Helping to resolve physical contamination in a food ready meal

An established food manufacturer, producing a wide range of popular ready meals for UK-wide distribution, needed help identifying foreign material found in one of their products.

The challenge

After receiving a product contamination complaint, our client needed to urgently identify the foreign material. A consumer had found what they believed to be a ‘fingernail’ in one of the company’s ready meals and was understandably distressed by its appearance in their food.


With brand reputation and consumer safety potentially at risk, the client asked RSSL’s Microscopy Team to carry out an immediate investigation so that appropriate action could then be taken.


We used several analytical techniques to determine the precise nature of the foreign material, leveraging our broad capabilities and extensive experience in physical contaminant identification to provide a reliable and accurate response. 

Figure 2: Image of a section of the sample, stained in Toluidine Blue, showing the presence of lacunae and    canaliculi – these structures are typical of bone.

Our approach

As a first step, we used stereo and light microscopy to examine the sample’s structure, size and shape. Initial results suggested that it was actually bone, rather than a fingernail, but we needed to delve deeper.  


Our technical experts took a thin section of the sample and stained it with toluidine blue. Analysis clearly showed the presence of lacunae, canaliculi and osteocytes; instantly recognisable as typical bone structure.


This was confirmed with the application of two additional microscopy techniques.


Fourier transform infra-red (FT-IR) spectroscopy

Using Fourier transform infra-red (FT-IR) spectroscopy to examine a subsample of the fragment, we found it contained bands assigned to protein and calcium phosphate but not amide (from keratin), which would indicate a fingernail. 



Figure 3 FT-IR spectrum of the sample material (red) compared with a library pentacalciumhydroxyphosphate spectrum (blue).




Figure 4 X-Ray Micrograph of bone sample.




X-ray microanalysis

By carrying out an x-ray microanalysis, we also determined that the sample contained a high level of calcium and moderate level of phosphorous. This elemental composition is consistent with the sample being bone which is a mineralised form of calcium phosphate.


But what was the source of the bone? The client needed a complete picture and asked RSSL’s DNA and Protein Team to identify the animal species.

With the capability to detect the DNA of up to 20 different species of meat and 50 species of fish at extremely low threshold levels, we carried out a further investigation to answer this crucial question. Our targeted DNA and protein testing quickly confirmed that the sample was, in fact, a fragment of chicken bone.



The outcome

Given that the ready meal in question was a chicken-based meal, the results of our detailed analysis showed that the product’s meat content was the source of the foreign material. These findings reassured the client that the complaint was not a contamination issue and did not demand a product recall.  A welcome outcome that saved them valuable time and resources. Armed with this information, they were able to respond to the consumer with a comprehensive report of our extensive analysis and findings. This not only demonstrated credible due diligence, it also helped to restore consumer confidence in the brand.

We were impressed by the speed and detail of RSSL’s response to our potential contamination crisis. The knowledgeable team carried out a thorough investigation and gave us the answers we needed to confidently resolve the issue.

UK Food Manufacturer




How RSSL can support with physical contamination investigations


RSSL is widely acknowledged as a world leader in foreign body identification. Our microscopy team have over 100 years of expertise, and have built up a database containing thousands of reference samples, which supports our work in analysing new incidents. We use highly sophisticated microscopy and spectroscopic techniques to identify physical contaminants and can provide rapid turnaround via our Emergency Response Service. We provide guidance on how to send samples for testing, and also advise on preventing foreign body incidents, as well as offering a pre-screening service that is useful for identifying sources of metal swarf should these arise in factory equipment. Click below to find out more or contact us via the contact form.

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