Journal of the American Society of Brewing Chemists vol:72 issue:1 pages:12-21
Gushing is the vigorous overfoaming of carbonated beverages when the bottle is opened. Primary gushing in beer is mostly caused by a group of proteins called hydrophobins secreted by filamentous fungi, which contaminate CO2 gaseous molecules during carbonation and form nanobubbles. The influence of hop oil antifoam on primary gushing showed a complete suppressing effect in sparkling water, a decreasing effect in wort, and no influence on gushing-positive beers. This shows the importance of the critical point of addition of this product in the brewing process. GC and GC-MS analysis show that commercial available lipophilic hop extract comprises fatty acids, either saturated fatty acids (SFA) or unsaturated fatty acids (UFA) (both free and incorporated in mono-, di-, and triglycerides), waxes (long-chain alkanes), and steroid compounds. Gushing analysis of each compound showed that SFA and UFA behave in a different manner regarding gushing. In contrast to SFA and trans-form UFA, cis-form UFAs do not induce gushing. Long-chain alkanes provide sufficient hydrophobic structures to interact with gaseous CO2 molecules and induce gushing. Because hop antifoam molecules are hydrophobic, they interact with hydrophobins and prevent interaction with CO2 and,consequently, inhibit the possibilities of development of the explosive nanobubble structure.