German Brewing

Good point. Best Malz have excellent caramalts. Many of them can be used up to 50% of the bill.

I'm using malts from Castle, except for the Caramunich which is from Weyermann. I feel that the belgians are less roasty/toasty than the Best/Weyermanns.

I did pitch my "normal" amount, which is underpitch comparing to the 0.75 / ml /plato rule. Maybe that's where it got wrong with my 10% caramalt. But I also feel that the belgian caramalt is harder to attenuate than the german.

I'm having some big issues with stability.

If the beer sits long in the bottle (or even in the fermentor) it gets tarty.

Like it's a different beer comparing to when it's "good". It tarts up, and gets dryer, but no off-flavors as such. Mouthfeel is also different due to the perception of it getting drier.

It sounds like an infection really.. but it does not get sour, or more tart over time, than how it ends up.

If feel it's also linked to the amount of speise. Those with more speise takes longer to tart up. And the process accellerates when the bottle is set cold for an extended time, so the opposite of how an infection would progress.

It somehow seems like the yeast is dropping out, leaving behind a tarty body.

The things I'm trying to look into is:

Does headspace in bottle matter? oxygen?
Maybe I overcarb them?

I never had an issue this markedly different when it came to keg or bottle conditioning. Although I never force carbonated my wheat beers.

One thing to consider is that maybe the recipe needs further adjustment, especially when---after a full conditioning period (which you seem to have had)---the final taste is lacking.

What is worth remembering is that one should really introduce fresh yeast at this stage, and ensure to crash out the old one. At Schneider, wheat beer remains at 1.0 - 0.0 Celsius for a few weeks before it is bottled.

Best