Size-Dependent Variability in Flow and Viscoelastic Behavior of Levan Produced by Gluconobacter albidus TMW 2.1191
1
Chair of Technical Microbiology, Technical University of Munich, Gregor-Mendel-Straße 4, 85354 Freising, Germany
2
Department of Food Technology and Food Material Science, Technical University of Berlin, 14195 Berlin, Germany
3
Anton Paar Germany GmbH, Hellmuth-Hirth-Strasse 6, 73760 Ostfildern-Scharnhausen, Germany
4
Lehrstuhl für Systemverfahrenstechnik, Technische Universität München, Gregor-Mendel-Straße 4, 85354 Freising, Germany
5
Division of Food Chemistry, Institute of Chemistry, Martin-Luther-University Halle-Wittenberg, 06120 Halle (Saale), Germany
6
Department of Food Chemistry and Phytochemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
*
Author to whom correspondence should be addressed.
Foods 2020, 9(2), 192; https://doi.org/10.3390/foods9020192
Received: 9 December 2019
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Revised: 5 February 2020
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Accepted: 11 February 2020
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Published: 14 February 2020
(This article belongs to the Special Issue Microbial Exopolysaccharides in Foods: New Aspects of the Interplay between Structure and Function, and Implications on Product Quality)
Levan is a fructan-type exopolysaccharide which is produced by many microbes from sucrose via extracellular levansucrases. The hydrocolloid properties of levan depend on its molecular weight, while it is unknown why and to what extent levan is functionally diverse depending on its size. The aim of our study was to gain deeper insight into the size-dependent functional variability of levan. For this purpose, levans of different sizes were produced using the water kefir isolate Gluconobacter albidus TMW 2.1191 and subsequently rheologically characterized. Three levan types could be identified, which are similarly branched, but differ significantly in their molecular size and rheological properties. The smallest levan (<107 Da), produced without adjustment of the pH, exhibited Newton-like flow behavior up to a specific concentration of 25% (w/v). By contrast, larger levans (>108 Da) produced at pH ≥ 4.5 were shear-thinning, and the levan produced at pH 5.0 showed a gel-like behavior at 5% (w/v). A third (intermediate) levan variant was obtained through production in buffers at pH 4.0 and exhibited the properties of a viscoelastic fluid up to concentrations of 15% (w/v). Our study reveals that the rheological properties of levan are determined by its size and polydispersity, rather than by the amount of levan used or the structural composition.
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Keywords:
levan; Gluconobacter; exopolysaccharide; hydrocolloid; molecular weight; rheology
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MDPI and ACS Style
Hundschell, C.S.; Braun, A.; Wefers, D.; Vogel, R.F.; Jakob, F. Size-Dependent Variability in Flow and Viscoelastic Behavior of Levan Produced by Gluconobacter albidus TMW 2.1191. Foods 2020, 9, 192. https://doi.org/10.3390/foods9020192
AMA Style
Hundschell CS, Braun A, Wefers D, Vogel RF, Jakob F. Size-Dependent Variability in Flow and Viscoelastic Behavior of Levan Produced by Gluconobacter albidus TMW 2.1191. Foods. 2020; 9(2):192. https://doi.org/10.3390/foods9020192
Chicago/Turabian StyleHundschell, Christoph S., Andre Braun, Daniel Wefers, Rudi F. Vogel, and Frank Jakob. 2020. "Size-Dependent Variability in Flow and Viscoelastic Behavior of Levan Produced by Gluconobacter albidus TMW 2.1191" Foods 9, no. 2: 192. https://doi.org/10.3390/foods9020192
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