Britain's own native oak, while eminently suitable for barrels, had been used up long before WW II. If you've been paying attention to the discussion of the Burton brewers Baltic trade, you'll remember that it was often on a barter basis. In return for beer they took barrel staves. Memel oak it was usually called. Which, as the region in question has changed nationality a few times in the last couple of hundred years, is a more accurate designation than Poland or Russia. (I mentioned Memel to my son Andrew this morning while waiting for the bus. "That's the north of East Prussia isn't it?" Clever boy.)
In 1940, I can't imagine any oak was being shipped across the Baltic to Britain. It wasn't a new problem. The same difficulty arose during WW I. And during the Napoleonic Wars, in the period when Russia was allied with France.
One of the biggest problems facing brewers at the present time is that concerning cask timber. After Russian and Polish oak American oak is the material to which one's attention naturally turns in these times, and many brewers must be much concerned at the prospect of having to use a material so well known to communicate undesirable woody and other flavours to British ales, particularly those of pale ale type. English oak is stated to be devoid of these defects, but it is doubtful if sufficient of this material is likely to be available to alleviate the cask timber problem to any marked extent. It is to American oak, therefore, that one must look for relief, and the question immediately arises: How can this timber be treated in order to make it suitable for use with British top fermentation beers ?
It may as well be stated at once that there is no simple answer to this all-important question. The whole matter was gone into very thoroughly after the last war, and no very satisfactory conclusions were reached as to the cause and cure of the strong flavour communicated to beer by the use of casks of American oak. The problem turned out to be much more difficult and complex than was expected, so it is felt that a brief summary of the work carried out by Professors Groom and Schryoer may assist brewers to understand the nature of the problem.
The objectionable "woody" taint may be due to—
1. The use of the wrong species of oak ("American white oak" is a very broad term and many different species or types of oak may find inclusion in this collective name).
2. The felling of the right species of oak at the wrong season of the year.
3. The use of heartwood of an appropriate species which is either too old, or (what is more likely) too young.
The differences between the suitability of the various species included in the term "American white oak" for beer-cask making appear to be due, "not to any specific extractive which imparts a deleterious flavour to the beer, but rather to fundamental differences in the chemical and physical properties of the timbers themselves."
It was further found that the ability to impart the objectionable flavour was not produced by the method of cutting the staves, nor by the presence of sapwood, or by the presence of micro-organisms in the wood. The last point was gone into with special care, for the heartwood of which the staves were made was found to contain large quantities of starch, which might have been expected to promote growth of moulds and bacteria. This was a feasible hypothesis, particularly since micro-organisms of these types are capable of producing curious "mouldy" or "musty" odours and flavours, not greatly dissimilar from the "taint" of American oak. It was found, however, that this hypothesis was incorrect, the "taint" being inherent in the timber itself and not due to microbiological action.
"The Brewers' Journal 1940" page 496. (Published June 19th, 1940.)
I think it's pretty clear that beer was coming into direct contact with the wood of the barrel. Otherwise how could the oak "communicate undesirable woody and other flavours"? What I don't quite grasp is why this problem should be so particularly acute with British type top-fermenting beers. Unless, of course, it's just because everyone else did line their barrels.
How did they overcome these problems with American oak? You'll have to wait for part two of the article. Or rather for me to transcribe part two. It was published almost three-quarters of a century ago.