German Brewing

So say you have done the whole low o2 process, mashing, spunding, everything. How long is the fresh character retained for you? How about keg conditioned as well?

This is a very, very, very complicated question.

The slightest bit of oxygen ingress post-ferment makes it disappear within days to weeks. We're talking in the parts per billion levels here. The commercial standard is under 0.1 ppm (100 ppb) oxygen at packaging. Oxygen ingress can come from sources as innocuous as the little pocket of air trapped between the keg post and your grey gas disconnect when attaching it to your keg. Or from impurities in your co2 source. Or from diffusion across your plastic tap and gas lines.

Additionally, if you get even the sightest bit of autolysis in your lagering keg because there was too much yeast carried over or it wasn't very healthy, the dead cells will release oxidizers which spoil the fresh flavor.

Flavor stability is the final frontier...

Right now my beers stay fresh for between 2 and 3 months after racking to the lager keg. Before I started spunding, the fresh flavor was gone in 3 or so weeks. My DO meter was telling me at the time that I picked up between 0.3 and 0.4 ppm when racking the fully fermented beer into a co2 purged keg.

Nowadays my approach is to carry as little yeast as possible into lager. I allow my primary to start building pressure during the tail end of the fermentation so that the beer is already carbonated before I rack to lager. I ferment at 9c until I have 1% extract left and then aggressively drop to 6c by 1 to 1.5c per day. This gets most of the yeast to drop out, and I can rack to the lagering keg with less than 0.5% extract remaining.

I think it's best to then leave the lager keg untapped for 3-4 weeks to clear up - I even stopped using my spunding valve during the lagering stage because there's so little extract carried over (I still use it to regulate pressure during primary).

I stopped using co2 to push beer too. I target a bit higher carbonation (3ish volumes) and just accept the fact that the beer loses carbonation as I get towards the end.

I think the keg should be consumed within a month of tapping it.

This is a frustrating hobby :/

After witnessing firsthand how unbelievably difficult it is to maintain the "fresh" flavor, I'm dumbfounded that I can walk down the street to any local dive bar, order a Bud heavy, and sure enough it's got the fresh flavor. Yet no "craft" beer I've ever tasted in my life has had the fresh flavor. The macros are the real pros. I just wish Budweiser would make a 5% abv, 18-20 IBU beer made with 80-85% pale malt, 15-20% Vienna, and a dash of crystal instead of using 30-40% rice. If they did that I might just quit homebrewing.

Nowadays I just have to shake my head whenever I hear craft beer snobs disrespecting macro beer. Ignorance is bliss, I guess.

But I also have to shake my head at the macros. Their processing is so tight that if they wanted to, they could make craft-style beer that absolutely blows the entire craft industry out of the water. But for some reason they just keep making low gravity rice beer.

Hence the love for the German macros around here. Good recipes made with high tech, modern processes.

It seems like to me when oxidation sets in with the use of lodo/smb the results are way more dramatic.

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I think you are starting to get autolysis at around the 2 month mark.

Even if there isn't a significant amount of autolysis happening - that is, it isn't causing any noticeable off-flavors per se - it only takes very low levels of autolysis to release oxidizers which will make the fresh flavor disappear.

It is difficult to achieve highly stable beer without doing what is generally done to achieve it, which is filtration and most likely pasteurisation. A good keg never lasts us that long, so I'm OK with the 2 month limit.

0.1 mg/l is the industry target. It used to be 9 months stability, but most German macros achieve 12. Thus said, although many aim for 0.1 mg/l they often get 0.3-0.4 -- which might imply that Umdruecken into a purged vessel in order to take it off (most) of the yeast is an option.

The only problem is that our meters don't have enough accuracy. The Extech is 0.5 mg/l accurate, and so is every other instrument in that range. For 0.1 mg/l accuracy one would have to spend at least two to three times more.

I've still had no time to do my Diatomaceous Earth filter tests. This process is completely under water, so it should be possible to achieve better results than with depth (e.g. plate) filters.

I had filtered lager stable for quite a while (3-4 months), but I certainly oxidised it a bit during the process. So it's a fickle statement.

The good news is that a DE filter for home use is not too difficult to build in principle. The hard bit will be to figure out how to purge it and ensure all air is really gone before anything goes. The bad news is that the low flow-rate from Cornelius kegs makes it completely unsuitable for DE filters. One really needs at least a 3/4" pipe/hose and a 350W pump.

I also have to wonder if it's not just the greater magnitude of flavor loss, but whether the staling compounds that arise in lodo beer are somehow different than those in hido beer.

Case in point, take the sickeningly sweet stale honey flavor in stale imported light lagers and the soy sauce/dog kibble flavors of stale dunkels and doppelbocks. I haven't experienced those in stale hido beer - they only seem to appear in beer that was originally brewed lodo, but then went stale due to heat + oxygen/radicals + time.

To link this all back to my theory on malt phenolics, HSA/HSO will cause many of these phenolics to polymerize into polyphenols in the mash. Some of these polyphenols may then actually precipitate out as break material during the boil e.g. upon finding some protein to bind to. But what happens if we keep these nice phenolics intact during the hot side, allow them to carry over into the finished beer, and only then expose them to oxygen/radicals + heat + time?