Dissolved Oxygen Meter

[BrewHound]

To clarify -- I simply inserted the barbed brass nozzle on the O2 regulator into the opening on the bucket lid (i.e. in the middle of the rubber grommet). I kept a finger near the opening and could feel air leaving the headspace. After counting to 5, I pulled out the brass nozzle and turned off the regulator. Since I was too lazy to get out my oxygen stone, my goal was to try the simplest possible means of oxygenation first, before doing something more complicated.

After filling the headspace with O2, I put my finger over the grommet/hole and shook the bucket for a few seconds. Next, I popped open the lid, sanitized the DO meter, and took a reading.

One thing to note is that I have no idea if the oxygen was uniformly distributed, since I just measured the wort near the top of the bucket. I presume the shaking mixed it up pretty well. Also, whatever I did seemed to work, since I had a very active fermentation this morning, even though I set the fermentation chamber at 62F.

Thanks Lee, sometimes my interpretation isn't too good, and with the lid on I would say that would make it a fairly sound testing practice as all of the O2 will remain in the vessel.

Hope once I get my new system built (planning on putting in line oxygenation in) that I could borrow you and your meter for an afternoon to dial in the numbers on the system.

[DrPaulsen]

I won't be able to host until the spring.

Why don't we make this the January Tech Meeting?

Have Meter - Will Travel.

[BrewHound]

My personal opinion is that we should wait until the spring and take the time to gather some solid trial evidence and information to present.

That way data could be presented on a host of different sources.

[DrPaulsen]

Perhaps we could actually do some of the experiments for a tech meeting. We could bring over burners/kettles/chillers/fermenters and do a lot of the work in parallel. Just a suggestion -- it's not my garage.

CJ -- per Tom's note, the Tech Meeting would not be a presentation on the effectiveness of various aeration methods, but a collaborative effort to gather experimental data with parallel setups. We can always hold a follow-up meeting to present the results of the experiments to anyone that can't attend the first meeting.

I really like this approach for the following reasons:

• 1 Having additional folks on hand to observe the experiments should improve quality control.
  2. In this case, more "cooks in the kitchen" is likely to see us come up with some better ideas than I will in isolation.
  3. There is an improved pedagogic element -- more folks will learn by doing the experiments than by reading my slides & listening to me drone on.
  4. If the group has to wait for me to run enough experiments to have a meaningful, presentable collection of data, it could be a long wait.

[carrisr]

OK, assuming we want to do this for the January Tech Meeting, we need the following:

1. Host/location, date, time.
2. The plan. (Lee can you put this together?)
3. List of what equipment or supplies we need. Will result from item #2.

[carrisr]

Lee, do you expect that the type of container used (size, shape, head space) will make a big difference in the testing? If so we should try to have both 6 gallon carboys and buckets. I can bring up to 4 of my 3 gallon better bottles.

As for how we do the testing, I suggest we mainly focus on using pure O2 and try to come up with a repeatable "suggested method" that we can all put into practice.

There's already tons of data out there saying that just about any method using air (shaking, air stones, pouring between buckets) reaches a max level of 8ppm in a pretty short amount of time. I personally want to know the best method to get to various levels above that for higher gravity ales and especially for lagers.

Just my opinion of course, if others want to do test with air that's fine too.

[DrPaulsen]

Pragmatically speaking, I think we should use whatever vessels folks are using. I suspect the vessel type/shape does not matter as much as making sure it is relatively well sealed so the O2 doesn't splash out. If you're using air, I'm not sure that it would matter. I'm also not sure that the volume of the container matters that much as all this should scale pretty linearly. Putting a gas in solution with these techniques shouldn't be much different from putting DME into solution, aside from the inverted temperature-solubility relationship. If we were letting oxygen naturally diffuse from the air, I suspect things like the volume-to-surface-area ratio would matter, but probably not here.

Here are some techniques, just off the top of my head, but you guys need to provide feedback. The goal is to develop some confidence levels for various aeration methods that folks either are using or can be easily used. If you have a particular technique that you want tested, speak up. After we have a list assembled, we can rank them and plan to do the top 3 or 4.

Techniques
-Splashing to fill (vs height)
-Splashing to fill with an O2-flooded container
-Shaking with air (vs time)
-Shaking with O2 in the headspace (vs O2 dispensed time)
-Mix-Stir with air (vs time)
-Mix-Stir with O2 (vs O2 dispensed time)
-Aquarium Pump with diffusion stone (vs time)
-O2 bottle with SS diffusion stone (vs time) - wide open vs barely bubbling
-Aquarium Pump with O2-flooded headspace (i.e. flooding the headspace with O2, but using the aquarium pump to effectively stir the wort)

We're going to have to make the assumption that dissolving oxygen in chilled water is about the same as in wort. Also, I doubt we'll be able to repeat too many of the experiments on this scale, so we'll have to figure out a way to drive down the uncertainty. Maybe repeating one of the more popular techniques multiple times on a 1 gallon scale would work, but I'm open to ideas.

It will be imperative that we measure the DO at relatively closed to 70F, as the meter does not have ATC and I doubt the extrapolated spreadsheets work at nearly boiling temps.

