Wort Chilling

Wort Chilling
by Sammy Samoluk
(this article first appeared in the December 1999 issue of the Home Imbrewment)

After you’ve boiled a kettle of wort there are many ways to get your wort to a temperature low enough so that it won't cook your yeast. In this article, I wish to present some thoughts on why it might be better to do so as quickly as possible. I also offer some ideas on how to make wort chillers, and sensible ways to use them.

When you're brewing a concentrated wort on the stove top and diluting with cool water to achieve a final volume, chilling the wort is a fairly simple proposition. To stack the deck in my favor, I used to put two gallon jugs of previously-boiled and cooled water in the freezer before brewing. Then I'd place my brew pot in a sink filled with ice water, and after the wort stopped steaming, I’d mix my two cold jugs of water with my three gallons of concentrate from the brew pot to fill my
carboy. Once I started boiling the entire wort, however, I found that ten or even five gallons of boiling liquid takes a heck of a long time to cool to room temperature on its own. Then I learned about wort chillers.

Why chill the wort? Most importantly, rapid cooling and pitching of yeast gets the friendly flora multiplying in the wort before competing wild organisms have a chance to take hold, and the resultant alcohol produced further safeguards the batch from infection. Secondly, rapid cooling facilitates the 'cold break', during which proteins coagulate and drop out of solution. A good cold break can help minimize chill haze in the final product. Also, commercial brewers have found that the flavor of ales benefits from separating the wort from the cold break trub (pronounced 'troob', it's the protein sludge that falls to the bottom of the fermenter). Oddly enough, the same does not seem to hold true for lagers.

There's a third reason that’s important to me, but has not been mentioned in any of the articles I've read on the subject, and that is the solubility of oxygen in the wort. As you know, the lower the temperature of a liquid, the more gas can be dissolved into it. Those who force-carbonate with pressurized CO2 use this principle when conditioning their finished beer, and the principle is no less important when aerating the wort at the start of fermentation. The amount of oxygen you
can get into your wort after cooling will directly affect the number of healthy yeast cells working for you. In a nutshell, the yeast store oxygen in their cell walls in the form of glycogen. If a healthy cell starts out with the maximum amount of glycogen in its cell wall, it can divide no more than three times before the glycogen levels are at minimum acceptable. Introducing oxygen later in the process will promote staling of the beer and cardboard off-flavors, so all usable oxygen needs to shaken, beat or bubbled into the wort before fermentation.

Recognizing that it's beneficial to chill your wort after the boil, how will you go about chilling a large volume of boiling liquid? There are essentially two types of chillers to be made or purchased: immersion or counterflow. The simplest is the immersion type. It consists of about 30 feet of soft copper tube bent into a coil of about one foot diameter. Cool tap water courses through the coil and carries out the heat you put into the wort. Efficiency will depend on the season. In winter,
the 48 degree Norfolk city water works much quicker than the 75-degree summer water temperature.

Some procedural tips will help. First, ensure all of your water connections are tight. You don't want to spray cooling water into your wort, or worse yet, douse yourself with scalding outflowing water. Make no mistake here: the initial cooling water will exit the chiller near the boiling point, so be careful what you do with it. For most efficient chilling, suspend your chiller near the top of the wort, so the chilled, more dense wort will fall to the bottom of the kettle, creating a natural
circulation. Ensure that the water enters at the top of the coil, where the wort is hottest, and spirals down toward the bottom of the kettle. The immersion chiller will be much more efficient and effective if you stir the wort at least occasionally. Finally, throttle the flow rate of the cooling water to get the most cooling action out of your chill water. Start out with a slow trickle, and as the wort temperature in the kettle approaches the chill water inlet temperature, increase flow rate to
maximize the temperature difference between the coil and the wort.

As an environmentally conscious (and penny-pinching) brewer, you don't want to waste water, so what do you do with the perfectly good water gushing from the outlet hose of your immersion chiller? I use the first and hottest outflow to sanitize the interior of a second stage counter-flow type chiller. Then, I catch all outflow in a fermentation bucket, and this I put to use around the house. I dump the hottest water into the washing machine. Add soap and whites, and when you turn on
the machine, it will sense the water level and skip the fill cycle. I have also used it to fill inflatable kids' pools with warm water, and I always keep some warm water for cleaning up my brewing equipment when I'm done. I have even connected the outflow hose to a lawn sprinkler to get the same effect as an industrial cooling tower, while also watering the grass and garden. Not a drop of precious water is wasted.

Making an immersion chiller is easy. Simply pick up at least 30 feet of soft copper tube from your favorite hardware or home improvement store. While you're at it, pick up the spring tool which slides over the tubing to prevent crimping. It only costs a few bucks, and comes in handy for the four 90-degree bends you will make. The hose bends easily by hand. Here is my recommended technique:

Start with a 90-degree bend about three inches from one end. This is the water inlet end. Then, with the three-inch section resting on the pot rim, let the tube run straight down until it would reach the top of the wort level in your pot or kettle. Then make another 90-degree bend to parallel the surface of the liquid, slightly submerged. Next, bend the tube into a coil of a diameter a few inches smaller than that of the brew pot. You want wort to be able to flow around all sides of the
coil. Keep spiraling down, and when you've completed six or eight loops in the coil, you should have only a few feet remaining. Make one 90-degree bend straight up, and another so that the tube hangs on the pot rim. Then select your end fittings.

Your helpful hardware man can assist with the specifics, but you have three basic options for connecting water in and out. The easiest is to jam some aquarium hose on the ends of the chiller and secure it with hose clamps. On the other end of the aquarium hose, install an adapter for your water source, be it the kitchen sink or an outdoor spigot or bib. A more elegant method is to put a compression fitting on the end of the tube, then get a tube-to-hose adapter (or series of adapters).
Then you can screw a garden hose directly into the inlet of the chiller. This method, like the previous one, requires no special tools. The most elegant solution, however, is to get a flare-to-hose adapter. This method also allows connection of a garden hose directly to the chiller inlet. It requires a flare tool, but you save on adapters and end up with a cool tool to show for it.

Immersion chillers don’t require extensive cleaning and sanitization. Simply put the coil into the kettle for at least the last 15 minutes of the boil, and it will be sanitized.

Since this article is already twice as long as it should be, I won’t cover counter-flow chillers, but suffice it to say that they are very efficient and very cool in their own right! I will be glad to assist any club member with the fabrication of wort chillers. I will gladly loan out my flare tool and tube bender. Wort chillers are well worth the investment, easy to use, shorten the brewing day, and make better beer. Next time: "Integrating Your Brewing Equipment." Enjoy!

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