View Full Version : Help

02-12-2004, 12:44 AM
How do I get rid of DOs in beer?

dick murton
02-12-2004, 05:35 AM
The key is not to pick up oxygen after you have transferred the wort into the FV, apart from the initial wort oxygenation required for good fermentation by the yeast.

After the initial fermentation is complete - do not rouse with air to get the last couple of degrees of attenuation out. All this will do is create off flavours, particulalry diacetyl (butterscotch) and later in the process, once the beer is cooled, probable hazes and off flavours including the dreaded cardboardy flavour.

When transferring from one tank to another, ensure the transfer mains and hoses are purged out with water, ideally dearated water, to remove any pockets of air. This has to be done at a high flow rate, eg 70 hectolitres / hr through 40 mm ID pipe. Then chase the water out with the beer ensuring no air is trapped in the system between the water and the beer.

Ideally purge the receiving tank through the bottom inlet, with CO2 to form a CO2 blanket at the bottom (CO2 being heavier than air). Start the transfer flow rate off fairly slowly so you don't create a fountain in the receiving tank. Nitrogen can be used, but doesn't form a blanket at low level, so you have to purge for longer.

Purge out filters with water (again ideally with dearated water), and then blow out the water with CO2 or nitrogen before filling with beer to reduce dilution.

Ensure the CO2 or nitrogen is oxygen free. Often gasses supplied are not guaranteed oxygen free. It only takes a minute percentage to add oxygen to beer.

Use nitrogen or CO2 for top pressure gas, not air.

Oh, and finally, or actually firstly, the plant should be designed with conical bottomed tanks for quiet fills, and easy purging of lines, with no tee pieces or similar to trap gas (or infection)

If you have high oxygen in beer, you can carefully purge with oxygen free nitrogen or CO2 - but since this tends to cause haze problems, preventative action is best.


02-12-2004, 04:14 PM
Thanks Dick your real asset to the message board.
I have pretty much eliminated the problem to the bottle machine,
wounderd if anyone had a design for a basic DOs tester?

02-12-2004, 09:08 PM
Thanks to all those who have offered info to me, you have all helped greatly.
I have fixed the purge problem on the bottle machine; we put another rail to activate the snift valve so the co2 has longer to purge the air out of the bottle to atmosphere. I dont know how the other brewery that owned it before us coped with it?
Thank you

02-13-2004, 03:34 PM
Stevenson Reeves and Zahm & Nagel sells air testing devices which both works in a way that you can test a bottle or sample bottle by desolve co2 and air from the beer and let the gas go in to a chamber with caustic solution, co2 will react with the caustic and the headspace that will be left in the caustic chamber is air. This chamber is graduated in ml.