Many professional brewers will tell you that the #1 shortcoming of homebrewed beers is oxidation.  Oxygen ingress, even in small amounts can spoil your beer, adversely affecting its flavor, clarity and shelf-life. When homebrewing, harmful oxygen is most often introduced after fermentation is completed. Opportunities to introduce unwanted oxygen occur when taking hydrometer readings, transferring to secondary vessels, dry hopping, when cold crashing and during packaging.

Inventive  homebrewers have developed a variety process changes, methods and tools to limit oxygen in their beers. During my years homebrewing I’ve adopted several methods to reduce oxygen ingress in my beers. These include ending my use of secondary fermentation (except when steeping flavor additions like fruit) and kegging instead of bottling my beer. Like many homebrewers I’ve struggled finding ways to reduce oxygen exposure at the end of fermentation. At this stage of the brewing process, I’ve taken steps to blow CO2 into my fermentation vessel headspace following each time the vessel is opened in an attempt to purge as much oxygen as possible. I’m not sure how effective this action is, but it not only makes some sense but it also makes me feel better. 

Cold Crashing Challenges

As we discussed earlier, cold cashing is another time when oxygen ingress can be high. When cold crashing your beer, the reduction in temperature in your sealed fermentor creates a vacuum effect that pulls outside air (and fluids) in through your airlock. Like many homebrewers, I’m concerned with how much oxygen is getting into my beer during this time. I’m also not comfortable with pulling in sanitizer from my airlock. Sanitizer isn’t harmful, but I still don’t want it in my finishing beer.

As homebrewers have become more aware of oxygen and sanitizer ingress during cold crashing, they have “gerry-rigged” a wide range of solutions. Many of those solutions involve capturing CO2 during fermentation using tubing and balloons. Once cold crashing begins, the captured CO2 is then sucked back into the vessel in an attempt to avoid oxygen ingress.

“Cold Crash Guardian”

The inventive engineers at BrewHardware.com have come up with a creative and relatively inexpensive solution to the problems of both oxygen and sanitizer ingress during the cold crash. Their product is appropriately called the “Cold Crash Guardian – No Oxygen Cold Crash Blowoff” (I tested version 3, small size). According to their website, I’m considered an “early adopter” since they are cautiously rolling out the product so they can gather customer feedback before making its availability more widespread. Their website has a detailed product description and a very helpful video to explain the need for the product and how it works.

At $18 I decided to give it a try. The product is available in two sizes, 2.5 gallons (for batches from 3 to 10 gallons) and 1 gallon (for batches up to 3 gallons). Your purchase includes the expandable bladder to capture fermentation CO2, a nylon double sided 3/8” hose barb (connects to the fermentor grommet or carboy cap), a barbed one way check valve, a 3/8”hose barb tee (nylon or stainless depending on availability) and 3 feet of 3/8” ID PVC tubing to connect everything. 

When assembled, you have a hose barb with attached hose coming from your fermentor grommet or carboy cap, that then runs to the hose barb tee. At the tee, hoses then run in two directions; one to the valved bladder and another hose to a one-way check valve. An additional section of hose is added to one end of the check value to connect to a jar of sanitizer. This hose section serves as a fermentation blow-off hose.

Here’s How It Works…

The good folks at brewhardware.com suggest starting your fermentation with a standard blow-off  hose to avoid getting fermenting blow-off debris in the Guardian apparatus. After you are sure your fermentation has peaked, connect the Cold Crash Guardian to the fermenter. Be sure the bladder is fully deflated with the bag value lever closed. Allow some time for the fermentation CO2 to pass the system fully to purge any air in the lines. Next, open the bladder valve. The bladder will soon begin to fill and inflate with CO2 from your fermenter. Once the bladder is full, any excess CO2 will be vented through the one way check valve resting in the sanitizer jar. You’ll be able to see this excess CO2 as bubbling in your sanitizer.

Once fermentation is complete and you begin your cold crash, a vacuum will be created by the cooling fermenter. This vacuum will draw the CO2 from the Cold Crash Guardian bladder into your beer. Because of the one way check valve, no sanitizer will be drawn back into the fermentor. Only CO2, no oxygen, sanitizer or bacteria will be drawn back into your beer! How cool is that?!?

My Experiences Using the Product

Initially assembling the Cold Crash Guardian was a challenge. The issue was with the double sided 3/8” hose barb fitting that connects to the fermenter. The angle and depth of this fitting was too short to reach the port in my carboy stopper. I use a stopper with a recessed edge, and the fitting was just not long enough to reach down to the port. Fortunately the remedy was pretty simple. I was able to locate a straight 3/8’ double sided barb fitting in the plumbing section at my local hardware store. For $0.71 the problem was solved.

 I decided to try out the Guardian to brew a lager. Since I rarely experience a fermentation that is vigorous enough to require a blow-off tube, I went ahead and just connected the Guardian system. After careful consideration, I decided to open the bladder bag from the start to capture CO2 from the early fermentation. Since the yeast strain I was using tends to produce some sulfur later in the fermentation, I was hoping to capture the sulfur-free CO2 from the initial fermentation.  Once the bladder was full, I closed the bladder bag for the rest of the fermentation. This successfully allowed me to capture sulfur-free CO2.

The bladder valve seemed to be another area for product improvement. It was a little difficult to determine when the valve was fully closed or open. It could be improved by offering a clear open and closed position. 

The product performed as the manufacturer claimed throughout the fermentation. The one-way valve worked quite well allowing excess CO2 to vent through the blow off tube in the sanitizer. The bladder bag filled fully during the early fermentation and I noticed no leaks or deflation once the bladder valve was closed. One thing homebrewers will need to remember is to close the bladder bag valve anytime they open their fermentor to conduct activities, like taking hydrometer readings. If a brewer forgets to close the bladder bag first, some or all of the captured CO2 might escape.

Since I am concerned with oxygen ingress, I try to open my fermentor only when necessary and for as short a time as possible. I tend to blow off my fermentor headspace with CO2 whenever I open it in hopes of limiting my beer’s exposure to oxygen. For purposes of this system test, I decided to forego that practice for this batch of beer. 

Consistent with the instructions, I opened the bladder bag value once the cold crashing began for my lager. The Guardian again worked as the manufacturer promised. I was a little difficult to determine how well it worked since the CO2 sucked back from the bag was pretty minor for my 3 gallon batch. The bladder definitely deflated some, but I was surprised by how little it was. The one-way valve also did its job by preventing any sanitizer from being sucked back into the fermenter. 

All in all, I was pleased with the performance of the Cold Crash Guardian. It worked as advertised by successfully keeping oxygen, sanitizer and bacteria from my beer during cold crashing. With a couple of minor improvements, I think this product will prove very popular and useful to homebrewers. At just $18, this is a very affordable solution to a problem that has concerned homebrewers for several years. Brewers of NEIPAs will find this to be a valuable tool in their efforts to limit the damaging effect of oxygen ingress. 

If you have any questions or comments, please use the comments section below. Prost!