Hops and a range of hop products can be used to bitter cask conditioned beers and it is often the practice to dry hop them.
Beer bitterness is largely derived from the hop alpha acids and variety is of very little importance with regard to the quality of the bitter taste. In breweries with hop backs it may not be possible to use hops with high alpha acid content because they give insufficient depth of spent hops on the base plate to retain the hot break.
The variety of hops can have a marked effect on the intensity and quality of the hop character of beer. Liquid carbon dioxide extracts, which contain high levels of hop oils, show good storage characteristics and provide a convenient way of introducing hop character.
Range of Values
The overall range of bitterness is 22 – 35 B.U. For a particular brand the tolerance is ±2 B.U. of the specified level.
Although the overall range for dry-hopping is 9 – 140 gm per hectolitre(0·5 – 8·0 oz per barrel -0·2 – 5·0 mgs/ltr of hop oil) the usual levels are 9 -35 gms per Hectolitre (0·5 – 2·0 oz per barrel).
Dry hop flavour reaches a maximum after the hops have been in contact with the beer for 21 days.
Dry hops or special hop products should be added according to their contents of essential oils which may alter during storage.
It is often convenient to add dry hops or hop products at racking or when beer is fined.
Casks should be rolled after addition of dry hops or special hop products to ensure adequate mixing.
Dry hops should be stored in the cold, 2° – 4°C (36° – 39°F), prior to use.
There are several methods to measure the extent of evaporation which include:
The alpha-acid content of the hops at harvest should be available for all growths of hops and used when fixing or adjusting hop rates.
Reliable values should be available for levels of essential oils present in dry hops and special hop products.