In the hop addition process, brewers typically prefer not to use hop flowers but rather the pressed product formulated into pellets. These pellets are added during the boiling process for the reasons already described. In the case of microwave usage, the hop-related process occurs externally as a parallel process, not inside the main brew kettle. The products obtained are then inserted subsequently, because some of the reactions that take place during boiling with the traditional method occur in the microwave reactor.
In the traditional process, hops must be added before boiling because the isomerization of α-acids only occurs at high temperatures. In the case of microwaves, this reaction takes place during the extraction process. The equipment includes a glass reactor where hops are added with water, and then the microwave extraction process is initiated at a specific temperature for a predetermined time, allowing the formation of aromatic essential oil and the bittering fraction.
Given the conditions under which the extraction process takes place, the isomerization reaction has already occurred, so it is not necessary to add hops during the boiling phase. This applies to the bittering component, while the essential oil is added at the end of fermentation to preserve volatile substances.