In recent years, the use of hop extracts in industrial and home brewing processes as an alternative to hop cones or pellets usually added to wort during boiling has become increasingly popular. These extracts represent concentrated sources of bitter compounds, i.e., α- and β-acids, which are involved in some of the main reactions that take place in the wort and are responsible for the bitterness and the final quality of beer. This work aims at proposing a novel extraction technique, using a hydrofluorocarbon solvent in subcritical conditions; this process provided an extraction yield of 19% and an α-acid recovery of approximately 49% in 120 min of process. The α-acid isomerization kinetics of thermally treated hop extracts were studied and compared with those of both hop pellets and a CO2 extract. Laboratory scale tests showed that shorter boiling times were needed using hydrofluorocarbon and CO2 extracts (approximately 25 min and 34 min, respectively) to reach the same isomerization efficiency of 16.73%, achieved in 50 min of boiling with pellets. Moreover, the process was scaled up and the possibility of considerably reducing the conventional treatment times using hydrofluorocarbon extracts was confirmed: the same isomerization yield (9.1%) obtained after 50 min using the traditional procedure with hop pellets was reached in a shorter time of approximately 35 min in a pilot apparatus
Colucci Cante, Rosa
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