Dissolved Oxygen in Wort

[arturo7]

Fact or Opinion?

>Dissolved oxygen content of 8-16 PPM is ideal for yeast.

>8 PPM can be acheived with shaking, splashing or forced aeration (aquarium pump with stone).

>8 PPM cannot be exceeded without the use of pure oxygen.


Also, has anyone used one these DO measuring kits?
http://www.coleparmer.com/catalog/product_view.asp?sku=5300300

x

 

[a10t2]

1. It's hard to define "ideal" but 8-12 ppm is pretty standard. I haven't seen reference to many breweries going higher than that. At least in principle, you could minimize ester production by pitching at a higher rate and aerating less.

2. At room temperature, true.

3. It depends on temperature. Saturation at room temp is ~8 ppm, but at lager pitching temps it's ~12 ppm.

 

[944play]

 

[ajdelange]

The amount of oxygen which is optimum for a given yeast strain depends on the strain. I do mostly lagers and usually run around 20 ppm.

The Cole Parmer kit uses the time honored Winkler method which is fine for water but I'd be concerned about use with wort. Note that I have never used Winkler's method.

My concern would be that you would have trouble detecting the end point in the titration. The test releases iodine into the sample in proportion to the amount of oxygen dissolved and one actually measures the amount of iodine produced by titration with thiosulfate. Starch is added which turns deep blue in the presence of iodine and it is the extinction of the blue color that you are looking for. I fear that wort color might mask that to some extent. Another concern would be that as we all strive to keep our wort in the reduced state there will be a fair quantity of reductones in it and those would beat the thiosulfate to the punch in reducing the iodine so that less thiosulfate would be needed and the reading would be low.

The best approach, of course, would be to check the Winkler method against a DO meter.

 

[arturo7]

Thank you for the responses.


a10t2, would this indicate that if I shake, splash, aerate (aq. pump) at lagering temps, I may be able to achieve the 12-14 PPM without O2?


944play, any idea under what conditions this data was collected? The graph doesn't give any parameters of the test water other than temperature. It indicates 4mg/L at 70 deg. Mg/L pretty much translates 1:1 with PPM, indicating 4PPM.


Thanks for the info aidelange, this rules out the Winkler method for me. Too bad, I could see a one time expense of $40 to do some testing. DO meters are 10 times that for the cheapies.

 

[lamarguy]

I've measured 72F 1.058 wort aerated with sterile compressed air after applying ~5PSI of top pressure for ~30 minutes. The meter read just below 11PPM.

Since that experiment, I've always used inline compressed air instead of oxygen for wort <= 1.070. However, I still use inline oxygen for wort higher than 1.070.

 

[arturo7]

A couple questions if I may, lamar...

What is your source for this compressed air?

Assuming you used a DO meter, where did you get it? Surely, you don't have these things laying around?

 

[lamarguy]

What is your source for this compressed air?

"This" compressed air comes from a twin-stack oil-less compressor. Sorry couldn't resist.

I use an inline desiccant filter and sterile filter. The sterile filter housing can withstand ~15PSI without rupturing but I normally apply ~8PSI when chilling or transferring.

20PSI is pushing it. Don't ask me how I know.

Assuming you used a DO meter, where did you get it? Surely, you don't have these things laying around?

Borrowed from work...

 

[arturo7]

I was hoping you were using a wicked DIY filtering system on a standard compressor...

 

[lamarguy]

I was hoping you were using a wicked DIY filtering system on a standard compressor...

Resurrecting this thread to post a link to an inexpensive oil-removal filter. It's 95% effective and able to handle 125psi.

If you're extra cautious, you could place two of them in series. They also make make one with a red dye to indicate when the filter needs to be replaced (saturated with oil).

This, combined with a lab quality hepa filter, would allow folks with oiled compressors to aerate wort using compressed air.

 

[jdieter]

Noticed the Pall filter is for fluids, how do you know you getting .2um absolute filtration with air? Air filter construction is significantly different than a fluid filter. The fluid becomes intrinsic to the filters particulate holding ability. Also where are the brew shops getting the small inline filters they sell, I've had no luck finding the manufacturer.

 

[lamarguy]

Noticed the Pall filter is for fluids

Correct, the Pall 50A is rated for fluids but that doesn't mean it's not effective with air. I'm sure it's slightly less effective but we only need 0.5 micron filtration to ensure sterile air. The 50A is rated for 0.2 micron liquid filtration.

I chose it over the Pall 50 (rated for air) because the 50A has a prefilter and should last much longer.

Both the 50A and 50 are rated for 60 PSI and are autoclavable. They are superior when compared to the filters sold by homebrew shops.

I just called the laboratory technical line at Pall, and the representative said the 50A isn't rated for air filtration but will provide 0.5 micron air filtration, at a minimum.

 

[jdieter]

Great to know Pall techs confirmation it will handle air to 0.5 mic. Where are you buying your Pall filter, do you have to buy them in box quantities? I like that it can be autoclaved. I try to keep LHBS filters clean but who knows how effective they are after repeated use.

 

[lamarguy]

Where are you buying your Pall filter, do you have to buy them in box quantities?

I purchased two on eBay for $16 + shipping.

Ya, otherwise, you'll have to drop $100+ on a box of 10...

 

[arturo7]

interesting, veeerrrrry interesting


thanks LG