Non-isomerized Hop Products
The alpha acids are unchanged during processing non-isomerized products. As a result, the products can only be added to the kettle only during wort boiling. Products included in this group are listed below.
Hop plugs are used in the United Kingdom as a convenient means of dry hopping cask-conditioned ales and by brewers with traditional hop backs who cannot use powder pellets. The hop plug is technically a Type 100 pellet, and is made by compressing whole hops (unground) into a plug that measures between 10 and 30 mm in thickness, depending on the weight.
Hop pellets are nothing more than whole hops mechanically processed by removing foreign material, milling in a hammer mill, blending batches of hops together for product consistency, pelleting through a standardized pellet die, cooling, and packing in aluminum based foil packs.
Regular or Standard Hop Pellets (Type 90)
One of the most common hop pellet on the market is the regular or standard (Type 90) pellet, which are whole hops ground and pelletized.
Concentrated Hop Pellets (Type 45)
Another type of pellet on the market is the concentrated (Type 45) hop pellet, also called "enriched" pellets. This pellet is derived from a process in which the coarser "waste" fraction is mechanically separated from resins and oils at subfreezing temperatures (- 35°C).
Stabilized Hop Pellets
In stabilized pellets, magnesium oxide is mixed in with the hop powder and the mixture is then pelletized.
Hop extracts are made by passing a solvent through a packed column of milled hops to collect the resin components followed by the removal of the solvent to yield a whole or "pure" resin extract. The solvents typically used in making hop extracts are ethanol alcohol (predominantly used in Europe) and "organic" solvents (hexane). These solvent extracts are increasingly falling out of favor worldwide due to perceived problems with the residues.
Click on the following topics for more information on hops.