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Dr Claudia Philipp

Previous Food Science PhD Candidate

Claudia Philipp


Ext (470) 4778
Location CO 5.23

Physicochemical behaviour of starch-protein mixtures during low-moisture extrusion

Supervised by Professor Indrawati Oey and Associate Professor Pat Silcock.


Claudia is from Berlin (Germany) and completed her Master’s degree in Food Engineering at Berlin University of Technology. During her final two years she has undergone two Industrial Traineeships at CSIRO, Australia.
Doing her PhD at Otago has been a great opportunity. The Department is welcoming and of an international calibre, exhibiting a diverse range of research.

Project Outline

Extrusion cooking has become a highly important processing technology that is used to obtain a wide range of processed food products such as breakfast cereals, ready-to-eat snack products and pet foods. During extrusion processing, primarily dry powdered starchy and/or proteinaceous food materials are subjected to a combination of low moisture (10 to 30 %), high temperatures (up to over 150 °C), high pressure (up to 25 MPa) and mechanical shear leading to molecular transformation and a variety of reactions including starch dextrinisation and protein denaturation.
These processes change and modify the physicochemical and functional properties of the extruded material. Extrusion cooking is accompanied by changes in the phyical state of the materials. The resulting plasticised food material is subsequently forced through a die and the pressure drop, which occurs across the die, results in a rapid change of material properties from rubbery/plactisicised to glassy.

To facilitate the production of nutritious extruded food products, improved extruder and process control is necessary. Automation and control during extrusion is difficult due to non-standardised reporting of extrusion control parameters and non-linearities that occur in product characteristics during processing, which complicate the application of model systems. Therefore, further research with focus on different extrusion process parameters and their impact on different physicochemical reactions such as starch dextrinisation and protein hydrolysis as well as material properties including rheology and glass transition temperatures is required to get a better understanding of the material-process interaction and, thus, to enable optimisation of the extrusion process.