Kick Starting Your Brew
All About Beer Magazine - Volume 32, Issue 2May 1, 2011
After 24 years of homebrewing, I am still mesmerized by the hypnotic churning and billowing suds of fermenting wort as it is metamorphosed into beer by the humble fungus, yeast. More than a mere catalyst, yeast can exert the most influence of any ingredient. There is a vast assortment of single strain and specialty blends of liquid yeast, and even cultures that mimic the micro-floral soup of spontaneously fermented brews, something unimaginable just 20 years ago. Even dried yeast manufacturers have recently broadened their portfolio. There is something for every brew, but selecting a strain is only the beginning. Optimizing yeast performance is as critical. Mangling an otherwise promising batch of beer with subpar yeast handling is a lot of effort down the drain, literally. And no amount of doctoring will salvage a poorly fermented beer. Learning a few of the yeast basics will have an energizing effect on both you and your brew. Yeast is the engine that drives the process, and the following are some simple instructions to prepare a potent starter for a five-gallon batch of brew.
Liquid YeastThere has been no more profound addition to the homebrewer’s arsenal in the past two decades than liquid yeast. Wyeast Laboratories and White Labs offer about 100 products between them, complete with detailed specifications and other vital information. Check out their websites and learn to dissect the specs and applications. Healthy yeast starters, followed by proper aeration, help ensure full fermentation and desirable characteristics, while suppressing off-flavors. Wyeast Labs offers two formats, the Activator pouch (pitchable), and the Propagator pouch (starter needed). White Labs offers the pitchable tube only. “Pitchable” means that the liquid culture can be added directly to five gallons of wort, maximum gravity 1060. The Wyeast Labs Propagator needs a starter as described below to get the proper, pitchable cell count. I use a 2-liter Erlenmeyer flask, stir bar and stir plate, but a saucepan and growler will suffice.
SanitationKeep a spray bottle of isopropyl alcohol handy to keep surfaces free of contamination. Use it on the outside of the pouch, the exposed surfaces of the starter container, foil covering, your hands and scissors.
TimingSmack your pouch (according to package directions) one or two days before you want to pitch into your starter solution, and four to five days prior to your brew session. There should be some evidence of activity (swelling) within 24 hours. If there is not, hold off on making the starter. If there is none after 48 hours, you may need a different pouch. Never mail order liquid yeast during hot weather unless the vendor can assure you that it will be shipped with a cold pack: cargo trucks get mighty hot.
Making the StarterAlways use DME (dried malt extract―easiest) or liquid malt extract (messy), as this will acclimate yeast cells to wort conditions. Do not use simple sugars, like table or brown, as this will encourage the growth of underperforming yeast cells. Optimal gravity for a starter solution is about 1.040. This offers enough substrate (maltose) for adequate cell growth, and minimizes osmotic stress on the yeast. The minimal volume to prepare is one quart. Dissolve 1/2 cup (3 ounces) of DME in 1 quart of water, add a pinch of yeast nutrient, heat to a gentle boil for 15 minutes, and cool to room temperature. A 2-liter Erlenmeyer flask placed directly on the stove is best (with a loose cover of foil), but absent of that, boil your starter in a small saucepan and transfer to a sanitized growler and cap. Either can be used on a stir plate with a stir bar. A 1.5 or 2 quart starter is even better, but will require decanting of the liquid prior to pitching. Lager beers, in particular, will benefit greatly from a larger starter.
AerationAerate the starter by shaking the growler vigorously for a minute or so. If using a stir plate, turn up the stirrer speed until you get a nicely dimpled surface that pulls air down into the liquid.
Inoculating the StarterThe smack pack should be fully expanded before you proceed. Spray the pouch and a pair of scissors with isopropanol, shake off the excess, cut the pouch, and empty the contents into your starter wort. The pouch has a tearing notch, but I prefer to keep my fingers off of the surfaces. Crimp a piece of sanitized aluminum foil over the opening of your growler or flask instead of an airlock for better air exchange. You should see activity within a few hours. If not, give it a swirl or increase the speed of your stirrer to see if it kicks up any dissolved CO2. During the growth stage, swirl the growler occasionally to help CO2 escape, keep the yeast in suspension, and dissolve more oxygen into the starter wort. A stir plate will do this automatically. Stir plates can generate heat; if yours does, put some cardboard or Styrofoam between the plate and flask or growler.
Inoculating Your WortYour starter should reach maximum activity, called “high krausen” within 24 to 48 hours of inoculation. Ideally, you’ll want to brew your beer and pitch at, or within a few hours of high krausen, but a few hours beyond that is OK. You can pitch a cleaner yeast slurry by sedimenting the yeast after high krausen and decanting the liquid. Put your starter in the refrigerator for a few hours to sediment the yeast, and simply pour off the liquid and discard. Allow the slurry to come to room temperature once again before pitching. Your beer wort and starter should be at room temperature (65 to 75 degrees) before pitching for both lagers and ales. Once the yeast is pitched and there is some sign of activity, you can bring the fermenter to the desired fermentation temperature. Don’t forget to fully aerate the wort. Under-aeration will prolong the period of time that wort is susceptible to contamination or create sluggish fermentation resulting in glaring flaws in the finished beer, negating all of the work you have done to this point. Aeration by agitation is more than sufficient, but another option to rig up a filtered and pumped air or pure oxygen system. Homebrew shops sell the supplies to use the forced air/oxygen method, complete with diffusing stone.
Starters for Strong BeerWort above OG 1060 will require an even higher cell count than those of lesser gravity. Here are the options: make a 1 quart starter (OG 1040) and inoculate with Wyeast Propagator, Wyeast Activator, or White Labs pitchable vial and ferment to completion. Chill and decant the liquid, and add a quart of 1070 starter wort to get the necessary cell count. Pitch at high krausen, or within 24 hours thereafter, in any beer wort up to OG 1100.
K. Florian Klemp
K. Florian Klemp is an award-winning homebrewer and general hobbyist who thinks there is no more sublime marriage than that of art and science.