Graduate Thesis Or Dissertation
 

Foam enhancing properties of hop bitter acids and propylene glycol alginate

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/rr1722623

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  • 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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