|Gushing in beer is a very severe quality defect, that may be caused by
fungal components present in the brewing materials. In particular, species of the genus Fusarium,
that infect barley during growth in the field, or Aspergillus and Penicillium,
favoured by wet storage conditions, may secrete components causing gushing (fig. 1).
identity of gushing components is still unknown, but measures taken to avoid gushing
include evaluation of the mycological status of barley prior to malting combined with a
test for the gushing tendency of finished malt.
Carlsberg has established a fast, sensitive and specific immunological test for
detection of Fusarium in barley, based on antibodies to Fusarium
antigens produced during growth of the fungus (fig. 2). In a few hours, this method
quantifies even minute amounts of Fusarium antigens. In contrast to the viability
of Fusarium, these antigens are very stable during storage. Therefore, the
content of Fusarium antigens reflects the entire "history" of a sample
irrespective of storage time, while standard plate count tests may fail to detect
non-viable Fusarium and thus the risk of gushing factors already produced during
a previous growth phase.
A test for the gushing tendency of finished malt has also been developed, based on the
assumption that gushing components must be 1) water-soluble, 2) active and soluble after
boiling, and 3) active under conditions prevalent in beer. Therefore, gushing components
are extracted from malt (or other brewing materials) by blending with water. After
centrifugation of the suspension, the supernatant is boiled. A volume of beer is then
removed from bottles of regular beer and substituted by boiled supernatant. After
recapping the bottles, gushing potential is activated by a rocking regime (fig. 3). This
test can be completed within three days and is at least as sensitive as more time
consuming mini-brew tests.
Materials for these two tests can be purchased directly from Carlsberg. For further
information on reagents for evaluation of Fusarium in barley, please contact Pia
Vaag (firstname.lastname@example.org). For positive and negative control
samples for the gushing test, please contact Preben Riis (email@example.com).
Gushing of beer