| Abstract |
- The following two projects have been carried out to clarify the impact of these foam
stabilizers, and to compare their foam stabilizing power to one another as well as the
cling ability.
The first project investigated the impacts of four commercially available hop-
derived foam stabilizers; iso-alpha-acid (Iso), rho(dyhydro)-iso-alpha-acid (Rho),
tetrahydro-iso-alpha-acid (Tetra), and hexahydro-iso-alpha-acid (Hexa). Foam
stabilizing properties and cling formation patterns were investigated using an
unhopped lager beer. Unhopped lager was dosed with Iso, Rho, Tetra, and Hexa,
separately, over a range of concentrations from 2 to 10 ppm. Uniform foam was
created by Inpack 2000 Flasher Head, and was measured by Nibem Foam Stability
Tester (NIBEM-TPH) followed by Nibem Cling Meter (NIBEM-CLM) to determine
the relationship between the concentration and Nibem-30 as well as the cling
formation ability of each compound. The foam stabilizing power was determined to
be Tetra, Hexa, Iso, and Rho from the strongest to weakest. Linear regression models
were created using the NIBEM-TPH dataset, and based on the 95% confidence
interval analysis, the foam stability of Tetra or Hexa becomes significantly larger than
that of Iso when 2.4 ppm or 4.2 ppm of Tetra or Hexa was used, respectively. Cling
formation patterns could be considered into three groups: "ring," "mesh," and
"powdery." The control beer had the lowest foam stability and did not show any cling
on the glass.
The second project focused on three topics; the binary effects of foam stabilizers,
comparison of non-hop and hop based foam stabilizers, and method comparison.
Foam stabilizing properties and cling formation patterns of lager beer to which Tetra,
Hexa, and PGA were added were investigated. Four series of base beers were
prepared to achieve approximately 0, 4, 8, and 12 ppm of Iso to an unhopped lager
beer. On top of each of these, Tetra, Hexa, and PGA were added over a realistic
concentration range to create the samples with two different foam stabilizers. Foam
stability results, NIBEM30 and Foam Stability Figure (FSF), for each sample was
measured using a Nibem Foam Stability Tester (NIBEM-T) and a Steinfurth Foam
Stability Tester (Steinfurth-FST), respectively. Percentage of beer foam clings to the
glass side walls after Nibem-T analysis was measured using Nibem Cling Meter
(NIBEM-CLM). Multiple linear regression models were created for both NIBEM30
and FSF, and the relative foam enhancing strengths of four compounds were
compared. Between the two methods employed, the magnitude of foam stabilizing
power of each compound was different, especially in the case of PGA. This is
presumably due to the difference in the parameters measured, i.e. foam collapse by
Nibem and liquid drainage by Steinfurth. When Steinfurth-FST was used, PGA
showed much better foam stabilizing ability compared to that of NIBEM. In the
investigated range, the foam stabilizing effects of these compounds were found to be
additive for both NIBEM and Steinfurth, though FSF results showed somewhat
hyperbolic tendency.
Overall, positive impacts of all foam stabilizers were confirmed over the
investigated range of concentrations in two different methods. The degree of foam
stabilizing strength varies between compounds. Among the hop-derived foam
stabilizers, the foam stabilizing ability was found to be ordered as Tetra/Hexa, Iso,
and Rho from the strongest to weakest. Tetra and Hexa had approximately same
degree of stabilizing power. Hop-derived foam stabilizers showed an excellent ability
to generate cling while PGA had a minimal effect. Steinfurth, liquid drainage method,
was much more sensitive to the foam stabilized by PGA, and relatively less sensitive
to the hop derived foam stabilizers.
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