago, I had my first starter mishap after easily having 40+ successful starters using the same techniques. It made me go back and review some of my procedures to find where the mistakes could have been made. Thus, this seems like a perfect opportunity to create a tutorial on the ins and outs of starter making.

Question 1: Why do I need a yeast starter:

This is simple, to ensure you have enough yeast to ferment your wort. In most cases the amount of healthy yeast cells provided in the White Labs vials and Wyeast smack packs will not be enough. The generally accepted figure is that you will need 1 million cells/ml/degree Plato of wort. This may need to be adjusted under special circumstances but it holds true in most cases. White labs claims that their 50 ml vials are each “equivalent in cell count to a pint starter, or 75-150 billion cells” and Wyeast claims that their 125 ml packs “have a minimum of 100 billion cells.” Thus its safe to say that each vial holds approximately 100 Billions Cells.

Now lets do a quick calculation to determine the cells needed for a basic 1.050 sg ale (5 gallons):

5 gals = 18927.05 ml, 1.050 sg = 12.37 Plato
1,000,000 cell * 18,927.05 ml * 12.37 P = 234.12 Billions cells. Thus you need more yeast.

There are a couple of other points worth mentioning:

1. The vials could have more or less yeast then the average. The Wyeast is likely to have more because of the increased volume of the pack.
2. These vials/packs are only really viable for 4 months or so and should have an expiration date. Note that the older the yeast gets, the more dead cells you will have and therefore the more yeast you will need to compensate.

Step 1: How much yeast do you need?

This can be calculated using the equation above if you like. I prefer to use the Mr. Malty Yeast Pitching Rate Calculatorbecause this was built based on years of experience on the subject. This calculator will take a couple other factors into play when making the calculations. I ignored these before because I didn’t want to confuse you. These other facts are:

• The gravity of the wort: Higher gravity wort needs a higher pitching rate.
• Volume of wort: The more wort the more yeast you need
• Type of yeast used: Ale or Lager. Lagers are fermented at colder temperatures and therefore they require a higher pitching rate.
• Form of the yeast: liquid, Dry, or Slurry. Liquid yeast is very viable, dry yeast has more dead cells but lasts longer in storage, and slurries have TONs of yeast mixed with protein and hops.
• Oxygenation technique: shaking, with stone, stir plate. A simple starter with no oxygen versus one on a stir plate will affect how well the yeast grows. The better growth you get, the less yeast you need to start with.
• Viability of the yeast: how old is the yeast? This is really only a factor for liquid yeast.

With all this information it will tell you:

• How many cells you need
• Number of vials needed with and without a starter
• The size of the starter you need.
• It also adds a very handy slide bar that lets you change the vial parameters to see how that affects the starter volume.

Step #2: How much sugar do you need?

If you ask the yeast suppliers they will tell you to make a starter with OG of 1.040 sg or less. The primary reason for the low gravity is to keep the yeast in the growth phase for as long as possible. The point of the starter is to grow more yeast so you have enough for primary fermentation, thus you don’t want your starter to do much fermenting (producing Co2 and Ethanol). If you go to far over the 1.040 sg the yeast will spend less time in the growth phase and may skip it all together (this is called the “crabtree effect”).

Assuming you are using extract, find out how concentrated it is from the supplier. I generally use Briess Pilsen Light which requires 0.89 lbs of extract per gallon of water to reach 1.040 sg. This comes out to 92.99% dry basis, using my beertoolspro calculator. Scale this appropriately according to how many liters of starter you need and your all set.

Step #3 Make the starter 

Assumptions are that you have used the steps above to determine or starter volume, amount of vials you need, and amount of extract you will need.

Equipment you will need:

• Starter vessel: I use a Erlenmeyer flasks made out of borosilicate glass because it can be put directly on the stove and won’t crack when it changes temperature quickly.
• Ingredients: Yeast, extract, non-chlorinated water, yeast nutrients (optional(
• Stopper and airlock for the flask.
• Temperature probe that can reach liquid
• Wort oxygenation kit
• Sanitizer
• Stir plate and stir bar (both optional)

Steps:

1. Take yeast vials/packs out of the refrigerator and let warm to room temperature.
2. Sanitize all equipment (flask, stopper, airlock parts, stir bar, oxygenation stone, temp probe)
3. Fill flask with non chlorinated water to size specified. Add a little extra for boil off (the amount will depend on the surface area at the surface of the water)
4. Measure out your extract exactly and pour into the flask. I use a funnel and go slowly. When done shake vigorously until they are mixed.
5. Place the flask on heat at high setting. Wait till boiling. Turn down heat to prevent boil over but maintain boil for 10-20 minutes.
6. Add nutrients if desired.
7. Take of heat and place in ice bath to speed cooling.
8. Place a temperature probe in liquid and cool till between 70-75.
9. Use a refractometer or hydrometer to check the gravity. If it is too high, add room temperature non-chlorinated water to the starter to dilute it to 1.040 sg or below.
10. Oxygenate the starter for 15-30 seconds
11. Pitch yeast from vials or packs.
12. Put in stir bar if using a stirrer and place stopper and airlock on top
13. Maintain 70-75 degree F temperature for duration
14. If your planning on pitching starter as is, only two days ahead is needed (Thursday fir a Saturday brew). Otherwise you will want to do the starter 3-4 days ahead so you have enough time to decant the wort off the yeast.
15. To decant, wait until starter has finished. Place yeast in refrigerator for 1-2 days or until yeast has flocculated. Siphon liquid off yeast to desired level. Leave some liquid so you can shake the yeast cake off the bottom at pitching time.
16. Before pitching a decanted starter you can add some cooled 70 degree wort to it a few hours before. This will activate it and get it moving faster.

One thing I would like to call out is step #9. This is important because sometimes the extract you have may average on the high side. If this happens your starter will have too much sugar and you need to dilute it to prevent the crabtree effect.

Follow these steps and you should have just the right amount of healthy yeast every time you brew.