lodo w/SMB vs lodo w/AA
Posted: Sat Oct 22, 2016 9:55 am
Based on my brewtan b (BB) experiment, I confirmed for myself that simply attempting to prevent superoxides from forming is not adequate to protect against hot side oxidation (HSO). An active oxygen scavenger must be used on our scale and equipment. However, SMB can have negative side effects if the dose is too high, and, for me, it tastes out of place in ales. In fact, I don't believe ale strains are as efficient in managing sulfites as are lager strains. I can't back this in the literature, just my own experience. The next most commonly used antioxidant is ascorbic acid (AA), and there are even commercially available blends of SMB/AA that you can buy for brewing.
What intrigues me most about AA is that malt has a natural enzymatic system, ascorbic acid oxidase (AAO) and ascorbate peroxidase (AP) for utilizing AA to scavenge oxygen.
It would seem illogical to fail to take advantage of this built-in system, unless there were some negative side effects. In fact, there can be negative sides effects to using AA, mainly that the oxidized form of AA, dehydroascorbic acid (DHA), can in turn become an oxidizer itself. However, DHA generally has a very short half-life, and yeast also have the ability to convert DHA back to AA and use it for their own cellular metabolism. In theory, as long as you use AA upstream of fermentation, then the yeast should ensure that there are no AA or DHA remaining to negatively affect the finished beer. Studies have shown that AA is effective at preventing thiol, phenol and polyphenol oxidation during the mash. This is consistent with Tech's theory on phenols and their flavor contributions. Kunze speaks about the importance of specifically not oxidizing polyphenols during the mash and boil as well.
As a side note, citric acid (CA) is the most commonly used acid in lowering pH in sour beer production, and has its own antioxidant properties. Ironically, only one oxygen atom distinguishes citric acid from ascorbic acid. Both are readily available in fresh fruits to preserve and protect against oxygen degradation, and they are both likely present in sauergut. I need to investigate the composition of sauergut a little more, but based on the stability of the pH, redox potential and suite of microbes producing organic acids, it is very likely rich with oxygen scavenging organic acids. This blend of oxygen scavenging organic acids likely plays a significant role in sauerguts effectiveness in brewing, especially in combating HSO in the mash and boil.
I wanted to see if AA would be a direct substitute for SMB. I brewed up a third batch of helles (after the SMB and BB batches) to see if AA is a direct replacement for SMB. All other lodo practices were implemented, and the only variable was the the reagent. Both batches were brewed using:
1) pre-boiled strike and sparge water
2) underlet pumping for dough-in and subsequent transfer to BK
3) mash cap
4) copperless system
5) low boil (210-211F at the surface temp)
6) fast wort chilling
7) minimal time in the BK once chilled
8) yeast pitched during transfer from BK to fermenter.
9) cold fermentation (6C->9C>6C>3C)
10) same volume of stir-plate-propagated yeast from the same culture
11) grists and hops from the same lot of ingredients
12) MH and FWH
13) Spunding
Again, I wasn't interested to see if AA could mitigate HSO with hido brewing, but rather ask if AA is a direct substitute for SMB in a lodo process. In other words, are they equal in their effectiveness to scavenge oxygen and protect malt flavors, as well as what are the side effects downstream. I have the results of the brew days, as well as my own tasting notes. I will continue to take tasting notes along the way. A handful of folks I know whom are excellent performers in triangle tests will be given a repeated series of randomized tests once both beers are finished.
The Helles:
OG: 11.4 P
FG: 2.7 P
IBU: 15
EBC: 7
77% Best Pilsner
15% Best Vienna
5% Best Light Munich
3% Sauermalt
6 IBU Mittelfruh @ MH
6 IBU Perle @ FWH
3 IBU Mittlefruh @ SBH (15 min)
RO Water
3:1 Calcium chloride to calcium sulphate @ 50ppm Ca2+
AA - 75 mg/l in strike water, 10 mg/l in sparge water
SMB - 75 mg/l in strike water, 10 mg/l in sparge water
What intrigues me most about AA is that malt has a natural enzymatic system, ascorbic acid oxidase (AAO) and ascorbate peroxidase (AP) for utilizing AA to scavenge oxygen.
- AAO Abstract.png (56.92 KiB) Viewed 9824 times
It would seem illogical to fail to take advantage of this built-in system, unless there were some negative side effects. In fact, there can be negative sides effects to using AA, mainly that the oxidized form of AA, dehydroascorbic acid (DHA), can in turn become an oxidizer itself. However, DHA generally has a very short half-life, and yeast also have the ability to convert DHA back to AA and use it for their own cellular metabolism. In theory, as long as you use AA upstream of fermentation, then the yeast should ensure that there are no AA or DHA remaining to negatively affect the finished beer. Studies have shown that AA is effective at preventing thiol, phenol and polyphenol oxidation during the mash. This is consistent with Tech's theory on phenols and their flavor contributions. Kunze speaks about the importance of specifically not oxidizing polyphenols during the mash and boil as well.
- Reduced Thiols and Phenols.png (47.47 KiB) Viewed 9824 times
As a side note, citric acid (CA) is the most commonly used acid in lowering pH in sour beer production, and has its own antioxidant properties. Ironically, only one oxygen atom distinguishes citric acid from ascorbic acid. Both are readily available in fresh fruits to preserve and protect against oxygen degradation, and they are both likely present in sauergut. I need to investigate the composition of sauergut a little more, but based on the stability of the pH, redox potential and suite of microbes producing organic acids, it is very likely rich with oxygen scavenging organic acids. This blend of oxygen scavenging organic acids likely plays a significant role in sauerguts effectiveness in brewing, especially in combating HSO in the mash and boil.
I wanted to see if AA would be a direct substitute for SMB. I brewed up a third batch of helles (after the SMB and BB batches) to see if AA is a direct replacement for SMB. All other lodo practices were implemented, and the only variable was the the reagent. Both batches were brewed using:
1) pre-boiled strike and sparge water
2) underlet pumping for dough-in and subsequent transfer to BK
3) mash cap
4) copperless system
5) low boil (210-211F at the surface temp)
6) fast wort chilling
7) minimal time in the BK once chilled
8) yeast pitched during transfer from BK to fermenter.
9) cold fermentation (6C->9C>6C>3C)
10) same volume of stir-plate-propagated yeast from the same culture
11) grists and hops from the same lot of ingredients
12) MH and FWH
13) Spunding
Again, I wasn't interested to see if AA could mitigate HSO with hido brewing, but rather ask if AA is a direct substitute for SMB in a lodo process. In other words, are they equal in their effectiveness to scavenge oxygen and protect malt flavors, as well as what are the side effects downstream. I have the results of the brew days, as well as my own tasting notes. I will continue to take tasting notes along the way. A handful of folks I know whom are excellent performers in triangle tests will be given a repeated series of randomized tests once both beers are finished.
The Helles:
OG: 11.4 P
FG: 2.7 P
IBU: 15
EBC: 7
77% Best Pilsner
15% Best Vienna
5% Best Light Munich
3% Sauermalt
6 IBU Mittelfruh @ MH
6 IBU Perle @ FWH
3 IBU Mittlefruh @ SBH (15 min)
RO Water
3:1 Calcium chloride to calcium sulphate @ 50ppm Ca2+
AA - 75 mg/l in strike water, 10 mg/l in sparge water
SMB - 75 mg/l in strike water, 10 mg/l in sparge water