Author: Will Lovell
Of the various off-flavors that can plague beer, oxidation is viewed by many as being one of the more pesky, as it can occur at various points in the process, and once it’s there, good luck getting rid of it. While brewers have developed a number of manual methods for reducing the risk of cold-side oxidation, some have adopted the use of chemicals known to scrub oxygen from beer before it has a deleterious effect.
Sulfites are a commonly known chemical antioxidant that, when added to beer, creates a strong reducing agent that leads to a redox reaction. Another chemical antioxidant that has been getting increased attention is ascorbic acid, or vitamin C, which is preferred by some brewers as it does not contain sulfites and hence poses less risk to consumers.
Similar to sulfites, ascorbic acid has been widely used as an effective means of preventing oxidation in wine, though only recently seems to have gained acceptance among brewers. Having personally experienced the benefits sulfites can have on reducing oxidation in beer, I was curious to see what impact ascorbic acid might have and designed an xBmt to test it out.
| PURPOSE |
To evaluate the differences between a West Coast Pilsner where ascorbic acid was added at packaging and one that was not dosed with ascorbic acid.
| METHODS |
Combining delicate malt with moderate hopping, I went with a West Coast Pilsner recipe for this xBmt.
Fairly Convinced It’s An Actual Style
Recipe Details
| Batch Size | Boil Time | IBU | SRM | Est. OG | Est. FG | ABV |
|---|---|---|---|---|---|---|
| 5.5 gal | 60 min | 38.2 | 4.4 SRM | 1.05 | 1.011 | 5.12 % |
| Actuals | 1.05 | 1.011 | 5.12 % | |||
Fermentables
| Name | Amount | % |
|---|---|---|
| Llano Pilsner | 10.5 lbs | 91.3 |
| Denton County Wheat Malt | 12 oz | 6.52 |
| Victory Malt | 4 oz | 2.17 |
Hops
| Name | Amount | Time | Use | Form | Alpha % |
|---|---|---|---|---|---|
| Magnum | 9 g | 60 min | Boil | Pellet | 12 |
| Mosaic | 25 g | 15 min | Boil | Pellet | 11.6 |
| Amarillo Lupomax | 45 g | 1 min | Boil | Pellet | 14.5 |
| Citra | 45 g | 1 min | Boil | Pellet | 12 |
| Centennial | 30 g | 1 min | Boil | Pellet | 9.2 |
| Amarillo Lupomax | 30 g | 3 days | Dry Hop | Pellet | 14.5 |
| Centennial | 30 g | 3 days | Dry Hop | Pellet | 9.2 |
| Citra Lupomax | 30 g | 3 days | Dry Hop | Pellet | 18 |
| Mosaic | 28 g | 3 days | Dry Hop | Pellet | 13.1 |
Yeast
| Name | Lab | Attenuation | Temperature |
|---|---|---|---|
| Global (L13) | Imperial Yeast | 77% | 46°F - 55.9°F |
Notes
| Water Profile: Ca 69 | Mg 10 | Na 0 | SO4 117 | Cl 66 |
Download
| Download this recipe's BeerXML file |
After collecting the water for a single batch, adjusting it to my desired profile, and setting my Delta Brewing Systems AIO controller to heat it up, I weighed out and milled the grains.
When the water was properly heated, I incorporated the grains then checked to ensure it was at my target mash temperature.
During the mash rest, I prepared the kettle hop additions.
Once the 60 minute mash was complete, I removed the grains and proceeded to boil the wort for 60 minutes, adding hops at the times stated in the recipe.
When the boil was finished, I quickly chilled the wort before taking a refractometer reading that showed it was at the expected OG.
After transferring the wort to a sanitized Kegmenter, I direct pitched a single pouch of Imperial Yeast L13 Global and left it to ferment at 64°F/18°C.
With all visible signs of fermentation absent after 1 week, I took a hydrometer measurement showing FG had been reached.
At this point, I cold crashed the beer to 35°F/2°C, returning 24 hours later to prepare for packaging. Seeing as ascorbic acid is used to mitigate cold-side oxidation, I opted to forgo my regular process of purging the kegs with CO2 and added 0.5 tsp/2.7 g of ascorbic acid to one keg while the other received nothing.
I then transferred 2.5 gallons/9.5 liters of beer to each keg before placing them on gas in my keezer. After 3 weeks of conditioning, the beers were carbonated and ready for evaluation, though both maintained a similar haziness.
| RESULTS |
A total of 21 people of varying levels of experience participated in this xBmt. Each participant was served 2 samples of the non-dosed beer and 1 sample of the beer dosed with ascorbic acid at packaging in different colored opaque cups then asked to identify the unique sample. While 12 tasters (p<0.05) would have had to accurately identify the unique sample in order to reach statistical significance, only 8 did (p=0.40), indicating participants in this xBmt were unable to reliably distinguish a West Coast Pilsner that was not dosed with ascorbic acid at packaging from one that was dosed with ascorbic acid at packaging.
My Impressions: Out of the 5 semi-blind triangle tests I attempted, I correctly identified the odd-beer-out just twice. I perceived both of these beers as having a slightly stale flavor with muted hops, and while they weren’t awful, these are characteristics I associate with oxidation.
| DISCUSSION |
As the name implies, off-flavors are undesirable in beer and turn what was intended to be deliciously refreshing into an undrinkable mess. While oxidation has always been a concern of brewers, it’s received a bit more attention lately due to the negative impact it has on hoppy styles, and one method for combating this beer ruining off-flavor is through the use of chemical antioxidants such as ascorbic acid. Interestingly, tasters in this xBmt were unable to reliably distinguish a West Coast Pilsner that was not dosed with ascorbic acid at packaging from one that was dosed with ascorbic acid at packaging.
