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Spectroscopic measurement of structural changes in a hostile environment


Extrusion cooking processes are widely used in the EU for food and feed manufacture, including breakfast cereals, snacks, babyfoods and animal feeds. A fundamental feature of such processes is the modification of the physical structure of native starch in cereals or potato derivatives to control structure creation and nutritive qualities in the products In order to improve product quality and production efficiency, it is necessary to measure the changes in the starch. Currently fast accurate methods are required for use for process control on factories.

The objectives of the project were to investigate the feasibility of using fast spectroscopic techniques to follow the physical changes in the starch in extrudates, and if successful to demonstrate the possibilities for making such measurements in-line in an extrusion cooking process for feedback control.
It was shown that NIR spectroscopy can be used to monitor the important physical changes in the starch fraction of an extruded cereal product over the full range of processing from native to highly degraded forms. It will be possible to develop a simple on-line form of analysis based on a sample ground extrudate. The factorial in-line studies with an NIR probe also gave excellent results, which suggested that the NIR method could be developed for continuous monitoring and feedback controls in factory processes.
The first part of the programme involved the manufacture of special samples of six extruded cereals at CCFRA. These materials were characterised by viscosity and gel permeation chromatography and sent to the scientific partners. Identical sets of samples were analysed by the spectroscopic techniques at IFR (Raman), INRA (Near infra red) and University of Aveiro (Mid infra red). The most suitable method, NIR spectroscopy, was developed for in-line studies with the assistance of Perstorp Analytical. After preliminary trials to establish the methodology, a large scale factorial experiment was carried out to study the relationships between NIR at spectral wavelengths 1400-2000 nm and three variables, temperature, starch level and the physical form of the starch.


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Participants (3)

Institut National de la Recherche Agronomique (INRA)
Rue De La Géraudière
44026 Nantes
Institute of Food Research
United Kingdom

NR4 7UA Norwich
Campus Universitario De Santiago
3810-193 Aveiro/eixo