[Big Monk]

In reading about methods of preservation, shelf life and LODO, K-meta was mentioned for use in low 02.

I would remember a few things if you entertain its use post fermentation:

 - Sulfites will actively scavenge oxygen already dissolved into the beer as well as oxygen that WILL dissolve into the beer, but only to a certain point. For example, if we dose the finished beer with 10 ppm of Sulfites (we'll model K and Na), we get the following:

For both KMeta and NaMeta: 10 ppm of metabisulfite will scavenge 2 ppm of oxygen (5:1 reducing power)

For both KMeta and NaMeta: We observe a pH shift of 0.1 pH units per 100 ppm of metabisulfite. That equates to a 0.01 pH shift per 10 ppm of metabisulfite. I have no empirical basis for this post fermentation, however, so treat that as a general aside.

For KMeta: You should track the K and SO4 contributions. Assuming full usage (we'll talk about that in the next bullet) of all the available metabisulfite, we can expect 35 ppm of K per 100 ppm of KMeta and 86.4 ppm of SO4 per 100 ppm of KMeta. This translates to 3.5 ppm and 8.64 ppm of K and SO4 respectively.

For NaMeta: You should track the Na and SO4 contributions. Again, assuming full usage of all the available metabisulfite, we can expect 24 ppm of Na per 100 ppm of KMeta and 101 ppm of SO4 per 100 ppm of NaMeta. This translates to 2.4 ppm and 10.1 ppm of Na and SO4 respectively.

- In order to maximize margin and protection when adding post fermentation, you should ensure that your transfers between vessels (fermenter to keg and keg to keg) are closed transfers.

This is important because if you transfer oxygen along with the beer and then dose it with sulfites, you aren't getting any protection and are merely adding K, Na, and SO4 to the finished beer. For example:

If you have 0 ppm DO in your beer after fermentation, but then open transfer or do a subpar closed transfer, you have the potential to pick up oxygen on the way to the packaging vessel that will "eat" up your sulfite dose. Let's say you pick up 1 ppm of oxygen on the way to packaging. That means you effectively lose 50% of the scavenging power of the sulfites to oxygen pickup before you drink.

Hopefully this helps.

[curtdogg]

In reading about methods of preservation, shelf life and LODO, K-meta was mentioned for use in low 02.

I would remember a few things if you entertain its use post fermentation:

 - Sulfites will actively scavenge oxygen already dissolved into the beer as well as oxygen that WILL dissolve into the beer, but only to a certain point. For example, if we dose the finished beer with 10 ppm of Sulfites (we'll model K and Na), we get the following:

For both KMeta and NaMeta: 10 ppm of metabisulfite will scavenge 2 ppm of oxygen (5:1 reducing power)

For both KMeta and NaMeta: We observe a pH shift of 0.1 pH units per 100 ppm of metabisulfite. That equates to a 0.01 pH shift per 10 ppm of metabisulfite. I have no empirical basis for this post fermentation, however, so treat that as a general aside.

For KMeta: You should track the K and SO4 contributions. Assuming full usage (we'll talk about that in the next bullet) of all the available metabisulfite, we can expect 35 ppm of K per 100 ppm of KMeta and 86.4 ppm of SO4 per 100 ppm of KMeta. This translates to 3.5 ppm and 8.64 ppm of K and SO4 respectively.

For NaMeta: You should track the Na and SO4 contributions. Again, assuming full usage of all the available metabisulfite, we can expect 24 ppm of Na per 100 ppm of KMeta and 101 ppm of SO4 per 100 ppm of NaMeta. This translates to 2.4 ppm and 10.1 ppm of Na and SO4 respectively.

- In order to maximize margin and protection when adding post fermentation, you should ensure that your transfers between vessels (fermenter to keg and keg to keg) are closed transfers.

This is important because if you transfer oxygen along with the beer and then dose it with sulfites, you aren't getting any protection and are merely adding K, Na, and SO4 to the finished beer. For example:

If you have 0 ppm DO in your beer after fermentation, but then open transfer or do a subpar closed transfer, you have the potential to pick up oxygen on the way to the packaging vessel that will "eat" up your sulfite dose. Let's say you pick up 1 ppm of oxygen on the way to packaging. That means you effectively lose 50% of the scavenging power of the sulfites to oxygen pickup before you drink.

Hopefully this helps.

Thank you for all the great information and food for thought.
I am definately working on improving my processes. I only brew 5 gallons at a time, so I feel any addition of K, Na and S04 would most likely be negligible. 

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[Robert]

You could preboil and chill the water for the finings but any opening of the system would expose the beer to some oxygen, so perhaps a way through the in post with CO2 pressure could be used?

Yeah, my method is to remove the gas post, quickly inject the finings with a syringe,  replace the post, and do a number of purge cycles with the PRV.  I guess I'm down to DO in the solution.   Preboiling and cooling to 160°F works for gelatin, minimal pickup, but still some I suspect.  But I kind of prefer isinglass, which requires cold water and lots of time on the stir plate.  It's as well aerated as a stirred starter!  That's where I wonder if it's really significant. (120mL @ 8ppm (nominal) in 20L ==> close to bupkus? ) How do commercial brewers address this? I think freeze dried isinglass already contains some sulfite as preservative, so maybe a pinch more is compatible? I should probably RDWHAHB.