Slick Extra Virgin» Interesting research results but don’t believe everything you read about olive oil

Olive fruit cultivar Arbequina was sampled every 15 days for 6 months from 6 trees at the perimeters of one conventional and one organic grove. With the exception of when the olives were totally black, the total polyphenols and the ability to act as antioxidants was the same or higher at all ripening stages in the conventionally grown olives.

Fernandez-Orozco et al. (2011) DPPH-scavenging capacity of chloroplastic pigments and phenolic compounds of olive fruits (cv Arbequina) during ripening. Journal of Food Composition and Analysis, 24, 858-864. doi:10.1016/j.jfca.2011.05.003

Comment: Not the result many would expect. This aside, why is it that whenever conventional farming is compared with organic farming, the less than optimal science comes out. While the focus of this paper was not to compare conventional olive production with organic production – they did draw conclusions based on such a comparison. So you can add this one to the very long list of poorly designed organic vs conventional experiments.

What makes organic v conventional comparisons difficult (and why they are rarely if ever done correctly) is that by definition you cannot have an organic panel of trees grown adjacently to a non-organic panel, as is done in most other agricultural trials. Maintaining organic status (as defined by certifying bodies) means that the experimental plots must be distanced from each other. Typically, the experimental plots are two separate groves owned and managed by different growers. Consequently the experimental trees usually experience different levels of water availability (either through different irrigation practices, being in different meso-climates, or by being planted in different soil types that drain differently). So in short, most of these experiments lack sufficient control over important aspects that can affect the things being measured and compared. Polyphenols in particular are highly dependent on tree water status – the more access to water, the lower the polyphenols. So control over plant water availability is crucial.

So what is the solution? For a start, researchers must realise that sampling from a single conventional and a single organic site equates to zero replication. Zero, zilch, none. The lack of replication in this type of comparison is the norm rather than the exception. I am continually frustrated that professional scientists who are called upon to review journal articles do not pick up on the fact that measuring a sample of something 3 or 4 times in the laboratory does not constitute real replication. If the researchers are concluding about farming systems, then the replication MUST be on the farm NOT in the laboratory. The researchers should select a number of sites for each treatment that are matched as closely as possible on the agronomic factors that can influence whatever they are interested in. A number of plots from within each site should also be selected and sampled from. This results in true replication that will allow variation within treatments to be compared with the observed differences between organic and conventional methods of production. Sure, research like this is expensive as it requires a lot of travel between sites and subsequent analysis. But unless it is done, the research says nothing at all about the effect of the farming system.


A new biochemical method to detect adulteration of extra virgin olive oil with soybean, corn or sunflower oil is described. It is based on its ability to detect two non-protein amino acids (ornithine and alloisoleucine) that are found in seed oil but not in olive oil. Up to 2% adulteration was detectable and the analysis took 15 minutes.

Sanchez-Hernandez et al. (2011) A capillary electrophoresis tandem mass spectrometry methodology the determination of non-protein amino acids in vegetable oils as novel markers for the detection of adulterations in olive oils. Journal of Chromatography A, 1218, 4944 4951. 10.1016/j.chroma.2011.01.045

Comment: The current method of using the plant sterol campesterol as a guide to possible adulteration with sunflower oil is archaic compared to this. Importantly, campesterol is naturally found in both sunflower and olive oil, so excessive amounts of campesterol are used to assess adulteration. However, what level is excessive is clearly arbitrary as campesterol levels depend on climatic conditions (usually higher in warmer climates), and importantly on variety. Varieties such as Barnea, Hojiblanca and Koroneiki (to name a few) naturally produce higher levels of this sterol. This new method is based on a go-no go method. If the olive oil contains these amino acids then the oil must have had seed oil added to it. This apparently definitive approach needs to be investigated further.


Yes this seems to be a series of unrelated facts, but they are show the economic importance of olive oil production even during the early Roman period. To put things into perspective – in 2010 Australia, produced 15,000 tonnes of olive oil, and one Roman Legion used as much oil as North Dakota (ok I made the last bit up- but I wouldn’t be far off US average consumption/3 x 670,000)

1) Baetica (Sth Spain) had over 1,000 presses and produced 19,000 tonnes of oil annually during the 400 years from 200BC-200AD. Rome’s hinterland produced 9,000 tonnes per annum, Tripolitania (NW Libya) 27,000 tonnes pa, Byzacena (Sth Tunisia) 36,000 tonnes pa.

2) Oileries in Byzacena had between 6 and 17 presses each.

3) Caesar circa 50BC taxed Tripolitania 900 tonnes of olive oil annually (presumably because he could!).

4) A Roman Legion of 6,000 men used 1400 amphorae (87 tonnes) of oil annually.

5) Over 260,000 amphorae were needed to transport oil produced from Baetica to Rome and other parts of the Roman empire.

6) Based on both estimated consumption and production, the major oil producing areas made in the vicinity of 170,000-260,000 tonnes annually.

Niaounakis (2011) Olive millwastewater in antiquity. Environmental effects and applications.Oxford Journal of Archaeology, 30(4), 411-425.

Comment: Well F me. Who would have guessed that they made that much freekin olive oil! But then again, what did people do before we had the internet? Rome might have given Tripoltania, Byzacena and Baetica education and aqueducts (a Monty Python Life of Brian reference there), but they sure gave them lots of olive oil in return).

On a serious note, I must apologise to the author. The purpose of the paper was to estimate the amount of olive waste-water produced in ancient times, and discuss how they dealt with it. I vowed when I started this blog that I would never report on waste-water. I keep true to my ideal. But for those who care. The ancients produced around 500 million litres of olive waste-water each year. What did they do with it? You’ll have to read the paper to find out. But you probably have guessed that their solution to the problem was mostly pretty ugly, but mixed in with a lot of delightfully quaint hippy stuff like blending it with ox urine and spraying it on vegetables, and usually just prior to picking and them preparing the family meal.

Source:  Slick Extra Virgin» Interesting research results  but don’t believe everything you read.

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