Thursday, 23 October 2014

Brewing in WW II (part four)

I'm skipping one bit about nitrogen in malt that made my head hurt when I read it. We'll move directly on to yeast problems. Though you'll see that there's still a connection with the nitrogen level in malt.

And remember, this the less head-melty part of the article:

"The nitrogen constituents which are precipitated on cooling go forward into the fermenting vessel, and although some of them and those precipitated in the copper which have not been completely removed in the hop back rise to the surface with the first dirty head, a proportion, however, drop through the wort and settle on the bottom of the fermenting vessel; and, as Bishop has demonstrated (ibid., 1938, 70), forms points of disengagement for the CO2, the bubbles of which become coated with yeast as it rises through the beer and by thus bringing it to the surface is liable to restrict the attenuation of the beer. Where there is an excess of this type of nitrogen compounds this effect will be enhanced. The ph value of the wort has a direct influence on the cold break of wort, and when this is not normal the precipitation in the cold is not complete and a type of nitrogen compound will remain in a state of fine dispersion in the wort. There are other nitrogen compounds which are not precipitated on cooling but tend to coagulate as the ph value is altered during the progress of fermentation, and all these are capable of being adsorbed on the surface of the yeast cells. This coating on the surface of the yeast restricts its power of assimilating the yeast feeding material in the wort and results in a deterioration in its health and vigour. This effect was especially noticeable during the past year, for although the malts contained a high percentage of permanently soluble nitrogen the greatest difficulty was experienced in producing healthy and vigorous yeast crops. This was one of the most serious difficulties with which the majority of brewers had to contend throughout the war years, but it was most pronounced during the years when the malts were high in nitrogen and poor in quality. Another effect of the coating of the yeast is to cause it to agglomerate or flocculate, and when this happens it is inclined to purge out of the beer at an early stage of the fermentation. leaving the attenuations high and causing the beer to rack very clean. Slow cask conditioning is the result, and where there is any infection with wild yeast this has an opportunity of developing and cask frets inevitably follow."
Journal of the Institute of Brewing Volume 52, Issue 3, May-June, 1946, page 120.

This is how excess nitrogen buggers up a fermentation. They mess up the cold break and leave crap in the wort. This nitrogen crap coats the yeast and either drags it up to the surface or prevents it working properly. So brewers couldn't get a decent crop of yeast from their fermentations.

Presumably because it racked so clean there was too little yeast from the secondary cask conditioning. I guess there was a lot of flat beer in pubs. What a shame the Whitbread Gravity Book inspectors weren't around.

More about yeast problems:

"Yeast weakness has been a constant source of trouble throughout the country, and caused the brewer the greatest anxiety. The average gravity of beers when war broke out was down to 1041°, but this figure varied considerably in individual breweries, and when it became subject to a reduction of 20 per cent, some of those whose original average gravity was low were faced with considerable difficulty, which was appreciably increased in those years when the malts were so poor in quality. While lack of attenuative power is often taken as a measure of yeast weakness, it is not always so, as a weak yeast will more often than not cause excessive attenuation. The appearance of the yeast cells under the microscope is the surest method for determining yeast weakness. Signs of elongation of the cells are the first indication, and the more numerous and pronounced these become the greater is the deterioration in health and vigour. This is readily confirmed by the appearance of the heads on the fermenting vessels. The first effect of a falling off in health and vigour is the development of a "yeast bite" in the beer, which becomes more pronounced as the deterioration becomes progressive. It has been noticeable in low gravity beers of an average gravity of 1030° and under, and he was afraid that there have been many beers brewed of even a lower gravity. In beers of higher gravity a weak yeast tends to produce an unpleasant unclean flavour, and when this becomes very pronounced it renders the beer almost undrinkable. That flavour also is associated with an unclean nose, which can be readily detected on the fermenting vessel, usually at about half gravity, and, in fact, can often be detected as soon as the fermenting room is entered."
Journal of the Institute of Brewing Volume 52, Issue 3, May-June, 1946, page 120.

Occasionally there are higher gravity brews in brewing logs during the war years where it specifically says they were to produce a good yeast crop. It might also explain the weird practice of some brewers like Truman and William Younger who in the years immediately after WW I fermented fairly strong worts then blended them to produce a weaker finished beer. Were they doing that for the sake of their yeast, making sure some of it was healthy?

I'm not sure I follow why a weak yeast would over-attenuate. Makes absolutely no sense to me on any level. An "unclean nose" sounds more like an infection than just crappy yeast. It doesn't sound as if the end result was much fun to drink. Presumably in the difficult war years, even almost undrinkable was better than no beer at all.

Now something about Californian barley and nitrogen:

"In discussing possible war-time problems he had suggested that the lack of Californian malt might prove a difficult one (ibid., 1940, 272), he stated then that "Practical experience had shown that the use of Californian malt improves the brilliance of beers and assists in obtaining polish in bottled beers. It is evident, therefore, that it must be effective in adjusting the balance of the nitrogen constituents in the wort and effecting a stable equilibrium." Various opinions were expressed on this point during the discussion, and the general opinion appeared to be at that time that no serious difficulties had been experienced by reducing the proportion of Californian malt or discontinuing its use altogether. This, however, was experience gained in 1940 with the well-made malts from the sound barleys of 1939. Later on, when the quality of the malts deteriorated, and especially during the two very bad years, there is no doubt that the usefulness of Californian malt would have been clearly demonstrated. There is no question that the maltsters would have welcomed a supply of Californian barley, especially in those years when the quantity of held-over barleys was small and the quality was poor, as it would have enabled them to hold off malting the new season's crop until it had recovered from its dormancy and satisfactory results could have been assured."
Journal of the Institute of Brewing Volume 52, Issue 3, May-June, 1946, pages 120 - 121.

So it wasn't just the nitrogen content of Californian barley that made it attractive but also the fact that it was ready to malt earlier than British barley. Which also gave the home-grown stuff time to get into shape before it was malted. How complex this is.

Next time we'll be looking at flaked grains.

No comments: