Food fraud is surprisingly not a modern day problem. References to fraudulent food activity can be traced back as early as the Romans, but it is generally regarded as the Victorian’s who put food fraud on the map. History recognizes Frederick Accum as being the first person to attempt to expose the nature and extent, and indeed dangers, of food adulteration. It was only after his publication of A Treatise on Adulterations of Food and Culinary Poisons in 1820 that the extent of tampering of foods and ingredients was uncovered, although many choose to ignore his findings.
“The man who robs a fellow subject of a few shillings on a highway is sentenced to death,” wrote Accum, “but he who distributes a slow poison to the whole community escapes unpunished.” This still resonates today with scandals continuing to hit the headlines on everyday commodity products from honey to olive oil and more recently spices. There are certainly different consumer impacts to economic adulteration of food; it could result in an off tasting product or be a more serious food safety issue.
In this article, we review some of the problems faced by the industry and which analytical solutions can be adopted to help fight the battle against the fraudsters to ensure product quality and authenticity.
Detection of Adulterated Olive Oil
Olive oil remains one of the world’s most adulterated food products. While the creation and consumption of olive oil remains concentrated within the Mediterranean region, the global export of extra virgin olive oil is continuously growing as consumer demand increases. With changes in market dynamics, opportunities for fraudulent activity for financial profit become more prevalent; whether it is adulteration with cheaper more available vegetables based oils or falsifying the provenance of such oils.
The novel solution of Direct Sample Analysis (DSA) coupled to Time of Flight (ToF) mass spectrometer offers rapid measurement of olive oil adulteration, with minimal sample preparation. Edible oils are composed mainly of triacylglycerols, (TAGs) fatty acid esters with three long chain fatty acid groups. The mixture of fatty acids in the TAGs is characteristic for different oils with olive oil containing a higher ratio of oleic acid and lower ratio of linoleic and linolenic acids in the TAGs than other vegetable oils. While the levels of free fatty acids in good quality olive oil are low, acids are obtained for analysis by a chemical hydrolysis of the TAGs. The response ratio of linoleic to oleic acid and linolenic acid to oleic acid in the TAGs of olive oil can be used as a way to detect its adulteration with soybean oil and other seed oils such as corn, sunflower, and sesame oil.
Figure 1: Top: Mass spectra of olive oil diluted by a factor of 100 in negative mode using DSA/TOF. Bottom: Mass spectra of olive oil adulterated with 10% soybean oil diluted by a factor of 100 in negative mode using DSA/TOF.
In the DSA TOF analysis, ionized TAG molecules are easily fragmented to produce ions of the constituent fatty acids. The spectrum in Figure 1 shows these fragment ions and confirms that the response ratio of linoleic and linolenic acid to oleic acid was roughly a factor of two higher for olive oil adulterated with 10 percent soybean vegetable oil in comparison to pure olive oil. Figure 2 demonstrates how the response ratio for linoleic acid and linolenic acid to oleic acid increased as the adulteration of olive oil with soybean oil increased from 5 to 50 percent. This further confirmed that adulteration of olive oil with soybean oil can be detected with good confidence by measuring the response ratio for linoleic and linolenic acid to oleic acid with DSA-TOF.