By Anthony St. Clair
For the Oregon Beer Growler
Wrangling yeast can be as easy as moving it from one fermenter to another. Unless you have four yeast strains in regular use and a tight production schedule that can’t always wait for the yeast to be ready. That’s why, earlier this year, Eugene-based Ninkasi Brewing Company brought online a dedicated system of yeast propagation and storage tanks.
“Yeast is the only raw ingredient we supply ourselves,” says Dr. Daniel Sharp, director of brewing process development. “In addition to beer, we also make yeast, so having dedicated vessels for making and storing yeast is no-brainer, especially due to the amount of beer we make and how many yeast strains we use.”
Originally championed by Ninkasi’s in-house lab and quality control teams, the propagation system (“prop” for short) arrived earlier this year. “Before having this system, we were all doing this with our current brewing and tank setup, trying to fit it in and make it work,” says Sharp, “but that’s challenging when you have all your fermentation vessels full. But you need vessels to make yeast to make more beer. It was an easy ROI, and it makes yeast production easier for the whole team.”
The custom-made system was fabricated by W.M. Sprinkman, a dairy, food and beverage equipment manufacturer in Wisconsin. The system is comprised of three 10-barrel brinks and one 5-barrel brink for storage as well as 20- and 30-barrel props. Controls include gravity, gas composition (vessel atmosphere), agitators to aid cooling and homogeneity, and temperature. For oxygen, “we used to use a standard dosing rate, like most brewers, added at the beginning of fermentation,” says Sharp. “Now we can add oxygen based solely on how much the yeast needs to grow, instead of how much it needs to ferment. We’re still working with it to figure out the optimal amounts, but playing with the oxygen levels for the yeast is helping us grow healthy yeast faster.”
A positive displacement pump, great for moving thick liquids while being gentle on the yeasts, is used for transfers. After yeast is grown in the lab, it’s added to the prop and then pitched into wort during knockout. One 30-barrel batch of yeast can pitch a full 550-barrel fermenter. Instead of pitching by volume, the tanks are connected to load cells, so Ninkasi’s brewers know how much yeast is being pitched down to the pound. “We also don’t like to waste things, especially yeast,” says Sharp. “Nailing in exactly the amount we need when we need it, that’s the goal.”
Installed and tested during March and April, Ninkasi uses the system for the full yeast propagation process. The benefits have been immediate. Yeast propagation used to take 14–21 days. Now it can be done in 10–12 days.
“The shorter time helps us be flexible and work with the yeast while it’s in a happy state,” explains Sharp, “while also working with the other needs of the production schedule. We look out weeks in advance, and the shorter time is a big win.”
Parallel environments ensure optimal conditions for both beer and yeast. “Fermentations are great for making alcohol but aren’t good conditions for yeast growth,” says Sharp. “The conditions for growing yeast are bad for beer, such as needing oxygen. With the props we can grow a healthy supply of our own yeast without compromising beer flavor. Also, by controlling the conditions of our yeast growth and health, we can better control the subsequent fermentation profiles.”
Depending on the schedule, now yeast can be taken straight from one fermenter to another, or it can be stored in a brink and used for up to 10 fermentations. With four strains in regular use (Helles Lager, English Ale, Chico Ale and German Ale), plus a house yeast library for special projects, it’s also easier to maintain the “yeast pipeline” so that yeast is at an optimal state for pitching. For example, the English Ale strain — used in flagship beers such as Total Domination IPA — is a “juggernaut” that has adapted well to Ninkasi’s brewery and higher-IBU and ABV beers, while providing softer blending aromas and flavors.
“We don’t do delicate yeasts that need coddling,” says Sharp. “We need tough yeasts.”
On the flipside, for a beer such as Hop Cooler IPA, the Chico Ale accentuates individual characteristics, and the German Ale yeast used in Sleigh’r Dark Double Alt Ale is less flocculent, so some residual yeast remains for a thicker mouthfeel.
“We are a yeast farming facility that makes good beer,” says Sharp. “Our job is to make good yeast, or we can’t make good beer.”
Stories from the print edition of the Oregon Beer Growler.