Gas purging the bottle with pressure filler gun...Why?

[trustyrusty]

Hi I am trying to get my head around the gas purging when filling a bottle. I totally understand you don't want oxygen in or as little as you can. If you use a carbonation cap, that is different and will be 100%. I watched a guy in a video - Gas purged the bottle, then filled it up to overflow, pulled out the filler and then left a gap of 2cm, then capped. Surely as you will the bottle everything including oxygen or co2 you put in is being pushed out, and then when you pull the gun out it leaves a gap filled with oxygen. Seems pointless? What have a missed? If I was going to put in the fridge to drink would I have to worry about gas purging anyway?

I can understand if you were going to store the bottles for a while, but I cannot see how the top does not get filled with oxygen unless you were in an air tight CO2 chamber?

 

[Blind Dog]

CO2 is heavier than oxygen so the idea is that the purging with CO2 pushes out the oxygen in the bottle, the liquid then pushes out the CO2. It reduces the chances of oxygenating the beer as the bottle is filled as there's little oxygen remaining in the bottle. As the bottle is full when you pull out the gun, the gap left behind will be filled with air, which is mainly nitrogen.

It's not a big issue if you're going to be drinking the beer fairly quickly, but it's worth doing if you're going to age the beer. Oxygen scavenging caps can also be used if it's a concern.

 

[mofox1]

Oxygen will mix into the beer while filling if you don't purge. Not a drama if it is going to be consumed very soon, but will cause storage issues otherwise.

I use a carb cap (with a bit of beer line on the end), but I don't leave them on the bottle - I'm usually filling a few at a time and just move the cap from one to another. I'll give the bottle a slight squeeze to remove the remaining headspace when capping with the normal lids to eliminate the O2 presence.

Edit: D'oh - ^Wot he said. I types too slow

 

[wynnum1]

Have been thinking about this and would think that if the bottles where filled with water and the water poured out in a CO2 filled chamber that would be the best possible. The chamber could also start out full of water and use the CO2 to replace the water.

 

[mofox1]

Have been thinking about this and would think that if the bottles where filled with water and the water poured out in a CO2 filled chamber that would be the best possible. The chamber could also start out full of water and use the CO2 to replace the water.

Great minds think alike... (?) Tried this a while ago.

Carb cap method:
- Filled bottle with water & attach carb cap
- pushed water out with CO2 (upside down over a bucket, water goes everywhere, meanwhile getting tangled in beer/gas line)
- fill with beer
- take cap off to replace with normal PET bottle cap
- give bottle a squeeze to push out recently introduced O2
- wonder why I went to the bother of the water in the first place
- skip water part for remaining bottles

 

[klangers]

Commercial beer fillers rarely purge with CO2.

Instead, they fill and then cause the beer to foam deliberately (there are several methods for this). The foam is, in effect, entrapped CO2. The foam rises up and overflows slightly, effectively purging the headspace of any air.

There should be no need to go to extreme lengths to pre-purge bottles. If you are getting that much oxygen pickup I would look at other parts of your process - especially if you are bottling into PET!

The main thing is to fill from the bottom up to avoid turbulence and splashing.

 

[trustyrusty]

the gap left behind will be filled with air, which is mainly nitrogen.

Thanks Blind Dog - FYI - wikipedia
"By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases"
I did not think N was that much .... thanks

 

[trustyrusty]

The main thing is to fill from the bottom up to avoid turbulence and splashing.

That is the most important I think.... works well ...cheers