Olive Oil Adulteration and Detection Methods
Adulteration in edible oils is quite common. Even in countries with most stringent of laws and regulations, adulteration has not gone away. In India, most of the olive oil is imported, particularly from the European countries hence its adulteration is unheard of in India. Therefore, to know about the problem of olive oil adulteration, it is important to know different ways in which this is done in these countries.
What is olive oil adulterated with?
1/3. Adulteration with other oils
Olive oil is one of the highest demanded and most expensive edible oils in the world. But, the production of virgin or extra virgin olive oil does not match the demand.
“While less than 10% of world olive oil production meets the criteria of extra-virgin (EVOO), it is estimated that up to 50% of retail oil is labeled extra-virgin – Source Wikipedia
This makes it quite lucrative for producers to adulterate virgin olive oil (VOO) and extra virgin olive oil (EVOO) with other oils or inferior quality olive oil so as to meet demand and earn high profits.
It is quite common to find VOO and EVOO adulterated with soybean, corn, safflower, sunflower and sesame oil. In some instances, colza oil with added colour and flavour has been labeled and sold as olive oil.
2/3. Adulteration with Inferior Olive Oil
The inferior quality lampante olive oil, or “lamp oil,” which is made from spoiled olives fallen from trees, is also used as an adulterant. It should be noted that this oil is prohibited to be sold legally as food in Europe.
Even low-grade soy oil and canola oil, coloured with industrial chlorophyll, and flavoured with beta-carotene have also been used as adulterants.
3/3. Labelling Malpractices
There is a tendency among the olive oil companies to label this oil in such a way as to circumvent the regulations and still sell the adulterated oil. Consumers want to know the country of origin of the olive oil which is in the bottle. Therefore, the regulations mandate labelling to incorporate the name of countries from which the oil has been obtained and its ratio on same side of the label. The European Union regulates the use of different “protected designation of origin” (PDO) labels for olive oils. However, this rule is circumvented by publishing names on different sides with the most popular country name being used prominently, even though it might have very little content of oil from that country.
Generally, the Italian VOO and EVOO is highly priced because of its top quality and popularity among the people. However, when products are a mixture of olive oil from more than one nation, it is not clear what percentage of the olive oil is really of Italian origin.
This type of malpractices exist, which, though is not strictly adulteration but the consumers do not get value-for-money and they are hoodwinked.
How to detect this adulteration?
It is not practically possible to check adulteration of olive oil with other oils or inferior quality olive oils at home in a reasonable manner. The only way which one can try is the swirl the bottle after opening and smell it. If it does not smell good or like olive oil, it should not be used.
However, there are many ways in which adulteration can be checked in labs. The detection of olive oil adulteration is complex process as no single test might be sufficient. A number of tests are used to determine olive oil authenticity and identity of the adulterant. These tests include determination of free acidity, steroidal hydrocarbons, peroxide value, sterol composition, triglyceride composition, UV extinction, fatty acid composition, wax content and the Bellier test. Chromatography, mass spectrometry and spectroscopy are also used to find adulteration.
The chart given below tells the different methods used to check adulteration in the laboratories…
| Method | Objective | Adulterant |
| NIR | Quantification | Soybean Oil |
| FTIR | Quantification | Soybean Oil |
| Raman | Quantification | Soybean Oil |
| NIR | Quantification | Olive Pomace Oil |
| FTIR–ATR | Quantification | Olive Pomace Oil |
| Raman | Quantification | Olive Pomace Oil |
| FTIR–ATR | Detection | Peanut Oil |
| FTIR–ATR | Detection | Peanut Oil |
| FTIR–ATR | Detection | Hazelnut Oil |
| NIR | Quantification | Corn oil, sunflower oil, soya oil, walnut oil, and hazelnut oil |
| NIR | Detection | Corn oil, sunflower oil, soya oil, walnut oil, and hazelnut oil |
| FTIR–ATR | Detection | Corn-sunflower mixture, cottonseed, and rapeseed |
| HPLC | Detection | Soybean oil, corn oil, and sunflower oil |
| NMR spectroscopy | Detection | Lampanate olive oil, Refined olive oil |
A simple and reliable method is based on analysis of fatty acid ratios. Olive oil and other oils are composed mainly of triacylglycerols. Olive oil has higher level of oleic acid and less level of linoleic and linolenic acids than other vegetable and seed oils. Oleic acid is a monounsaturated, whereas linoleic and linolenic acids are polyunsaturated fatty acids. The ratio of linoleic and linolenic acid to oleic acid in olive oil can be used as a way to detect its adulteration with soybean oil and other seed oils such as corn, safflower, sunflower and sesame oil, which have a higher content of linoleic and linolenic acids and lower amount of oleic acid in comparison to olive oil.
A new method against olive oil adulteration has recently been developed. It makes use of artificial DNA barcodes. These consist of magnetically recoverable silica particles containing synthetic DNA sequences, which are added to the oil in very small amount and can be retrieved at any time for authenticity test by PCR/sequencing.
This method has many benefits. It is low-cost, sample preparation is minimal and requires minute volumes. It can be applied to any oil sample without specific procedure optimization.