Equipment I can bring:
1. DO meter
2. Mix Stir
3. Aquarium Pump
4. O2 Regulator & oxygen bottle
5. 0.5 um diffusion stone
6. Counter flow chiller

[DrPaulsen]

Having used the DO meter with the "add O2 and shake" method 7 times now, it seemed like a good time to post some new data. The technique I've settled on is to purge the bucket's headspace with O2 for a 5 count then put my thumb over the grommet, shake for a 10-15 count, and repeat. For each batch/iteration I've recorded, I have posted the starting gravity (OG), initial dissolved oxygen (DO_I), the number of times I repeated the "purge and shake" process (N), and the final dissolved oxygen (DO_F). The dissolved oxygen levels given are in ppm. I have not compensated for temperature in the measurements, but all of the worts were within 15F of each other, so the temp compensation errors should be small. Also, I did an open-air cal check on the meter before I started each iteration. The cal has been consistent to within +/- 0.1 ppm.

OG - DO_I - N - DO_F
1. 1.067 - 2.3 - 3 - 10.6
2. 1.052 - 3.0 - 3 - 13.0
3. 1.070 - 1.5 - 4 - 14.8
4. 1.034 - 1.5 - 3 - 11.5
5. 1.034 - 1.5 - 3 - 12.5
6. 1.053 - 1.5 - 2 - 13.0
7. 1.057 - 1.4 - 3 - 13.8

Regarding sample #3 requiring 4 iterations, please note that I ended up with more wort than in the other batches and the headspace was reduced. In all the other batches, I had about 1 gallon of headspace, but on batch #3, it was probably closer to 1/2 gallon. I checked the DO levels between each "purge and shake", but did not record those levels. It seemed to increase by increments of about 3 ppm, but I can't guarantee that since I did not record the data.

I brewed sample #6 yesterday and am not sure why it only took 2 "purge and shake" cycles. If I had to guess, I'd say I was distracted and either purged for a very long 5 count and/or shook for a longer duration. This might mean one could get by with less O2 simply by shaking for longer.

I think the data speaks to the fact that simply doing nothing to the wort will result in very low DO levels (8-12 ppm is recommended as a rule of thumb), while only a minimal amount of oxygen is required to reach recommended levels. The amount of variation in the DO_F is probably due to the lack of process control with my techniques, but since I'm just shooting for a range of about 12-14 ppm it seems to be working.

[JimPotts]

Thanks for the investigation.  This is some great data!

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[DrPaulsen]

I double-checked my notes. Apparently I'm too stupid to read my own handwriting sometimes. Batch #3, a Bock, only required 3 iterations of the "purge and shake" method. I'm not sure where the number 4 came from. My notes do indicate that there was a smaller headspace on that batch than the others and I tried to compensate by doing an 8 count of O2 before shaking. The updated list is as follows.

OG - DO_I - N - DO_F
1. 1.067 - 2.3 - 3 - 10.6
2. 1.052 - 3.0 - 3 - 13.0
3. 1.070 - 1.5 - 3 - 14.8
4. 1.034 - 1.5 - 3 - 11.5
5. 1.034 - 1.5 - 3 - 12.5
6. 1.053 - 1.5 - 2 - 13.0
7. 1.057 - 1.4 - 3 - 13.8

[Matt F]

Good info. My oxygen tank was empty the last couple times I brewed. They were not big starting gravities so I just shook the heck out of them. Lag times were much longer than when hit them with oxygen and an aeration stone for a minute or two. Bought new oxygen for my last brew which was a 1.079 OG and it was raging in just a few hours.

[-MG-]

Very interesting.

I have for awhile now used an agitating rod attached to a hand drill and create a funnel in my fermentor that allows oxygen in. I would be curious how this differs in oxygen levels versus just shaking it.

I've never experienced a stuck fermentation or poor attenuation from this method on all sorts types of beers.

[DrPaulsen]

I tried aerating with a Mix Stir wand today. After about 90 seconds of vigorous agitation, the DO levels had only increased by 3 ppm. Since the baseline DO levels of all my beers have been about 1.5 ppm, this should result in a starting DO level of 4-5 ppm. I haven't tested just shaking wort for 90 seconds, but it would not surprise me if it produced a similar DO level.

Given the poor performance of the Mix Stir, relative to the iterative "O2 & Shake" method, I don't think I'll be running any more experiments with it. Up next, I'll start running some experiments with an aeration stone and O2.

I've run 10 batches with the "O2 & Shake", where I flood the fermentor headspace for 5 sec with O2, then shaking it for 30 sec. Very consistently, this method has produced around 12 ppm of DO with 3 iterations.

[jjbuck]

I recall reading of fish kills in Macleoud(sp) Run.(the metro trout stream parallel to CP road) Seems that rain runoff from asphalt parking lots raised the temp of the stream enough to lower DO to a lethal level. I guess my point is that lower pitching temps would help raise DO but would also contribute to increased lag time.

[Matt F]

Yup, big rain=warm run off in to trout stream=less O2 in water=fish dead. If the run off to the creek were under control, the fish population could become more self supporting. Fun place I like to fish sometimes over my lunch break. There are some nice sized trout in there.