Pull Up A Stool with John and Chris Trogner

Founders, Tröegs Brewing Co.

July 10, 2013 By Julie Johnson

Is the Scratch series the starting point for all your new beers?

CT: It really is, though not in the conventional sense. For instance, when we did Perpetual IPA, we started brewing hoppy ales with different hop combinations. We did seven different recipes, none of them were Perpetual IPA: they were kind of dancing around different aromas and flavors. We were just trying techniques to see how to get the hop oils into the beer.

I understand you have a special piece of equipment to help in that process.

JT: The hop gun? Dry hopping’s a challenging technique. Traditionally you would climb on top of a tank, open a port and dump in hops. Which works well, but we found, the more research we did, hop oils stratify and create layers within a tank. Our goal was to make sure those hop oils dissolved in the entire column of beer the same way every time.

In order to do that, there’s a vessel we call a hop gun—it looks like a rocket. You purge it with carbon dioxide, put your hop pellets in, then you pump beer in from the fermenter. It’s kind of hard to explain, but the way we pump the beer, it develops a double helix flow. Where the double helix meet, it’s very turbulent, and that basically pulverizes the pelletized hops.

In the center of the hop gun is a perforated pipe that allows the dissolved hop particles and hop oils to exit the hop gun. It’s in consistent circulation, pulling beer from the bottom of the fermenter, dissolving the hops through that double helix flow, then pumping it back into the fermenter.

So instead of adding hops to the beer in the fermenter, you’re pumping it out of the fermenter, through this sort of tornado, then back into the fermenter.

JT: That only gets the hops into the tank, but it doesn’t ensure that the hop oil is consistently dissolved in the beer column. So, as it re-enters the tank, the beer hits one more step, called a Venturi. As the beer flows through the center of the pipe, it pulls in beer from the outside of the pipe, basically causing an explosive flow four times the rate of the flow entering the pipe, completely churning—that tornado effect—in the large tank as well. So, the hop gun has the double helix, and the fermenter has, let’s say, the tornado.

It must have been a riot the first time you hooked this thing up.

JT: (Laughs) We’ve been through a number of renditions by now. We’re constantly challenging ourselves regarding how we get flavor and texture and taste into each of the beers.

CT: To summarize, the Scratch beer series is kind of the platform for us to try new ingredients, new techniques that may be applied to a new beer, or it may just be to make us more knowledgeable brewers.