In my last post I discussed why we need to pitch the right amount of yeast. I also discussed how to determine how much yeast you should be pitching. To refresh, you need roughly 4 Billion cells per gravity point in Standard Gravity (SG). So, a 1.056 beer needs roughly 224 Billion cells. Now, lets discuss how to do a yeast starter to get that 100 Billion cell liquid yeast pack up to a accurately pitchable amount. Since we are just looking for yeast growth--not fermentation--we want to prepare our starters 18-24 hours before pitching. Also, remember from my last post, you will have 1.3x growth in a 1L, 2.3x in a 2L, and 3x in a 4L. So, be sure to keep those volumes in mind during prep.
The recommended equipment needed is our Yeast Starter Kit that has a combination of the following:
- Heat source, gas or glass-top stoves work best
- 5000ml Erlenmeyer flask (remember, bigger is better--go big from the start)
- Pilsen DME, can also use an extra light
- Spring water or filtered tap water (always filtered)
- Ice for an ice bath
- Yeast nutrient
- Stir plate (or plan to shake the flask regularly)
- Stir bar
- Aluminum foil
- Star San
The advantage to the Erlenmeyer flask is that it can be boiled directly on a gas or glass top stove. I recommend the 5000ml because it gives you the ability to boil a larger starter size. We are shooting for a gravity of about 1.030-1.033 SG. We accomplish this by using 100g (approximately 3oz) of DME per liter of starter. If you are making a 2L starter, you will need 200g of DME and enough water to make 2000ml. (Note: It's not 200g + 2000ml of water). If you are using a Wyeast pack, go ahead and activate the smack pack before you mix or heat. If you are using White Labs, leave the pack out to warm up. Mix your DME and water well, I use a large 5000ml graduated flask for this because it allows room for mixing and volume. After mixing, bring the mix to a boil. Once you reach boiling, add approximately 1/4 tsp of yeast nutrient. Boil for 10 min. While you are boiling, pull off approx 1 foot of foil and spray with sanitizer. Once your 10 min boil is complete, cover neck of flask with sanitized foil, and place the flask in an ice bath. (Note: Make sure the ice water level is LOWER than your wort level in the flask. You can crack your flask if your ice bath is larger. And though Erlenmeyers are meant for temp variation, better safe than sorry.)
Once your starter wort is cooled, you are ready to pitch your yeast. Sanitize your stir bar, a pair of scissors, and the yeast packets. Drop the stir bar into the flask, pour in your yeast, and replace the sanitized foil. Set your flask on the stir plate and turn it on. Make sure that your stir bar is caught by the magnetic pull of the plate. We are looking for a small dimple in the surface that proves the wort is mixing. Don't try to make a huge vortex. If you try to spin the bar too fast it is more likely to get thrown off the magnets. We want it right in the middle because we are trying to keep the yeast in suspension and encourage growth. Prior to pitching, you can decant the excess liquid and pitch the yeast slurry. This standard practicel if you are making a larger starter. Otherwise, you can pitch the entire amount into your fermenter, just remember to catch the stir bar!
And there you have it. With the right volume and time, you will have the right amount of yeast for that better batch of beer. Just remember that you can allow the starter to settle for a short time before you decant to collect the most yeast in the least amount of liquid (aka unhopped beer). Too much extra starter wort could possibly throw off your estimated gravity if your batch was a little short on volume.
Mikey has been brewing since 1997 and moved onto all grain in 2012. He has worked at Texas Brewing for 4 years now. You can usually find him there on some Fridays and most Saturdays. He's also available by email at firstname.lastname@example.org.