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Using a Corny For Primary, The Need for Sterilizing and Uses for a Spare Fridge

Q I want to ferment under pressure at 65–70 °F (18–21 °C) in a 5-gallon (19-L) Corny keg using a spunding valve set to 10–12 psi. My plan is to boil the wort, whirlpool the heck out of it to get the trub into the center of the kettle, then pump it directly into the corny keg, purge out the oxygen with CO2 and put it under light pressure. leave it to cool overnight and then pitch the yeast. Exactly what are the potential problems with this, if there are any?

Idar Hoydal
Oslo, Norway

A There are a few possible problems with this plan, but none are insurmountable. What you are describing is something akin to coolships that were ubiquitously used by lager and ale brewers before better types of coolers were used. Even after the development of modern wort cooling using plate coolers, some lager brewers continue to use settling tanks and flotation tanks to remove cold break from wort before fermentation. I will come back to this in a moment, but want to quickly point out the issues presented by your proposed method.

Problem #1. Cooling hot wort in a closed container can lead to the conversion of SMM (S-methylmethionine), the DMS (dimethyl sulfide) precursor, into DMS. The problem with DMS is that it can lend a vegetal, cooked-corn aroma to beer, especially lighter styles with low flavor profiles brewed from lightly kilned malt that normally contains more SMM than more highly kilned malts. I think this problem is often overblown by homebrewers who read journals and textbooks targeted to commercial brewing because small batches of hot wort tend to cool below 176 °F (80 °C) relatively quickly due to the high surface-to-volume ratio of small containers.

A Corny keg has many advantages when used as a fermenter, but certain steps should be taken to ensure success. Photo by Mick Spencer

Your closed keg of wort will likely cool below this temperature, which is considered the minimum required to convert SMM into DMS. But to err on the cautious side, consider putting your keg in a bucket of water and slowly running water into the bottom of the bucket and allowing the hot water to spill from the top. Gently rocking the keg during this process will speed things up. Monitoring the exterior surface temperature of the keg is an easy way to determine when you have cooled it enough to stop the water process and to allow the air cooling to take over.

Problem #2. Assuming that your batch size is 5 gallons (19 L), fermenting in a Corny keg is going to result in considerable beer loss because beer still foams when it ferments under pressure after equilibrium at the spunding valve set-pressure is met and excess carbon dioxide is produced. There are several options to this dilemma, including reducing the fill volume to about 4 gallons (15 L), using an anti-foaming agent like Fermcap-S, and conducting the primary fermentation in a larger fermenter and racking to the keg once the fermentation begins to slow. If using an anti-foaming agent, it is important to remove before packaging because these brewing aids do a great job of preventing beer from foaming. This can be accomplished by simply racking the beer to another vessel. However, once removed there is no residual activity and beer foam stability is not adversely affected; in fact, it is often better than in beer without anti-foam, but that’s a topic for another day.

Problem #3. The best way to remove cold-break trub is after wort cooling. Your proposed method only removes hot break from your wort in the whirlpool. Consider adding a kettle coagulant like Irish moss or a purified carrageenan from farm-raised, warm water seaweeds (e.g., Euchema cottonii) like Whirlfloc to increase the formation of cold-break material. The aforementioned settling and flotation tanks are both used to remove cold break from wort prior to pitching.

Settling simply involves time while flotation relies on nitrogen from wort aeration to float cold trub to the wort surface where it can be skimmed or left in the tank following wort removal from the bottom. Settling works great for hot wort cooled in place while flotation should only be used following wort cooling and aeration because aerating hot wort causes wort darkening and does not dissolve sufficient oxygen for the benefit of our brewer’s yeast.

Problem #4. Your method omits wort aeration. This is not a problem if you are using dried yeast because those little critters are packed full of sterols and glycogen from how they are grown prior to drying, but liquid cultures do require wort oxygen for cell division.

