A curative method for primary gushing of beer and carbonated beverages : characterization and application of antifoam based on hop oils

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 CO ₂ molecules and induce gushing. Because hop antifoam molecules are hydrophobic, they interact with hydrophobins and prevent interaction with CO ₂ and, consequently, inhibit the possibilities of development of the explosive nanobubble structure.