The effects of freezing and thawing on the structure, rheology and associated physical properties of galactomannan solutions for food applications

Foods are complex multi-phase structures characterized by wide ranges of length and time scales. For most food products, the aim is to increase sustainability, health and ethical credentials without compromising on customer experience or cost. To achieve this, a thorough understanding of the relevant food matrices on microscopic and molecular scales is necessary. Thus, advanced physical characterisation and analysis approaches are required to determine how different conditions affect the local structure and rheological response throughout the materials. Galactomannans, such as locust bean or guar gums, are important food polymers due to their strong thickening, stabilizing, and gel-forming properties. They combine a relatively hydrophobic backbone with more hydrophilic side-chains whose distribution controls the formation of superstructures such as aggregates or hyperentanglements.<br /> <br /> The project outcome is a detailed understanding of how galactomannans are affected by freezing and subsequent thawing, both in aqueous solution and in the presence of sugars (sucrose, glucose etc). As a solution freezes, polymer/sugar are expelled from the growing micro-crystals (approximately equal to 50 microns) resulting in strong changes in local structure and rheology, and in effects such as cryo-gelation. Of particular interest is how gel structures disassemble during thawing. The local rheological response of the interstitial space varies with polymer and solute composition, and measurements at this scale can only be achieved using micro-rheology. Recent advances in the Mattsson and Connell research groups include combining active (magnetic) and passive (thermal) particle tracking and Differential Dynamic Microscopy analysis, dramatically broadening the dynamic range. This will be complemented by fluorescence lifetime microscopy of molecular rotor dyes, bulk rheology, light scattering and electron microscopy. Some of these microscale measurements will be cross-correlated for the first time, and advances in this area will have broader applications in fluid mechanics measurements in other fields such as medicine (blood, thrombosis) and the drying of virus loaded droplets.

<p>The project addresses the key societal and industrial question of developing more sustainable and healthier food matrices, strongly linking to the capabilities of the Bragg Centre. The application of fundamental soft matter science to foods strengthens the interdisciplinary profile and impact of the School, resulting in more 4* outputs (REF), establishing Leeds as a leading centre for soft matter science. Relevant EPSRC research areas include: biophysics and soft matter physics, biological chemistry, complex fluids and rheology, and polymer materials, and the research links to the EPSRC CDT in Future Fluid Dynamics, and the National Alternative Protein Innovation Centre (NAPIC).</p>

<p>Formal applications for research degree study should be made online through the University’s website. Please state clearly in the Planned Course of Study section that you are applying for <em><strong>EPSRC DTP Engineering & Physical Sciences</strong></em> (if you do not apply under this programme code, your application will not be considered), in the research information section that the research degree you wish to be considered for is <em><strong>The effects of freezing and thawing on the structure, rheology and associated physical properties of galactomannan solutions for food applications</strong></em> as well as <a href="https://eps.leeds.ac.uk/physics/staff/4117/dr-johan-mattsson">Dr Johan Mattsson</a> as your proposed supervisor<em><strong> </strong></em>and that the funding you wish to be considered for is <em><strong>EPSRC Faculty Doctoral Landscape Award 2026/27: Physics & Astronomy</strong></em>.</p> <p>Applications will be considered after the closing date of Friday 27 February 2026.  Potential applicants are strongly encouraged to contact supervisors for an informal discussion before making a formal application. We also advise that you apply at the earliest opportunity as the application and selection process may close early, should we receive a sufficient number of applications or that a suitable candidate is appointed.</p> <p>Please note that you must provide the following documents in support of your application by the closing date of Friday 27 February 2026:</p> <ul> <li>Full Transcripts of all degree study or if in final year of study, full transcripts to date including grading scheme</li> <li>Personal Statement outlining your interest in the project</li> <li>CV</li> </ul> <p>If English is not your first language, you must provide evidence that you meet the University's minimum English language requirements (below).</p> <p><em>As an international research-intensive university, we welcome students from all walks of life and from across the world. We foster an inclusive environment where all can flourish and prosper, and we are proud of our strong commitment to student education. Across all Faculties we are dedicated to diversifying our community and we welcome the unique contributions that individuals can bring, and particularly encourage applications from, but not limited to Black, Asian, people who belong to a minority ethnic community, people who identify as LGBT+ and people with disabilities. Applicants will always be selected based on merit and ability.</em></p>

Applicants to research degree programmes should normally have at least a first class or an upper second class British Bachelors Honours degree (or equivalent) in an appropriate discipline. The criteria for entry for some research degrees may be higher, for example, several faculties, also require a Masters degree. Applicants are advised to check with the relevant School prior to making an application. Applicants who are uncertain about the requirements for a particular research degree are advised to contact the School or Graduate School prior to making an application.

The minimum English language entry requirement for research postgraduate research study is an IELTS of 6.0 overall with at least 5.5 in each component (reading, writing, listening and speaking) or equivalent. The test must be dated within two years of the start date of the course in order to be valid. Some schools and faculties have a higher requirement.

<p>A highly competitive EPSRC Faculty Doctoral Landscape Award, in collaboration with the Magnum Ice Cream Company, providing full academic fees, together with a tax-free maintenance grant at the standard UKRI rate (£20,780 in academic session 2025/26) for 3.5 years.  Training and support will also be provided.</p> <p>This opportunity is open to UK applicants only.  All candidates will be placed into the EPSRC Faculty Doctoral Landscape Award Competition and selection is based on academic merit.</p> <p>Please note that there is 1 funded place available.  If you are successful in securing an academic offer for PhD study, this does not mean that you have been successful in securing an offer of funding.</p> <p>Please refer to the <a href="https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.ukcisa.org.uk%2F&data=05%7C02%7CJ.S.Hewer%40leeds.ac.uk%7C07632c93c06a442dca3d08ddfc172939%7Cbdeaeda8c81d45ce863e5232a535b7cb%7C0%7C0%7C638943898649349324%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=nylGSov8jOc7hr6X%2FmfnfQPecbVUnGqgoSqVgPGy5K0%3D&reserved=0">UKCISA</a> website for information regarding Fee Status for Non-UK Nationals</p>

<p>For further information about your application, please contact PGR Admissions by email to <a href="mailto:phd@engineering.leeds.ac.uk">phd@engineering.leeds.ac.uk</a></p> <p>For further information about this project, please contact Professor Fiona Meldrum by email to <a href="mailto:K.J.L.Mattsson@leeds.ac.uk">K.J.L.Mattsson@leeds.ac.uk</a></p>