Here is a proposed alternative method aimed at removing the trub:

  1. Add a kettle coagulant at the end of the boil to help your trub compactness when whirlpooling and to precipitate cold break during cooling.
  2. Transfer the wort to a carboy (plastic or glass), attach an S-style airlock, and jam a cotton plug in the open end of the airlock. Cotton plugs are very effective and inexpensive air filters and the plug will remove airborne contaminants from the air that will be pulled through the S-style airlock as the wort cools. Do not use a 3-piece airlock because this style does not prevent suck-back. What is fun is watching cold break form and settle. One reason for using a carboy is to allow for visualization of process.
  3. After about 8 hours, your wort should be cool and cold break should be settled in the carboy.
  4. Rack to your fermenter, aerate if needed, pitch yeast.
  5. If using something other than your Corny keg, rack from your primary to your Corny with a spunding valve set up when your fermentation is about 70% complete. There will be plenty of yeast in the fermenting beer to finish the job and the fermentation rate will have slowed to minimize foam formation and foam spittle from the spunding valve.

The other option is not to worry about removing the cold break before fermentation and to go ahead as you propose, but with a partial fill (roughly 4 gal./15 L) of your keg.

Q I’m enjoying your videos on BYO+ and have a follow-up question on dry hopping. I dry hop using a steel mesh ball that works really well. My method is to sterilize the ball, string, etc. before adding to the fermenter (about 4–7 days prior to kegging). Is this overkill due to the anti-microbial effect of hops (potential imparting of cleaning chemicals into the beer)? Can I skip the sanitize step as long as I ensure everything is clean?

Dirk Megarry
Biwabik, Minnesota

A This question is timely; the last time I brewed I was daydreaming about the necessity of sanitizing everything that touches beer after wort cooling because the use of sanitizers is relatively new in the history of beer. Sure, there was a lot of sour and spoiled beer before the introduction of modern hygienic practice, but all beer was not some sort of train wreck that was generally unenjoyable. I know there are brewers reading this thinking “duh, everyone knows that everything that even looks at wort after cooling must be sanitized!” Yet brewers add all sorts of things to beer during and after fermentation.

Dry hops, fruit, gases, finings, anti-foams, foaming agents, hop extracts, and stabilizers are a few examples. In commercial breweries, the beer is finally filled into some sort of package. The largest volume of beer is filled into bottles and cans before a bottle or can lid is applied. These last two examples are common sources of microbial contaminants because microbes grow on crowning heads and can seamers during long production runs when yeast and bacteria, either from beer or the environment, multiply and contaminate packages. In short, you ask a great question about the requirement to sanitize these doodads, let’s just call them tools, used to contain and suspend your hop ball during dry hopping.

The first opinion I will offer is that relying on the antimicrobial properties of hops to safeguard beer against spoilage is not a great strategy because beer spoils! Ergo, the bugs that spoil beer must not be particularly sensitive to hop acids. Dry hopping, however, is not typically implicated with beer spoilage because the microbes that grow on hops are not the sort that spoil beer. Call it serendipity or divine intervention, fans of dry hopping dodged a bullet with that one. However, just because hops have antimicrobial properties and are not commonly associated with beer spoilage does not lead this brewer to conclude that taking normal precautions when putting brewing tools in the fermenter should not be followed.

The long list of things above that are added to wort and beer serves as an example of ingredients and process aids that are oftentimes not chemically or thermally treated immediately, or sometimes ever, before use in the brewery. Reducing the number of items that can contaminate beer is a handy way of minimizing the number of things that can go awry when making beer. And in the modern world of brewing, the use of liquid sanitizers is an easy and effective means of accomplishing this goal.

I feel comfortable that I have provided sound and current brewing advice and can now jump into that rabbit hole about the necessity of using sanitizers. For starters, why are sanitizers the norm in commercial breweries? That’s easy; not all equipment can, with any reliable level of certainty, be freed of microbes during cleaning because of the number of hiding places where microbes can reside. Furthermore, the cleaning equipment itself can be a very effective spreader of spoilage microbes around the brewery. Typhoid Mary is infamous in medical history books, but there are few chapters devoted to the things that haunt the commercial brewer: Promiscuous pumps, haggard hoses, shredded valve seats, wonky welds, demon dead-legs, septic seals, checkered check-valves, and burly biofilms. There is a saying amongst commercial brewers that tunnel pasteurizers allow brewers to sleep at night. But what does any of this have to do with homebrewing? Well, not much because our tools are simpler, smaller, and don’t touch nearly as much beer as tools used in a commercial brewery.

