Author: Jake Huolihan

Oxidation of beer occurring once fermentation is complete is known to hinder shelf stability and lead to undesirable off-flavors. When fermented beer comes into contact with oxygen, often during the packaging process, it reacts with various carbonyl compounds that get converted to other compounds tasters can perceive as stale, cardboard-like, and unpleasantly sweet. Good commercial brewers invest quite a bit of effort to prevent their beer from being exposed to oxygen, usually involving cumbersome and expensive equipment that significantly limits total oxygen in the packaged beer.

Most homebrewers don’t have access to equipment like this and have to rely on more rudimentary methods for reducing post-fermentation oxidation. While cold crashing with CO2 filled balloons in place of an airlock and purging kegs prior to filling have been shown to have some effect, these methods do little to remove whatever small amount of oxygen might end up in the actual beer. This is where a chemical called sodium metabisulfite (SMB) comes into play.

Often sold in the form of Campden tablets, SMB releases sulfur dioxide when added to beer, turning it into a strong reducing agent that initiates a redox reaction. To put it simply– adding SMB to beer will fairly rapidly lead to lower levels of dissolved oxygen. Sulfites have a long history of use in the wine and juice industries, but it’s essentially absent in commercial brewing, perhaps due to the fact government regulations require disclosing its use on packaging. Exempt from such regulations, homebrewers have begun experimenting with using sulfites at various points in the brewing process to improve flavor stability. Inspired by a recent chat with Dr. Charlie Bamforth, I was curious to see what impact adding SMB to beer at packaging has and put it to the test!

| PURPOSE |

To evaluate the differences between a beer dosed with sodium metabisulfite at packaging and the same beer packaged without the chemical.

| METHODS |

I decided to brew a Kölsch for this xBmt, as its simple enough to allow any subtle differences to shine.

Preservation

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 40.3 IBUs 4.0 SRM 1.051 1.012 5.2 % Actuals 1.051 1.012 5.1 % Fermentables Name Amount % Odyssey Pilsner 11.25 lbs 97.83 Carahell 4 oz 2.17 Hops Name Amount Time Use Form Alpha % Perle 23 g 60 min Boil Pellet 8 Perle 25 g 25 min Boil Pellet 8 Yeast Name Lab Attenuation Temperature Dieter (G03) Imperial Yeast 75% 60°F - 69°F Notes Water Profile: Ca 65 | Mg 0 | Na 8 | SO4 67 | Cl 68 Download Download this recipe's BeerXML file

While collecting the brewing liquor the night before brewing, I weighed out and milled the grain.

After adjusting the water to my desired profile, I dropped my heat stick in and scheduled it to turn on early the next morning.

I woke up to hot liquor the next morning and immediately mashed in, checking to ensure I hit my target mash temperature.

The mash was left to rest for 60 minutes.

At this point, I weighed out the kettle hops.

When the mash was complete, I collected the sweet wort in my single boil kettle and brought it up to a boil.

Following a 60 minute boil, I quickly chilled the wort.

A refractometer reading showed the wort was right at my planned OG.

The wort was split evenly between two sanitized Brew Buckets, which I connected to my glycol system set to maintain a fermentation temperature of 62°F/17°C. I then direct pitched a pouch of Imperial Yeast G03 Dieter into each batch.

After 3 days of active fermentation, I began raising the temperature of each vessel to 66°F/19°C. With signs of fermentation absent after 13 days, it was time to introduce the variable and package the beers. To scrub the oxygen from 5 gallons/19 liters of beer, it’s recommended to add 10 ppm SMB, which amounted to only 0.3 grams (1 gram SMB = 175 ppm/gallon). Strong stuff.

After sanitizing and purging a keg with CO2, I gently added the small amount of SMB, sealed the keg, and purged it again. The keg of the batch without SMB was also purged with CO2 prior to kegging.

The filled kegs were placed in my keezer on gas and allowed to condition for 6 weeks prior to serving, as I wanted to allow enough time for any impact of oxygen exposure to occur.

| RESULTS |

A total of 22 people of varying levels of experience participated in this xBmt. Each participant was served 2 samples of the beer packaged without SMB and 1 sample of the beer packaged with SMB in different colored opaque cups then asked to identify the unique sample. A total of 12 tasters (p<0.05) would have had to accurately identify the unique sample in order to reach statistical significance, which is exactly how many did (p=0.033), indicating participants in this xBmt were able to reliably distinguish a Kölsch packaged with SMB from one packaged without the preservative.

The 12 participants who made the accurate selection on the triangle test were instructed to complete a brief preference survey comparing only the beers that were different. A total of 5 tasters reported preferring the beer packaged with SMB, another 5 liked the beer packaged without SMB more, and 2 people reported no preference despite perceiving a difference.

My Impressions: Out of the 5 blind triangle tests I attempted, I easily selected the odd-beer-out every time based on aroma alone, though I perceived differences in flavor as well. To me, the beer kegged without SMB had a distinct smell that was reminiscent of Golden Grahams cereal– biscuity and slightly sweet. This characteristic was completely absent in the beer kegged with SMB, which I perceived as having a cleaner Pilsner malt character. While both beers were good, my preference went to the one packaged with SMB.

| DISCUSSION |

It’s well known that oxygen is an enemy to beer, hastening the staling process and turning good beer bad. While most brewers rely on methods of oxygen reduction that involve cumbersome and expensive machines, a seemingly simpler though much less popular option is to add sodium metabisulfite (SMB), a compound that reacts with beer to remove oxygen. The fact tasters in this xBmt were capable of reliably telling apart a beer kegged with SMB from one kegged without the substance seems to suggest it does have an impact.

In addition to reducing the risk of oxidation, SMB also hinders the growth of spoilage microbes like wild yeast and bacteria, which may lead one to wonder why it’s so rarely used in the brewing industry. Claims that sulfites lead to headaches have been debunked, and while higher amounts have been shown to cause respiratory issues, the levels present in beverages treated at the proper rates are low enough to be a non-issue. Perhaps there’s a stigma associated with the use of “chemicals” in beer, similar to the way people fear GMO.

Given its apparent oxygen sensitivity, I’m curious to explore the impact this method has extending freshness of NEIPA, and I also plan to look into whether a small dose of SMB might be able to replace the process of purging kegs with oxygen. Regardless, I prefer fresh beer and have zero concerns about the minuscule amount of sulfite present when using SMB at packaging. With the results of this xBmt backing up my personal experience with the beers, which I was initially skeptical about, I absolutely plan to make packaging with SMB a normal part of my process.

If you have any thoughts about this xBmt, please do not hesitate to share in the comments section below!

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