After boiling, the next step is to separate the hop debris and trubaceous matter (hot break) to ensure that the wort is clear and bright before cooling. If whole hops are used, the weight of spent hops will be between 0.7 and 1.4 kg per hectoliter of wet weight, and the trub will weigh around 0.21-0.28 kg per hectoliter. The hot break will contain 80-85% crude protein, 20-30% tannin, 15-20% resins, and 2-3% ash.
Separation of Whole Hops
The methods for separating whole hops vary greatly. In smaller breweries, the hops are removed by filtering the wort through a cloth bag or a sieve. In larger breweries, several whole hop separation systems are used, such as a hop back or hop separator.
A more sophisticated device used for separating whole hops is the hop back, which resembles a mash tun and is commonly used by British brewers. The wort from the kettle is transferred into the hop back and strained through the slotted base.
Hop Separator (Strainer)
The hop separator or strainer is only used in large-scale breweries where whole hops are employed. It is an apparatus with a primary screen or slotted plates through which the majority of the wort flows.
Separation of Hot Trub
If pellets or extract are used, the wort can be clarified by sedimentation in a coolship, settling tank, centrifuge, or more commonly, a whirlpool or combined kettle/whirlpool. It is recommended to clarify the wort at the highest possible temperature to achieve optimal trub removal.
In the traditional method, the wort is cooled in shallow open vessels called coolships. The boiling wort is poured to a depth of 15 to 35 cm, allowing the hot break to settle out, followed by the precipitation of some cold break. The wort remains in the coolship for 1 to 3 hours (depending on conditions), and in some cases up to 12 hours, cooling to approximately 60 and 77°C.
Settling tanks, which have flat or conical bases, are the successors to coolships. They require less space due to their greater depth and are enclosed to minimize the risk of microbiological contamination. They are often equipped with coil or jacket cooling systems.
Occasionally, the wort is clarified through centrifugation, where high-speed spinning forces the hop and trub debris to the sides of the vessel. If the wort is heavily hopped, it may be necessary to pre-treat it with a strainer to remove some of the rough hop solids.
The whirlpool method is widely used for removing hot trub, particularly in breweries that use hop pellets, powder, and extracts. Whirlpools cannot be used with whole hops unless a hop back or strainer is used initially.
The latest development in small brewhouses is the use of a combined whirlpool and brew kettle. This vessel, as its name suggests, is used for both wort boiling and as a whirlpool. It can have an external wort boiler or calandria and no internal fountain or spreader. One external heater can supply two kettles, with one acting as a whirlpool and the second one used as a kettle.