Chapter 10

Wort Boiling

Kettle Additives


Hops or hop products are introduced to the brewing process during boiling. Depending on when the hops are added to the boil, they can contribute the characteristic bitter flavor or provide the characteristic aroma and flavor to beers. The brewer has many options that determine the final profile of the hops in the beer. Hops give beers the crisp, citrusy flavor found in pale ales, the bitter taste of a stout, and the characteristic aroma of India pale ales (IPAs). Even in beers such as browns and porters where hops aren’t as pronounced, the addition of hops help increase the shelf life of the final product and provide a taste balance with the alcohol in the beer.

Timing of Addition

The hops may be added all at once; but more commonly, they are metered out in portions throughout the boil either at the start of the boil or near the end of the boil known as finish hopping. Bittering hops are usually added at the beginning of the boil to maximize isomerization of their alpha-acid content. Hops are added early in the boil to aid in the precipitation of proteins, thus providing a cleaner fermentation. Moreover, if hops are added early in the boil, undesirable volatile components (e.g., myrcene) are driven off (Kunze, 1996). On the other hand, some brewers prefer boiling the wort vigorously for 15 to 30 minutes before adding hops to minimize the precipitation of alpha-acids.

Finish Hopping

The primary method used to get hop flavor and aroma in the beer is to add hops very late in the boil or even to the whirlpool for a distinct and intensive hop aroma. This practice is called “late hopping,” “late kettle hopping,” “aromatic hopping,” or “finish hopping.”

Whole Hops

Some brewers prefer using whole hops to achieve optimal flavor and aroma in finish hopping, while others prefer to use non-isomerized hop pellets or kettle extract because of the short contact time. When whole hops are used for finishing, it takes a certain amount of time for the oils to be extracted from the lupulin glands; with pellets, though, the oil is readily available.

Dosing Procedures

In smaller breweries, whole hops or pellets are manually added to the kettle. Direct addition of hops to the kettle through the manway door is possible. When hops are added to the kettle, the heat should be shut off or the hops added very slowly to prevent a boil-over. Breweries using whole hops must use a hopjack or a hop strainer when casting the wort to remove spent hops.

Dosage Rate

The quantity of hops is determined by several factors: alpha-acid content, desired hop flavor and aroma in the finished beer, condition of the hops, efficiency of the hop extraction, brewing process, and type of brewing water. The hopping rate for bitterness can be calculated, whereas the rates at which hops should be added for flavor and aroma are less accurate.

Copper Finings

One way of enhancing floc formation is through the addition of copper finings. Copper finings (also referred to as kettle finings, carrageenan, or Irish moss) is a form of seaweed consisting mostly of a complex starchy polymer called K-carrageenan. K-carrageenan, like polyphenols, has a negative charge and is effective in precipitating positively-charged proteins from the wort solution. Use of carrageenan is helpful in some cases—especially with ales that have not been given a protein rest—and is common in the United Kingdom.

Dosage Rate

Dosage rate is normally 1 to 6 g/hL (10–60ppm) and is related to the protein content of the intended wort (Fratianni et al., 2017). The major reasons for the widely differing rates of use are variations in grist formulations, mashing systems, and specific gravities of the wort (Mathew, 1986). A higher dose rate is needed with higher gravity beers, and a lower dose rate can be applied if adjuncts are used. Exceeding the optimum dosage rate will not improve clarification, but it can lead to increased acidity of the wort during fermentation because of the carryover of unused moss into the kettle.e in the packaged beer. DMS gives beer a strong “sweet corn” or “lagery” flavor.

Choice of Material

Copper fining products come in a range of physical forms and degrees of purification, including powders, tablets, granules, refined carrageenan, and alkali-washed seaweed. Refined copper finings generally produce brighter clarified worts than do alkali washed products, and have lower optimum dosage rates.

Wort pH

Wort pH has a significant effect on fining performance, with a pH of approximately 5.0 required for efficient fining, and worts below pH 4.5 failing to fine.

Timing of Addition

Timing the addition of copper finings is essential because k-carrageenan denatures and becomes less active with prolonged treatment at high temperature. The addition must, therefore, be timed to ensure that the copper finings dissolve completely but do not denature.

Dosing Procedures

Powdered products are usually thoroughly mixed in cold water to provide a suspension that can then be added directly to the kettle or the whirlpool. If powdered products are added directly to the kettle, there is likelihood that a significant amount of product will be sucked up the chimney, which results in under-dosing and loss of performance (Vernon, 1985).


Some brewers add tannic acid to reduce hop-bittering utilization, to reduce color reactions, and to improve wort clarity through enhancement of hot break formation.

Calcium Sulfate or Calcium Chloride

Calcium sulfate (gypsum) or calcium chloride is often added to lower the pH of the wort during the boil by 0.1 to 0.2 units (Briggs et al., 2004). The calcium ion reacts with phosphates and polypeptides to form insoluble compounds releasing hydrogen ions.

Syrups and Sugars

Syrups and sugars can be added to the kettle in either dry or liquid forms. They are called “wort extenders” since they increase the extract without little or no added investment in brewhouse vessels.

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