3 September 2012
A suite of sophisticated molecular and stable isotopic techniques developed by organic chemists at the University of Bristol has proven to be a powerful diagnostic tool for analysing organic materials.
Originally developed to look at organic residues on archaeological materials, these analytical techniques are also proving useful in food science and forensics.
In the 1990s, Richard Evershed, Professor of Biogeochemistry, and his colleagues in the School of Chemistry, recognised that by combining molecular information with compound-specific isotopic signatures from organic residues, they could help answer fundamental questions about early human culture. Their analyses of residues left on ancient pottery have provided chemically-based evidence that dairying in Europe and the Near East dates nearly 9,000 years, which is 2,000 years earlier than previously thought.
These findings have furthered our understanding of early human interactions with animals and captured the attention of the public. Evershed has found that applying these same analytical tools in other areas has been equally impactful.
In 1995, he and his colleagues were approached by the UK food industry to develop techniques for detecting adulteration in commercial maize oil.
The authenticity of vegetable oil products is a serious issue within the food industry as the adulteration of high quality oils with lower quality oils not only constitutes economic fraud, it can also have serious health implications. However, it’s very difficult to determine the authenticity of maize oil with conventional analyses because its fatty acid composition overlaps with that of several other oil types, making it impossible to distinguish.
In 1995, the UK government’s Ministry of Agriculture, Food and Fisheries’ Working Party on Food Authenticity reported that of 79 samples of commercial maize oil collected from retailers, 35 per cent had been adulterated with undeclared oil.
Evershed and his colleagues applied the exact same techniques they were using in their analyses of ancient organic residues and found they were able to detect as little as 5 per cent adulteration in maize oil, which remains the best detection method to date.
As a result of the improved detection methods developed at Bristol, a follow-up report by the UK’s Food Standards Agency showed that of 61 commercial maize oil samples collected in 2001, none were adulterated with more than 5 per cent undeclared oil. This was a considerable improvement from the 35 per cent in 1995.
Evershed’s techniques are referenced in the Codex Alimentarius Commission standards (Codex Standard 210-1999), which is a global reference point for consumers, industry, national food control agencies and the international food trade.
“I was aware that the adulteration of commercial maize oil had decreased as a result of our new detection methods, but I only recently learned that it had become the international standard,” said Evershed. “As scientists we often put our research out into the public domain without fully realising how the information gets used and what impact it has.”
In 2003, Evershed’s analytical expertise was called upon by Metropolitan Police in relation to a murder investigation. The police had DNA evidence linking a missing individual to an area of disturbed soil, a suspected unearthed grave, in the back garden of a private residence. However, because the residence belonged to the missing individual, this line of inquiry was inconclusive.
Evershed once again applied his sophisticated analyses to organic residues collected from the disturbed soil; the first time anyone had tried to use stable isotopes on human lipids in a murder case. He was able to confirm that the residues were consistent with human body fat, which led to the confession of the murderer.
“I got a very nice letter from the family of the victim afterwards, thanking me for my contribution,” said Evershed. “It was very touching.”
The chemical analyses developed by Evershed and his colleagues at Bristol have ultimately grown out of NERC funded research.