Here's the passage:
Strong beers.— Until few years ago strong beers fell into two distinct classes — either very sweet and only partly fermented because the yeast had come out too soon, or overdry because they had been fermented completely by the traditional rolling in cask over several months. The latter method was that used at my brewery for producing Stingo — a method which took nine months. Needless to say, the losses of this very expensive beer were extremely high. In contrast, we found we could produce Stingo by continuous fermentation in two days instead of nine months without direct loss of beer or loss through development of acidity—either of the lactic or acetic variety. In addition, the beer could be produced with an intermediate degree of sweetness exactly as required.
Journal of the Institute of Brewing, Vol. 76, 1970, page 175.
Those two classes of strong beers are presumably ones which did or didn't undergo a secondary fermentation. And, with such beers becoming "overdry", it's clear that Brettanomycers was at work. Which is clearly what was happening with Stingo, being rolled around in casks for nine months. During which time it hopefully wouldn't turn into vinegar and need to be discarded.
I wonder what happened to Stingo when the continuous fermenters were removed in the late 1970s? I'm pretty sure they wouldn't have reverted to rolling it around in casks for months. They might well have just quietly discontinued the beer.
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Doesn't this contradict what people say elsewhere about continuous fermentation being suitable for high volumes of the same beer – i.e. your biggest sellers, not a minor speciality product? Did they run the CF plant long enough to make a year's supply of Stingo at once?
I struggle to understand what Bishop is saying here. I assume that the 9 month rolling around in a cask formed some function, otherwise why would it have been done. As you say, Ron, probably a bret ageing process. But he then says that continuous fermentation could produce a beer in 2 days with the 'sweetness required'. But they could have done that in a traditional open or even more modern conical FV - ok, not in two days, but certainly not nine months - he even alludes to this with his two types of strong ale comment? He seems to be comparing two different things. So, how did they produce a beer that emulated the traditional Stingo using CF?
Perhaps the CF process prevented the yeast giving up the ghost so soon, so it would attenuate more fully and you got a drier beer, without the risk and time involved in ageing it in casks.
I don’t know when Stingo was discontinued, but it was certainly available into the 1980s: it was listed as one of Watney’s products (with an OG of 1076) in Brian Glover’s “CAMRA Dictionary of Beer” (published in 1985).
John,
I think what he's saying is that in a traditional open fermenter they couldn't get the attenuation low enough and needed a long secondary fermentation to eat up the difficult to ferment sugars. It seems that in a continuous fermentation system the same attenuation could be achieved in primary.
Obviously, the version of Stingo from a continuous fermentation would have tasted very different to the oak cask version.
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