So just more theory then. And very controversial, too, in terms of mutation models. I’m not sure I’d want to offer that as any form of supporting evidence for mysterious claims made by breweries and their marketing department’s spiel, which likely has more to do with selling beer than genuinely fortuitous outcomes of unconsciously repitching slurry for decades.
Having slept on it, I can divide my skepticism here. There’s the logic among home brewers (once including myself) that pitching multiple yeast strains is going to add some desirable, unique complexity in the end product. Something demonstrably worth the extra effort. Something 'special'. As I already typed I no longer accept this to be true, based on my experience involving many trials. Biased by my own taste mainly, to be fair. But this isn’t necessarily the same as serially repitching a brewery culture over at least several decades. If the brewery's yeast went bad it was replaced by calling in a favour. No big deal really, the main focus was producing beer and selling it. I think that's the hard reality fogged in mysterious, romantic stories.
For those that have apparently remained good for long periods, how do we know the beers produced haven’t changed due to the yeast population evolving ‘this’ way and ‘that’ over time, becoming a mixed population? I’m not talking about abrupt changes, ‘good’ or ‘bad’. Gradual change. This is a more realistic model, which doesn’t require anything to hide behind. We both know what would likely happen if a pure brewer’s yeast colony were cultured up and serially repitched by the bucket load over years. It would diversify and become a mixed population. Genetic diversity accumulates over time. Not necessarily different strains mind. But that is possible and they’d be closely related and perhaps more compatible than a designed mixture of strains. We hear a lot of talk about multi-strain yeast cultures, but, again, there’s rarely any evidence to support the claims. What I’d like to see is some credible evidence to back up the claims. That’s not too much to ask for, is it? As a proud Brit who enjoys a good English pint, I’m more than happy to defend British brewing heritage, but I refuse to talk shite about it. How difficult can it be to design a project, perhaps for a PhD student at Herriot-Watt or Nottingham, to characterise a rumoured multi-strain brewery culture, described as ‘among the finest in the land’, then ferment with individual strains and various combinations of strains so as to demonstrate the brewery’s marketing department aren’t talking shite? If it's as good as they claim, isn't it worth preserving? The fact such evidence hasn’t been presented so far says something. The methodology (technology) to do so quite easily has been around for decades. I’m afraid it looks to me like they’re talking shite. And I get excellent results using pure yeast strains from traditional English breweries to ferment my home brew. I know they’re pure because I plated them out and isolated them myself.
Edit: Interim summary: the competing hypotheses here are: stable multi-strain brewery yeast vs evolving chancers flogging beer. It seems to make more sense when you ditch the romanticism.