Considering these beers were transferred to kegs that were not first purged with CO2, both were ostensibly exposed to similar amounts of oxygen, and the fact they were indistinguishable to tasters suggests the ascorbic acid had little to no impact. While this could be an indication that neither was oxidized, my own assessment of these beers aligned with post-survey feedback from tasters – both possessed the tell-tale signs of oxidation. Given the results from numerous past xBmts demonstrating the effectiveness of sulfites for oxidation mitigation, the findings from this xBmt suggest ascorbic acid may not be as efficacious.
I loathe oxidation and will do whatever is necessary to ensure its absence in my beer including chemical methods. Sulfites have consistently been shown to reduce the negative impact of cold-side oxygen exposure, but understanding that some people are allergic to these compounds, I was hopeful ascorbic acid would have a similar effect. Unfortunately, that wasn’t the case in this xBmt, and both beers ended up possessing what I perceive as oxidation off-flavors. As a known antioxidant, I’m left wondering if perhaps the amount of oxygen exposure was simply too much for the ascorbic acid to handle, and while I look forward to further exploring it, I’ll continue employing the methods that have worked for me, which has included the use of sulfites.
If you have any thoughts about this xBmt, please do not hesitate to share in the comments section below!
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16 thoughts on “exBEERiment | Cold-Side Oxidation: Impact Adding Ascorbic Acid At Packaging Has On A West Coast Pilsner”
Any plans to test Ascorbic acid during the mash as an antioxidant?
Yes I think the mash experiment would be interesting. Oxidation starts way earlier than packaging. It would be interesting to see the difference of using it the way this experiment was conducted vs adding the ascorbic acid during the mash.
I’ve used small amounts in the mash and have notice a better colour and flavour in NEIPA. While I use ascorbic acid, I still do a lot of the other LODO practices. Ferment under pressure, transfer under pressure to purged kegs, etc.
Great experiment. I will continue to use a carbonation stone in my receiving keg bottom (set at 8-10 psi) to fill my kegs when I auto-syphon my beer. Keep on researching for the final solution to maintain all the goodness we expect when we package our products! Brew on!
I use ASCORBIC ACID all the time when brewing and it works. Wery popular among swedish homebrewers
I’m glad it works for you. In this xBmt it didn’t seem to have the desired effect. SMB or KMB seems to work better in my experience.
3 weeks? Not 3 months?
All xBmts have to start somewhere, but since both beers were oxidized at 3 weeks, I’m not entirely sure what 3 months would have accomplished.
Perhaps this was just mission impossible for 2.7g of ascorbic acid vs 2.5 gal of air in the keg headspace. Would this not be more instructive a test with fully filled but not purged kegs…?
The article didn’t specify, but I used two smaller kegs. There was a normal amount of headspace typical of kegging. I did not purge that space.
It’s my understanding ascorbic acid needs to be used in conjunction with metabisulfite or otherwise it can have pro-oxidative effects.
Would love to see the source on this. Instructions just said add it at packaging.
This is regarding research in wine:
“Ascorbic acid sometimes protects the fruit and acts as an antioxidant, while at other times it can act as a proto-oxidant, or oxidative promoter. The two roles of ascorbic acid are mainly the result of concentration and the presence of adequate sulfur dioxide. When ascorbic acid is added to wine, it binds oxygen rapidly to form two reaction products, dehydroascorbate and hydrogen peroxide. If there is not enough ascorbic acid maintained to react with the oxygen, oxidative degradation, including coupled oxidation, can occur. If there is not adequate sulfur dioxide maintained to bind with the hydrogen peroxide formed by the ascorbic acid, wine oxidation can occur. The reaction between ascorbic acid and oxygen is much more rapid than with SO2.”
https://brewingforward.com/wiki/Ascorbic_acid
Based off of this, its related mostly to wine, so hard to say if this does, or doesn’t, correlate to beer. I’m honestly not smart enough to know. I just went off the package directions that said to add it at packaging (instructions did not say to add sulfites). Since KMB and SMB both came back significant, it seems it may be worth exploring if there is much, if any, added benefit to adding AA to that mix or not. That might be a difficult test to design however.
Hey Marshall,
My wife and I have had great success with ascorbic acid in our brews. We keg and closed transfer into a purged keg, and we haven’t had any issues with cold side oxidation since we started using it. While we haven’t done a side-by-side, we have noted a distinct lack of oxidation comments in our judged beers. In fact, our double-decocted Munich Dunkel took best of show and we used ascorbic acid in it.
As per the Genus Brewing recommendation, we add 1 tsp into a 5 gal batch to the mash at the beginning. See the Genus Brewing podcast video, link below. It would be interesting however to see if the elevated temperature is the key to getting success with it.
Cheers!
Matt and Sarah
https://youtu.be/vriDv0XrJj0?feature=shared
I’ve always used it in the mash, as that’s what some other folks have advised me to do. I don’t think I’ve ever had an oxidation issue that way, but I’ve not done a side by side. That said, I think lots of folks add it at the mash rather than at packaging.
It can be used for both. Since the directions on the package advised use at packaging, that was where we started.