Capping on foam

Not sure what you mean about "does this make a difference for he carbing stage" question. Capping on foam refers to bottling beer that has already been carbonated. When you do this, there will be space between the beer and the top of the bottle, fillerd (temporarily) with foam. The reason for capping on foam is to displace air to keep some of the oxygen out of the bottle.

You can't really cap on foam with beer that hasn't been carbonated. Well, you could, but the amount of agitation needed to produce the foam in a pre-carbonated beer would introduce more O2 to the beer.

 

In addition, it isn’t as essential to get the all of the oxygen out of the bottle when you are bottle conditioning. As the yeast eat the priming sugar, they will also scavenge some of the oxygen dissolved in the beer. The less oxygen the better, especially for hoppy beers, but you don’t need to go to extraordinary lengths to have homebrew that tastes great a few months post-bottling.

 

I cap on foam all the time. I bottle straight out of my fermenter (w/o transferring to a bottling bucket). I just bottle straight out of the spigot on my fermenter, and during the fill I will give a hard pour for 1-2 seconds to generate foam. I'm not always consistent on the fill level (most fills are good enough), but I always have a good layer of foam spilling out of the top of the bottle when I cap. It's hard to do if you use one of the plastic bottle-fillers (not enough agitation to generate foam).

 

You are oxidizing your beer by bottling this way, this is not a good technique and the quality and shelf life of your beer would be improved by not doing this.

 

But if you drink the beer fast enough, you'll never taste the oxidation.

 

Oxidation at this level only takes a few days to become apparent.

 

No, I'm not.

 

When you "give a hard pour for 1-2 seconds to generate foam" what you are doing is dissolving oxygen into the beer to generate that foam. The more violently you agitate your beer during filling, the more oxygen will be dissolved into the beer. Listen to HB42. He knows what he's doing.

 

Ever wonder why trout live in streams, but generally not in ponds?

 

When you leave 5-10 ml of head-space in your bottle, all you're doing is leaving air in the bottle, which will slowly work its way into the beer, perhaps after the yeast has consumed most of the priming sugar when it can still use oxygen. Please do me a favor and tell me how much O2 is being absorbed by the beer during the hard pour. Are you sure that the CO2 being released isn't just pushing air away from the beer? Do you have a kinetic model that describes how much O2 is absorbed by the beer during the 15 seconds it takes to fill a bottle? I strongly suspect it's less than the air left in the head-space of the bottle after the fill, if you don't cap on foam. Also, this oxygen is in the beer, and will be in contact with the yeast during the early stages of priming, where it will be consumed by the yeast.

 

First, do me a favor and tell me how much O2 is kept out of the head space by purposefully foaming it!

Look: mass transfer is a function of surface area. The more surface area, the more mass transfer.

When you stir/splash, you are creating more surface area, increasing the rate of O2 transfer to the beer.

Yes, you liberate CO2, as the mass transfer works in the opposite sense as well. But you also entrain more O2.

I suspect you are right; carbonation is O2 limiting at first; then sugar limiting. But you don't want any O2 in the beer when you fill, you will begin oxidative reactions that reduce shelf life. That is why every single professional brewery evacuates their bottles with CO2 prior to filling.

Head space is certainly an issue in homebrew. I suppose I can't say for certain whether you will have improved shelf life by purposefully foaming the beer to push O2 out of head space vs not foaming and having more O2 in the head space. All I can say is I won't bottle homebrewed IPAs anymore.

 

Please do me a favor and tell me why commercial breweries purge their bottles with CO2 before filling them.

It's your beer, do as you see fit.

 

Maybe in theory, but since FarmerTed's beers don't taste like cardboard (unless they do) in practice its a bit different.

 

Where did that "credibility" thread go? I have some updates.

 

If you've tasted a few homebrewer's beers then you know the probability that his beer tastes like cardboard is more likely than not.

 

Drink a beer fresh, and you won't taste oxidization. And use oxy-absorbing caps.

 

That's bullshit, this is not theory, this is well studied and documented fact, oxygen makes beer go stale very quickly. Have you ever had cask ale that was a day or two past its prime? You don't have to taste outright cardboard to be experiencing oxidation, low levels of oxidation may not yield full blown wet cardboard but will definitely render a beer past it's prime after only a few days. Do you drink wine at all? Ever open a bottle of wine, drink some, and then come back the next day and drink some more? The wine won't taste bad, but it will never the same as it did when you first opened the bottle, and it will go progressively down hill from there. That's the wine becoming stale from low levels of oxidation, and the same thing happens to beer.

 

Well yea oxygen makes beer go stale no one is debating this, but you were saying oxygen introduced in the bottle oxidizes the beer in a few days. Do you have some studies or documentation of this? The reason I ask is because the studies I've seen, which admittedly was several years ago, said oxidized beer becomes apparent in several weeks, not days. Show me I'm wrong and I'll concede the point.

If you bottle already oxidized beer then I can see it tasting off immediately, but otherwise drinking a beer fresh usually doesn't give it enough time to taste oxidized.