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02-02-2016, 07:55
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Contrary to my expectations, it seems that there is at least one fan of crap like this. That’s all the encouragement I need.

Once conditioning in the tank was complete, it was vital to keep air away from the beer. For several reasons:

“It should be emphasized that from this time onwards it is essential to protect the beer from absorption of oxygen. At the end of the conditioning period the action of the yeast will have reduced the pH to a low value of about 10. During subsequent handling and bottling there will inevitably be some rise in this value to perhaps 16-17. This high pH is of importance from the point of view of both biological and non-biological haze. Yeasts, notably wild yeast species, can grow at this pH; at pH15 their growth is slow and at below about 12 their growth will be completely inhibited. Oxidation of proteins is a frequent cause of haze in bottled beer and from this point of view also the lower the pH the less chance of haze. While danger of biological haze can be removed by pasteurization this process may accelerate the onset of non-biological haze, so that from all points of view the importance of the minimum contact with air cannot be over emphasized. In judging the susceptibility of a beer to these troubles which follow upon its absorption of oxygen the pH alone is not a complete guide. Of equal or perhaps greater importance is the actual amount of oxidation which has taken place as indicated by the 'poising' of the beer towards influences which can change its pH. As a parallel to this we may point out the difference in response to traces of acid and alkali of a non-buffered solution as compared with a buffered solution. As pointed out in Chapter 3 a single drop of a decinormal acid may suffice to swing the pH of a non-buffered liquid, such as distilled water or a solution of sodium chloride, through several units, say from pH 7.0 to pH 4.0; whereas the same amount of acid added to a buffer solution would have hardly any perceptible effect.”
"Brewing Theory and Practice" by E. J. Jeffery, 1956, page 337.
I’m not going to lie to you. I understood bugger all of that. Other than that contact with air was likely to cause haze at a later stage. And that was the last thing a brewer wanted. The whole point of the conditioning process was to create a beer totally free of haze or sediment. Unlike your modern hipster brewer, who’s trying to get as much shit as possible into the finished beer, so it looks “natural”.

I’m starting to wish I’d done A level chemistry. I really don’t get that stuff about buffered and non-buffered solutions and decinormal acid. It’s left me feeling a bit thick.

“In a similar way we have to distinguish between a beer which while having a high pH may have little poising action and one which has been oxidized sufficiently to resist subsequent agents which might reduce its pH to a safe value. If a beer has only been in contact with air for a comparatively short time its pH may have risen, but its 'poising’ effect may be small. In such a case the slightest growth of yeast may be sufficient to reduce its pH to a low value, so that the growth of the organism is rapidly inhibited before it has developed sufficiently to cause appreciable trouble. If, on the other hand, the beer had been exposed to air for a long time the consequent production of oxidized products would have supplied a reservoir of combined oxygen, which would prevent the pH falling and allow considerable growth of the organisms. Somewhat similar conclusions apply to the formation of non-biological haze. The actual amount of oxidation haze will depend upon the reserves of oxidized materials in the beer. From this point of view darker beers are less susceptible to the action of oxygen. Due to the presence of the substances called melanoidins to which reference has been made in an earlier chapter, such beers have a reserve of reductants which can minimise the raising of pH of the beer by contact with air or can counteract its influence.”
"Brewing Theory and Practice" by E. J. Jeffery, 1956, pages 337 - 338.

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In case you’d forgotten, we’re talking about conditioned beer being kept in cold storage tanks. About all I got from that is that darker beers are less susceptible to haze caused by oxidation. I’d never heard of that property of melanoidins before. Would beers coloured purely by sugar have melanoidins, or are they only derived from dark malts? A fair enough question, given many dark beers of the period contained nothing darker than crystal malt, and sometimes not even that.

This is probably the post I’ve least understood in the history of my blog. It does get a little better:

“It is from this point of view that the Indicator Time Test is useful. It measures the reserve of oxidation or reduction products in the beer. It depends upon the slow reduction of an indicator, the speed of the reduction being a measure of the reserve of reductants in the beer. An I.T.T. result of as little as 100 seconds can be given by a beer which has been handled in such a way as to minimize contact with air, whereas a beer which has been allowed to be in prolonged contact with air may take more than 1,000 seconds in the test. This brings us to the question of the use of air for blowing beer into the cold tank. Unless the brewery is collecting its own carbon dioxide the use of this gas for blowing the beer from one tank to another is uneconomic, and providing the beer is blown through carefully and is not allowed to be in contact with the air for too long the amount of air absorbed is usually insufficient to make a serious alteration in the beer. It is an advantage however for the empty tank to be filled with carbon dioxide before filling with beer. In some bottling stores the arrangement of compressors is such that C02 used for transferring the beer or for filling the tank can be returned to a storage vessel and thus used repeatedly, precaution being taken to avoid introducing air into it.”
"Brewing Theory and Practice" by E. J. Jeffery, 1956, pages 337 - 338.
Collecting CO2 would have been tricky for most British breweries as they almost all had open fermenters at this point. So my guess is that not many did. Meaning many probably did use air to move beer about. It’s another area where the UK lagged behind the rest of the world. American brewers had been using CO2 this way since the late 19th century. While German breweries had to collect CO2 if they wanted to carbonate because the Reinheitsgebot only allowed to use CO2 produced during fermentation.

Talking of which, carbonating the beer is next.

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