"Brewing Science & Practice" by H. Lloyd Hind is brilliant when it comes to hops. There's so much on the topic, I've only room for a small excerpt.
I should be enjoying my second day in the archives at the moment. Snapping Barcaly Perkins WW I brewing records or some other fun documents. I'm so excited. Give me another couple of years and I might get photos of every year of the Whitbread records. Wouldn't that be great? Well, maybe not for you, but it would for me.
Some typical central European varieties, such as Saaz and Hallertauer, turn up in British brewing logs. Barclay Perkins often used Saaz for dry hopping their more expensive beers and sometimes used Hallertau as a copper hop.
Occasionally, Polish or Yugoslavian hops were used, normally mixed with British varieties as copper hops.
North American hops
American hops had been used in Britain since the 19th century. Most came from the West Coast where large amounts had been planted after a form of mildew virtually wiped out New England hop gardens in 1910. The absence of the diseases to which hops are susceptible, particularly mildew, had been the driving force. However, by the 1930's this was no longer true.
The main West Coast hop-growing regions were Sonoma, Russian River and Sacramento in California; the Williamette Valley in Oregon; and the Yakima Valley in Washington State. The commonest variety was the Oregon, also known as Late Cluster. It was thought to be a cross between an English hop and wild American hops. It had a high lupulin content an excellent preservative qualities. The only drawback was the strong blackcurrant flavour that meant it could not be used on its own in British Ales.
In the brewing logs, American hops are very common and are referred to as Oregons, Pacifics or Californian. Usually they make up no more than one third of the copper hops. Often they were used when quite old. In 1918 and 1919 Whitbread used "Pacifics" from the 1911 and 1913 crops. Presumably their high levels of bitterness and good preservative powers made American hops good for keeping for long periods. "Pacific Coast hops can rarely be used immediately after arrival in England, unless the liqour is very gypseous. In the majority of cases they are to be preferred as yearlings [more than a year old], when they give a milder flavour with adequate preservative power."
Large amounts of hops were grown in British Columbia in Cananda, mostly in the Fraser River Valley and on the Sumas Prairie. The most important varieties were English Fuggle's and Goldings which had been planted in the the middle of the 19th century. These hops were generally similar in flavour to their English ancestors. Some American Cluster hops were also grown.
In Australia hops were grown in southern Tasmania and the Owens River Valley in Victoria. Neither area produced any great quantity of hops. Rather more were grown in New Zealand - 35,000 cwt in 1935 - and some of these were exported to Britain.
Use of hops
New season hops were not usually used until at least three months old. When new, they were too bitter. To achieve a constant level of bitterness in the finished beer, hops from the most recent season were blended with older hops in a gradually increasing proportion. In the brewing logs, it's very rare to see 100% hops from the most recent season. Usually a blend of at least two ages of hops was used.
A higher hopping rate was employed in the summer when the preservative power of the hops was more needed. Filtered beer also needed to be more heavily hopped. Even Pacific Coast hops were used for dry-hopping filtered beer in tanks.
A majority of brewers preferred Goldings for dry hopping, because of their delicate flavour. Good quality Fuggle's, though coarser in flavour, were also used, as were Continantal hops such as Saaz, Hallertau or Styrians. Barclay Perkins usually dry-hopped with Goldings, though they sometimes used Saaz or Styrians. Though they didn't dry hop all their beers. Their Pale Ales were all dry hopped, as were the strong K Ales (KK and KKKK). Their Mils, Porter and Stout had no dry hops.
Stronger flavoured hops were mostly used in the copper. "It is generally possible to use a stronger hop with mild ales and dark ales in which the hop rate is low, than in pale bitter beers for which a higher hop rate, combined with delicacy, are reequired. It is not generally possible to increase the hop rate with the stronger flavoured hops in order to increase the bitterness, as it usually gives rise to an objectionable rankness." It was possible to use more strong hops in beer brewed with water high in gypsum.
Resin content of hops
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