D. RIVEROS (1); (1) Katholieke University Leuven, Heverlee, Belgium
Poster
Gushing phenomenon is a serious concern in the brewing industry;
although is not necessarily an indicator of low quality or inadequate
processing, it represents a public image drawback with economic
consequences when it is observed. This study attempts to discover why
gushing tends to vary when different hydrophobins are used to induce it,
and how these differences could helps us to better understand the
gushing phenomenon. The interaction between hydrophobin monomers and
their posterior monolayer formation was investigated. Four different
hydrophobins were compared: HFBI and HFBII (Trichoderma reesei), hfb1-2a (Trichoderma harzianum), and FgHYD5 (Fusarium graminearum).
Gushing ability, adsorption to hydrophobic and hydrophilic surfaces,
and computer modeling simulation were performed to elucidate the
physical and spatial changes during self-assembly and nanobubble
formation. It was observed that hfb1-2a, HFBI, and HFBII were the
strongest gushing inducers, with only 3 µg/L necessary to induce
overfoaming in sparkling water, while more than 40 µg/L of FgHYD5 was
necessary to induce a similar amount of liquid. When mixtures of
hydrophobins were inoculated into sparkling water in equal parts, the
amount of liquid tended to be an average between the strongest and
weakest hydrophobin used, showing that there is interaction between the
protein monomers that creates weaker assemblies and decreases the
gushing potential of a strong inducer like hfb1-2a. When the
hydrophobins were deposited individually on hydrophobic and hydrophilic
surfaces, HFbi1-2a showed strong adsorption on hydrophobic surfaces due
to its well-defined hydrophobic patch; HFBI and HFBII showed a similar
behavior, exhibiting a preference for hydrophobic surfaces; FgHYD5, on
the other hand, showed a bigger preference for hydrophilic surfaces,
which was related to its less-defined hydrophobic patch and reduced its
ability to shape highly stable self-assembled monolayers similar to
Hfb1-2a. Protein interaction simulation showed that when dimers and
tetramers of Hfb1-2a are formed, large and uniform hydrophobic patches
are exposed, which explains why this hydrophobin interacts better with
hydrophobic surfaces and CO2 in the case of carbonated
beverages. Meanwhile, FgHYD5 in the same situation orients its molecules
differently, as well the area of its hydrophobic patch, which makes it
weaker when it interacts with hydrophobic elements. This study showed
that protein conformation and association have strong effects on
gushing. Knowing the weak points of these mechanisms can give us an
advantage in tackling it.
David Riveros received a B.S. degree in microbiology from Pontificia
Universidad Javeriana in Colombia, and in 2008, he earned his master’s
thesis in Valdivia (Chile) in wastewater treatment technologies. He
returned to Colombia where he worked in several food industries as a
quality control assistant and quality management advisor from 2008 to
2011. He is now pursuing his doctoral studies at Katholieke Universiteit
Leuven in Leuven, Belgium, under the supervision of Guy Derdelinckx. He
is working as part of a team fully devoted to understanding
nano-aspects of class 2 hydrophobins related to the primary gushing
phenomenon.
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