Judith Wemmer


Last Name

Wemmer

First Name

Judith

ORCID

0000-0002-9103-2950

Organisational unit

Filters

2017 - 2019102020 - 20212
Reset filters

Search Results

Publications 1 - 10 of 12
  • Full spatio‐temporal elucidation of sheared multiphase materials
    Item type: Other Conference Item
    Gstöhl, Stefan J.; Schlepütz, Christian M.; Wemmer, Judith; et al. (2019)
    Book of Abstracts. HSR-2019: 9th International Meeting of the Hellenic Society of Rheology Pythagorion, Samos, Greece, 23-27 June, 2019
  • Integration of laccase-mediated cross-linking of pectin in a high-pressure foaming process
    Item type: Other Conference Item
    Wemmer, Judith; Holtgrave, Sarah; Michel, Martin; et al. (2018)
    Book of Abstract of the 32nd EFFoST International Conference
  • Fabrication of a Novel Protein Sponge with Dual-Scale Porosity and Mixed Wettability Using a Clean and Versatile Microwave-Based Process
    Item type: Journal Article
    Wemmer, Judith; Malafronte, Loredana; Foschini, Socrates; et al. (2021)
    Materials
    An open-porous protein sponge with mixed wettability is presented made entirely from whey proteins and with promising applications in biomedicine, pharmaceutical, and food industry. The fabrication relies on an additive-free, clean and scalable process consisting of foaming followed by controlled microwave-convection drying. Volumetric heating throughout the matrix induced by microwaves causes fast expansion and elongation of the foam bubbles, retards crust formation and promotes early protein denaturation. These effects counteract collapse and shrinkage typically encountered in convection drying of foams. The interplay of high protein content, tailored gas incorporation and controlled drying result in a dried structure with dual-scale porosity composed of open macroscopic elongated foam bubbles and microscopic pores in the surrounding solid lamellae induced by water evaporation. Due to the insolubility and mixed wettability of the denatured protein network, polar and non-polar liquids are rapidly absorbed into the interconnected capillary system of the sponge without disintegrating. While non-watery liquids penetrate the pores by capillary suction, water diffuses also into the stiff protein matrix, inducing swelling and softening. Consequently, the water-filled soft sponge can be emptied by compression and re-absorbs any wetting liquid into the free capillary space.
  • Full-volume elucidation of complex multiphase materials in controlled flow
    Item type: Other Conference Item
    Gstöhl, Stefan; Schlepütz, Christian M.; Wemmer, Judith; et al. (2018)
  • Full spatio-temporal elucidation of sheared multiphase materials
    Item type: Other Conference Item
    Gstöhl, Stefan J.; Schlepütz, Christian M.; Wemmer, Judith; et al. (2019)
  • Quantitative structure elucidation of sheared multiphase materials
    Item type: Other Conference Item
    Gstöhl, Stefan J.; Schlepütz, Christian M.; Wemmer, Judith; et al. (2019)
  • Enzymatic cross-linking of pectin in a high-pressure foaming process
    Item type: Journal Article
    Wemmer, Judith; Holtgrave, Sarah; Wiest, Laura; et al. (2020)
    Food & Function
    The enzyme laccase is a copper-containing oxidoreductase with the ability to oxidize a wide range of substrates, such as ferulic acid. Thus, the ferulic acid-containing sugar beet pectin (SBP) can be cross-linked through laccase-mediated oxidation. As cross-linking increases viscosity, it could be applied to stabilize SBP-containing foams. In this study, laccase-mediated cross-linking of SBP was investigated under conditions of a high-pressure foaming process. Shear, presence of CO2, and pressure were simulated in a rheometer equipped with a high-pressure cell. At rest, addition of laccase to SBP solution led to the formation of a stiff gel. Application of shear upon mixing of laccase and SBP solution decreased the storage modulus with increasing shear duration and shear rate. This can be attributed to the formation of a fluid gel. However, when shear was stopped before all available ferulic acid groups were cross-linked, a stronger and more coherent network was formed. Pressure exerted by CO2 did not affect cross-linking. Additionally, this approach was tested in a stirred high-pressure vessel where SBP was foamed through CO2 dissolution under pressure and shear followed by controlled pressure release. While pure SBP foam was highly unstable, addition of laccase decelerated collapse. Highest stability was reached when laccase and SBP were mixed prior to depressurization. At the point of foam formation, the continuous phase was thereby viscous enough to increase foam stability. At the same time, continuation of cross-linking at rest caused gel templating of the foam structure.
  • Liquid phase migration in foam extrusion of cellulose paste
    Item type: Other Conference Item
    Wemmer, Judith; Windhab, Erich J. (2017)
  • Effect of foaming on mechanical properties of microfibrillated cellulose-based porous solids
    Item type: Journal Article
    Wemmer, Judith; Gossweiler, Elias; Fischer, Peter; et al. (2019)
    Cellulose
    All-cellulose porous solids have been prepared by foaming watery suspensions of microfibrillated cellulose (MFC) and the foaming agent methyl cellulose (MC) followed by freeze-drying. Mechanical and structural characterization of foamed and unfoamed porous solids with and without MC was performed to evaluate the effect of the foaming agent and of the foaming process. In unfoamed systems, partial replacement of MFC by MC led to decreased mechanical stability and a stronger dependency of mechanical properties on density. The foaming process allowed to reach gas volume fractions of up to 52% through interfacial stabilization by MC and thus reduce specific volume of water before drying by half. The incorporated gas bubbles withstood the freezing and drying process as shown by scanning electron microscopy of freeze-dried samples. Final density and porosity were tailored by adjusting solid content in the suspension, foaming time or concentration of foaming agent. In uniaxial compression, foamed porous solids showed similar or even higher Young’s modulus and yield stress compared to unfoamed systems at same composition and density. In foamed porous solids with increased mechanical stability, X-ray μ-computed tomography revealed the occurrence of aligned tubes, which act as reinforcing substructure. Thus, foaming can be applied prior to freeze-drying to drastically reduce water content, while the mechanical performance is unaffected or even improved through restructuring.
  • Full spatio-temporal elucidation of sheared multiphase materials
    Item type: Other Conference Item
    Gstöhl, Stefan J.; Schlepütz, Christian M.; Wemmer, Judith; et al. (2019)
    Abstract Book of the 8th International Symposium on Food Rehology and Structure (ISFRS 2019)
Publications 1 - 10 of 12