E-Thesis 276 views
Development of Rheometry for the Characterisation of Rapidly Gelling Strain Sensitive Materials / Alex Bulpitt
Swansea University Author: Alex Bulpitt
DOI (Published version): 10.23889/SUthesis.66309
Abstract
The rheological analysis and gel point determination of rapidly gelling strain sensitive materials presents many challenges. High levels of sample mutation and low torque responses associated with the small strains required to maintain linear viscoelastic measurements lead to erroneous rheological d...
| Published: |
Swansea, Wales, UK
2024
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Hawkins, Karl M. ; Curtis, Daniel J. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa66309 |
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| Abstract: |
The rheological analysis and gel point determination of rapidly gelling strain sensitive materials presents many challenges. High levels of sample mutation and low torque responses associated with the small strains required to maintain linear viscoelastic measurements lead to erroneous rheological data. Such artefacts can be overcome by applying high frequency multiwave tests such as Fourier Transform Mechanical Spectroscopy (FTMS), decreasing measurement times, and increasing torque response. However, operating at high frequencies can invalidate the assumption of performing measurements in the gap loading regime, introducing sample inertia. Current methods of correcting for sample inertia used by rheometer software involves an iterative process and knowledge of parameters including sample density and shearing gap. Herein, we find a discrepancy between the rheometer measured gap and the actual gap. This introduces errors in the inertia correction and calculated data, including parameters at the gel point. Therefore, a novel procedure for sample inertia correction is developed and validated for high frequency discrete sweeps and FTMS, based on finding an accurate gel point using bovine gelatine. The correction procedure was used as a tool in the determination of gel points, and its application for strain sensitive, rapidly gelling systems (gel times < 30 s) is demonstrated. The inertia correction procedure has the potential for characterising any gelling material where the linear range is small or unknown, through the application of low levels of strain. Finally, the gel point of a rapidly gelling, hybrid carrageenan-based gel was determined. This gel is used in the vegetarian softgel encapsulation process, a process with inherent difficulties due to changing rheological properties of the gel. Elucidation of the rheological behaviour at the gel point may prove useful as a marker for determining end properties of the softgels and serves as a consistency check for product quality at the earliest possible stages. |
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| Keywords: |
Rheology, fluid inertia, strain sensitive rheometry, rapid gelation, fluid inertia correction, gel point, gelatine, carrageenan |
| College: |
Faculty of Medicine, Health and Life Sciences |
| Funders: |
KESS 2 |