Day 178

In January, we tried to grow petri dish cultures using bacteria and wild yeast you can probably find around the house (or college). Today in Microbiology Lab, we tried not to grow a culture–or at least we have our fingers crossed that we will not succeed.

The reason we don’t want to see anything in our petri dishes is that we were testing fermenting wort from the Teaching Brewery for beer-spoiling bacteria.

Yep, we marched down to the Teaching Brewery in our lab coats and took a sample of wort from Larry (one of the fermenting tanks). Back in the lab, we plated a droplet of the wort on MacConkey agar, a growth medium that inhibits anything except the types of anaerobic bacteria that can spoil beer. Now we will wait for five days and hope that our petri dishes remain spotless.

In Packaging, apparently the class as a whole did not grasp the principle of how to carbonate beer, as evidenced by the answers we gave on our last quiz. (Sample answer: “Add carbon dioxide.”) So Doug Pengelly went over the procedure again step by step.

Then it was back to draught systems, specifically how to balance a long draught line so that the beer comes out of the tap at a reasonable rate of about 65 mL per second–enough to fill a pint glass in about 6-8 seconds.

To arrive at that happy place, we needed to understand the opposing forces in a draught line. On one side, the gas pressure is trying to force the beer through the line. On the other side, the line itself provides a certain amount of resistance, as does the tap and shank. If the keg is down in the basement, gravity is also holding the beer back. So given a beer keg cooled to 6°C in a basement fridge 16 feet below the tap, with a line run of 40 feet of ¼” barrier pipe (a special type of draught pipe), we calculated that

  • we needed to have a pressure of 33 psi of beer gas to maintain the equilibrium of the CO2 in the beer
  • gravity will add a resistance of 16 feet x 0.5 psi per foot = -8 psi
  • the barrier pipe will have a resistance of 40 feet x 0.3 psi = -12 psi
  • the tap and shank will provide a further -3 psi resistance

Since our total gas pressure is 33 psi, but our line resistance is only 8 + 12 + 3 = -23 psi, the pressure at the tap is going to be 10 psi–about twice the necessary force–therefore the bartender is going to get very wet when that beer shoots out of the tap, hits the bottom of the glass and rebounds up into his face.

In order to decrease the flow rate, we needed to increase the line resistance using special “restrictor” tubing: 5/16″ vinyl tubing that adds -3 psi of resistance per foot. In this case, since we needed to increase line resistance by about 5 psi, we would add about 1.5 feet of restrictor tubing, bringing total resistance to -33 psi. With only 5 psi of gas pressure left to push the beer, the beer will come out of the tap at a respectable pace.

Immediately following Packaging, some of us travelled up the QEW to Black Oak Brewing in Toronto, where a “hop nosing” was about to start. The owners of Puterbaugh Farms, an independent 600-acre hop operation in the Yakima Valley of Washington State, had arrived with about a dozen varieties of their hops. Several Ontario organic hop farmers, including Mike Driscoll, were also on hand with samples of their wares, and Doug Pengelly (who had been teaching us about balancing draught lines an hour before) arrived with fresh-baked hop bread. A lot of small craft brewers were present–I chatted with Paul Dickey of Cheshire Valley Brewing, Charles McLean of McLean’s Ales and Ralph Morana of House Ales, among others, as well as our sensory evaluation instructor Roger Mittag and program coordinator Kevin Somerville. After a bit of a social time and a talk from the owners of Puterbaugh Farms, we moved on to the actual nosing part of the program. The idea was to take some hop cones, rub them between your palms to crush the lupulin  glands and heat up the aromatic oils, then smell the hops and try to imagine what they would add to your beer.

Hop Hands

Kevin Somerville, Brewmaster Program Coordinator, dove right into hop nosing.

Hop resins are sticky, so pretty soon our hands were green, and we had flecks of hops sticking to our hair, clothes, faces, and shoes. Despite the “I showered in hop cones tonight” look, I found the nosing very interesting–who knew that UK Fuggles (earthy, woody) would smell so different from US Fuggles (citrus)? Or that Cascade, once the darling of the American hop; industry, was now “so 2008” as new and more muscular hop varieties made their way onto the world stage.

We had been invited to take away samples in small baggies, and it was interesting to see which varieties were a big hit–the container of Apollo was empty by the end of the evening.

I left with several samples as well; luckily I was not pulled over during the drive home while carrying several baggies of fresh aromatic green plant material.

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