It seems to have been a deliberate attempt to produce a hop with better bittering and preservative characteristics than existing English varieties. Demand for a high-alpha hop was great since imports of US hops had dried up.
Various brewers conducted trials with OP21, including William Younger in Edinburgh. It was spotting it in one of their brewing records that got me on its trail.
Not every brewer was positive about the trials, where some of the English hops were replaced by OP21. A smaller quantity of OP21 being used than English hops they were substituting. That ones another reason they were keen to try out OP21 hops during the war: you needed fewer of them. Quite an incentive, when supply was so tight.
"Mr. A. Rolph Pope, of Eldridge, Pope & Co., Ltd., Dorchester, reported on 10th November, 1942, as follows:—
“Trials were made of 0P21 in four brews, two of them being bottling beers and two draught beers. The proportion of 0P21 used in each case was one-quarter of the hops used; the quantity of OP21 was two-thirds of the English hops replaced. The English commercial hops used in the controls in place of the OP21 were Famhams. The trials were carried out in March and May, 1942. In each case trials were made of the OP21 as a dry hopper, both alone and mixed with a Worcester. In the copper tests, in the beer with which we were chiefly concerned, the hop rate was 0.6 lb. per barrel. In the Dry Hop.Tests, 0.22 lb. per barrel were used when OP21 was used alone, and when mixed 0.11 lb. of OP21 and 0.16 lb. of Worcesters per barrel.
"The conclusion reached was that when used as a copper hop the OP21 gave an unusual and somewhat unpleasant flavour which was perhaps more noticeable in the filtered bottle beer than in the case of the draught beer. As a dry hopper the same flavour was apparent. When used alone it gave a peculiar bitterness different from the characteristic bitter of an English commercial hop and when used with a Worcester, this flavour was still sufficiently pronounced to mask the flavour of the Worcester.
No laboratory tests were made for stability but the practical trials showed no difference between the beers in which the OP21 hop was used and the controls. This applies both to its use as a copper hop and a dry hopper. It is to be noted that the quantity of OP21 used was only two-thirds of the English commercial hops replaced.
"The trials showed that this particular variety would be quite unsuitable for use in this brewery as a copper hop, and still less suitable as a dry hopper. It must, however, be borne in mind that, as we stated when the suggestion that we should make a trial of these new varieties was first made, previous experience has compelled us to abandon the use of American hops in this brewery owing to the coarse bitterness which is extracted. This may be due to some peculiarity of the water. It is possible that by adjusting the blend used we might have overcome the objectionable flavour, but the quantity we had was not sufficient for further trials. We should be very pleased to make trials of another new variety.""
Journal of the Institute of Brewing, Mar - April, 1944, page 85.
I thought the last Farnhams had been rooted up before WW II?
Mr. Pope clearly wasn't a fan of OP21's flavour, even when mixed with other hops. Could he be right that water chemistry was the problem? Fascinating that Eldridge Pope had the same problem with American hops.