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Ultrasound Food Testing

THE FOODLINK PROGRAMME - PARTICIPANTS

The Foodlink programme involved four food companies in a collaborative project, funded by DEFRA (Department for Environment, Food and Rural Affairs). The four companies were Kerrygold, Cadbury Ltd, Westlers Foods and BakeMark UK.

The objective was to investigate whether air-coupled ultrasound could be used to distinguish one type of food material from another, and to find foreign bodies and contaminants within food. The aim was then to produce a portable system that could be used on-line for food quality control applications.

IMAGING IN FOOD

The apparatus used below could be used to scan objects in air, without the need for contact and contamination.


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Apparatus for scanning food samples in through-transmission

The first example is a piece of mint, included within a uniform chocolate sample. The presence of the mint fragment is clearly visible, using either the amplitude of the signal or the time-of –flight through the sample.

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Chocolate sample containing a single 1.5 mm x 2 mm piece of mint “sweet”.


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Wood Rubber



2mm wide contaminants placed within cheese, using (top) amplitude and (bottom) time-of-flight.

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Chocolate bar samples, showing the “squares”. Left – chocolate only; right – chocolate containing raisins, seen as the darker areas.


SCANNING AND IMAGING OF CONTAINERS

Tomgraphic imaging inside a drinks container

Scanned transducers can be used to reconstruct tomographic acoustic images of the contents of containers. It can also be used to study changes in the foodstuff, for example coagulation of the contents.

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Ultrasonic liquid level detection

The system can be used to detect the level of a liquid inside an optically opaque container. Here we see the results of scanning the transducer pair vertically down the container. The signal disappears when the transducers are above the height of the liquid.


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Coagulation of palm oil

This can be detected by measuring the ultrasonic amplitude, spectral content and time-of–flight as a function of time.

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SYSTEM FOR USE ON CONVEYOR BELTS

A photograph of our system is shown below, with the pulse compression output both through air and in the presence of a container. Note that latter arrives earlier due the faster velocity within the filled metal can.

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