Advertise
International olive oil expert and judge, and member of the Scientific Society – Alexandria University.
We have recently noticed the spread of a phenomenon promoting the idea that olive oil is authentic and unadulterated if it freezes when placed in the refrigerator, treating this as a home test for detecting adulteration. But this method is unscientific, and freezing olive oil is not considered a reliable measure for detecting adulteration. This is because the freezing process is affected by several factors such as the refrigerator temperature, the composition of the oil, and the proportion of saturated fatty acids in it.
Natural oils may freeze or solidify at low temperatures, while oils mixed with vegetable oils may remain liquid under the same conditions. But this is not conclusive proof of adulteration, nor does it eliminate the need for precise laboratory analyses to confirm quality. Therefore, relying on freezing the oil is considered an inaccurate method.
Different oils, including authentic olive oil, contain varying proportions of saturated fatty acids that cause the oil to freeze at different temperatures.
Among the most prominent of these acids are: palmitic acid (C16) and stearic acid (C18).
The proportion of saturated fatty acids in olive oil ranges between 7.5% – 25% of its total composition. The proportion is often:
These proportions depend on many factors, the most important being the number of cold hours the fruits are exposed to during oil formation; the more cold hours, the lower the proportion of saturated fatty acids.
The fatty acid composition of olive oil is affected by the temperatures the fruits are exposed to during oil formation. Higher temperature is directly correlated with an increase in saturated fatty acids.
There is also a relationship between fatty acids:
Analyses show an inverse relationship between MUFA and PUFA, which is reflected in the quality of the oil.
The freezing point of the oil differs according to the olive varieties used in production, in addition to the region of cultivation and its method (traditional, intensive, or super-high-density). Therefore, comparing one oil to another based on freezing point is ineffective.
The freezing test is an unscientific method and cannot be relied upon to determine the quality of the oil.
For example: if we mix a liquid vegetable oil that contains no saturated fatty acids with another oil that contains a high proportion of these acids (15%), then stir the mixture well and place it in the refrigerator, it will freeze and give the same consistency as olive oil. This is conclusive proof of the inaccuracy of the freezing test.
Therefore, when in doubt about the quality of the oil, one must resort to laboratory analysis or purchase from trusted sources, and not be swayed by propaganda claiming that frozen oil is authentic and unadulterated, while liquid oil is adulterated.
Among the unscientific propaganda methods is also relying on the color of olive oil as evidence of its quality.
But according to the specification, the color of olive oil ranges between:
This variation is due to differences in varieties, regions of cultivation, methods of cultivation, and harvest timing.
For example: oil extracted from the same tree at the beginning of the season tends toward green, while at the end of the season its color tends toward yellow.
One should not be swayed by home tests or unscientific propaganda such as the freezing test or the color of the oil; rather, one must rely on laboratory analyses and scientific standards to ensure obtaining authentic, high-quality olive oil.