The bottom line is that most of the brewing tools at home can be cleaned, rinsed, and used without any sort of chemical or thermal “kill step” because the soils that harbor spoilage bacteria and yeast can be removed by good cleaning practices. The big caveat here is that you must be thorough in your cleaning! The fun thing about experimenting with beer is that the worst thing that can happen is that a batch starts to funkify before it’s all consumed. Definitely not the end of the world. The same thing cannot be said for food handling where poor practices can directly cause severe illness. So if you decide to go au naturale and experiment with no sanitize brewing, let us know with a follow-up!

Q My neighbor recently gave me his used fridge and it still works great. I have been brewing awhile using all-grain ingredients. My question is, I can’t afford the next step in brewing, which for me is the Cornelius keg draft system. Is there any advantage using the fridge without the pressurized system?

Bill Uffmann
East Liberty, Ohio

A Glad to see you following one of the most important homebrewing rules of thumb; accept anything for free that can be used to further your pursuit of great beer! For what it’s worth, here are a few questions to consider when these great opportunities arise. If it doesn’t work, how much to repair? How much power does it consume and are the voltage, frequency, and total amp draw copacetic with what is available at home? Will it fit where it can be used? Does it look like it belongs at home or in a junkyard? Great that you hauled the fridge home before determining exactly what to do with it! Here are a few ideas:

Use #1 — Fermentation Control. The best use for a fridge, outside of the obvious beer cooler, is for fermentation control. A modest investment in a thermostatic controller allows one to convert a mundane refrigerator into the perfect temperature-controlled fermentation cellar. All you need to do is buy a controller, insert the temperature probe inside of the refrigerator, and plug the fridge into the controller. And if you buy a dual-purpose controller, you can plug the fridge into the cooling plug and some sort of heater, like heat tape wrapped around some sort of heat-conducting mass like a copper tube, into the heating plug. This project will run less than about $75. Just remember that if your free fridge has a freezer, this set-up will also turn the freezer on and off.

The best use for a fridge, outside of the obvious beer cooler, is for fermentation control.

Use #2 — Ingredient and Beer Storage. Brewing and party supply central. I don’t know about most folks, but my spouse does not want my brewing hobby or love of beer to take up room in our kitchen refrigerator. A second fridge is perfect for hops, yeast, great beers that all brewers require to stay current on brewing trends, homebrews that are chilling out waiting to be poured, and other brewing aids that need their own cool place to reside. Beer fridges are also perfect for adorning with cool, beer-related stickers, if that’s your jam.

Use #3 — Corny Kegerator. Cornelius keg layaway plan. The bill of materials required for a DIY project is short and will not break the bank if you do a little at a time. Start out by shopping for a used Corny keg that is in good shape. This is really not much of a challenge as these little gems are pretty easy to find for a reasonable price. The cool thing about Corny kegs is that a CO2 tank and regulator is not required for a keg to be useful. I will save the details about the uses for another time. A cobra-head tap, aka a picnic tap, is all you need to dispense beer from your keg once it’s time to spend a few more bucks; and a few bucks is literally all you need to spend.

Finally, there is a gas tank and regulator. This is the most expensive step and will run you about $150. Do not, I repeat do not, buy a used or really “good deal” on a gas bottle without knowing what you are getting into. Gas cylinders require periodic hydrostatic inspections and gas companies will not fill cylinders that don’t have current inspection certification. In fact, most gas companies will not fill cylinders outside of their “float” of tanks.

The best thing to do is to go into a local gas supplier, explain that you want to get set-up for a home system, and they will know what you need due to the number of brewers and beer enthusiasts with home dispense systems.

I know you stated that you cannot afford the next step right now. Just take my sage advice and make this a slow-to-develop project and invest in it over time. Minimizing the chore surrounding bottle washing, bottle filling, full-bottle storage, bottle rinsing, empty-bottle storage, and feeling like opening a bottle is just adding more work to the aforementioned tasks makes brewing at home so much more enjoyable! Packaging sucks and is the reason that most craft brewers dream of being able to sell all of their beer on draft.

Issue: March-April 2022