It's rare to find am old recipe using exclusively hops from the most recent season. Brewers had a good reason for using older hops - the size of the crop, and hence the price, varied greatly from year to year. In years when hops were cheap, brewers would buy more hops than they required. This gave them some insurance against years when the crop was poor.
We all know that hops deteriorate with age, so how could ones two, three old, or even more, be of any use? Brewers weren't daft. They realised that by storing their hops cold the deterioration could be significantly slowed down.
"The Cold Storage of Hops
F. Babak, of the United States Department of Agriculture, has made some long-term experiments on the storage of hops which are reported in the Brewers' Digest (Sept., 1943). Six samples of hops, four home grown and two imported were stored for 5.5 years in cold store and ordinary store. The cold store was kept at a temperature of 38° to 40° with about 47% humidity, the ordinary store under fluctuating conditions according to the season. Samples were taken at various periods from three months upwards and examined physically and the resins estimated. The object was to find the rate of deterioration and incidentally as to whether there was any variation in this respect as regards seeded and unseeded hops, some brewers being of opinion that the presence of seeds made a difference.
The author’s results bear out the experience of the merits of cold storage we have found in this country if allowance is made for the difference in the temperature of the “cold stores,” for here the temperature of a cold store is much nearer freezing point. The figures are interesting as showing the drop in alpha-resin and increase in beta-resin during the first 21 months in cold store, an important difference as regards preservative power although the total soft resins has decreased much less. In ordinary store the change over is far more marked in nine months, and in this respect the seeded hops show up much worse than the seedless ones, a difference that is not noticeable in cold store. There was also a difference in the time a cheesy odour developed ; it started in the seeded hops after nine months’ ordinary storage, but with seedless hops not until 15 months had elapsed. In cold store the cheesy odour did not occur until after 27 months."
The Brewing Trade Review, December 1943, pages 358 - 359.
I was surprised that the beta resins increased during the first 21 months of cold storage. Not heard about that before.It seems a bit odd. Nor that seeded hips deteriorated more quickly than seedless hops. That's quite important, as English hops always had seeds. While continental ones didn't.
It's s shame that the analyses of hops at different ages weren't included in this article. Anybody have the Brewers' Digest for September, 1943?