NMR Technology in Food Processing, Institute of Food Research, United Kingdom

NMR (nuclear magnetic resonance) or MRI (magnetic resonance imaging) has been developed as a major analytical methodology since it was first discovered in the 1950s. NMR spectroscopy is a technique exploiting the magnetic properties of certain chemical nuclei (any nucleus possessing magnetic spin).

Aside from the more usual chemical and imaging applications, the method is now being used to enhance the analysis in many other fields of industry.

The technique can give an indication of the chemical composition of an area of material or indeed give a contrast-free image of the activities during a process.

NMR has already been used for a number of applications in food processing technology, including: characterising the energetic status of cells to monitor the fermentation of yoghurts (using phosphorus 31 LR NMR), examination of cell cultures in the mashing of beer (using proton NMR), and the cooking of various types of rice (proton NMR).

ADVANTAGES

Although NMR is a relatively insensitive technique in these process applications, it is examining bulk properties and this does not matter. The technique can be used to examine processes and textures without the use of any marker compounds or indeed any physical incursion at all beyond a magnetic field.

NMR data can be used to increase understanding of processes such as enzymatic and conventional chemical reactions during a production process and also to supplement quality and process control during production.

NEW NMR SYSTEM FOR MULTI-SENSOR ANALYSIS

The Institute for Food Research in the UK has developed a new working prototype of a new type of NMR system, which allows multiple analyses to be carried out on the same sample simultaneously. The project has also included development of a low-cost MRI scanner and also an on line MRI sensor for use on conveyors in the food and pharmaceutical industries.

During food processing many samples can undergo rapid changes which are then irreversible. NMR would usually be ideal to monitor such changes but the conventional method has always relied on very strong magnetic fields, which could only be produced by a large super-conducting magnet using liquid helium cooled coils.

However, the IFR has now developed an open-access Halbach NMR spectrometer (using smaller powerful shaped magnets), which means that larger bulky samples can be examined. The Halbach system is cheap and easy to construct and is portable. It allows NMR/MRI technology to be successfully ported to the production line and used to provide continuous analysis.

The next step is to develop a multi-sensor system which can be combined with a range of other sensor systems such as FTIR (Fourier transform infrared), with X-rays and laser scattering techniques, impedance spectroscopy and electrochemical techniques.

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