What are polyphenols?
Polyphenols are organic compounds that are the by-products of plant synthesis and are known as phytochemicals. They are highly regarded for their health promoting properties and can be found in fruits, vegetables, whole grains, nuts, seeds and legumes, beverages (coffee, tea and wine), red wine, chocolate, fats (olive oil) as well as spices and seasonings
There are 36 known phenolic compounds in olive oil. Among the types of polyphenols present in olive oil, several have been isolated: Hydroxytyrosol, Tyrosol, Oleacein, Oleocanthal, Oleuropein aglycone (closed aldehyde forms), Oleomisional, Ligustroside aglycone (closed aldehyde forms), Oleokoronal, Apigenin and Luteolin. Of these phenolic compounds some are unique to olive oil and only occur during the malaxation process (crushing olives to release juice). The two most widely researched for their health protective benefits are Oleocanthal and Oleacein.
The highest content of polyphenols is to be found in a specific type of olive oil: Extra Virgin Olive Oil (EVOO).
Why are polyphenols important?
Polyphenols are antioxidant compounds, which are important because they fighting free radicals in our body. These are oxidizing agents that cause the wear and tear of our cells and are produced as a result of our metabolism. Thus, they are responsible for aging and even serious diseases in some cases.
Our body generates some antioxidant enzymes that, unfortunately, are not enough. It is necessary to provide nutrients to complete their function. Among the external sources in which to find antioxidants, we have the phytochemical elements, which protect plants and animals that consume them. These are chemical substances that plants have and are responsible for protecting them from ultraviolet rays and, in general, against being damaged. Among these substances, we have polyphenols, which fight aging and have aroused special interest at the nutritional level in recent times. We find several types of polyphenols: flavonoids, phenolic acids, phenolic alcohols, stilbenes and lignans. Olive oil has one of the highest contents of polyphenols amongst the nutrients available to us.
Polyphenols have proven healthy and medical properties such as antioxidant and anti-inflammatory actions. In the case of olive oil, polyphenols protect the fatty acids in the oil against oxidation, thereby preventing the fats from oxidizing in the bloodstream and preventing the formation of obstructions in the blood vessels. Similarly, there is evidence of anticancer properties of polyphenols.
Phenolic compounds, in particular Oleocanthal and Oleacein are known for their anti-inflammatory and antioxidant properties. In vitro trials and an increasing number of human trials are studying the potential benefits of high phenolic olive oil in alleviating symptoms and potential therapeutic effect for Alzheimer’s, Rheumatoid Arthritis, Type II Diabetes, Leukemia and many cancers as well as other autoimmune and neurodegenerative diseases that are prevalent in today’s culture.
Presence of Oleocanthal is indicated by the peppery effect on the back of the throat often causing a cough reflex. Bitterness on the tongue is indicative of the presence of Oleacein. As olive oil is generally prized for its flavour and aromatic character, these characteristics of pepperiness and bitterness are often mistaken for a flaw in the olive oil. Nothing could be further from the truth.
How much polyphenol should we consume?
The European Union states it clearly in the EU Health Claim Labelling Regulation 432-2012: olive oil with polyphenols of 250 mg/kg (ppm) or more can claim:
“Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress. In order to bear the claim, information shall be given to the consumer that the beneficial effect is obtained with a daily intake of 20 g of olive oil”.
Most human research trials showing the effectiveness of EVOO on such illnesses as Alzheimer’s and Leukemia have used high phenolic EVOOs containing high levels of Oleocanthal and Oleacein. Research also indicates that high phenolic EVOO may be a very effective natural blood thinner like ibuprofen, but without the nasty side effects.
What factors influence the phenolic content of olive oil?
The polyphenol content of olive oil is significantly influenced by a number of natural and human factors. Here is a summary of some of the key ones:
- Olive variety: Certain olive varieties have a greater propensity to obtain significantly higher amounts of polyphenols than others. The Cornicabra variety typically has an extremely high content of polyphenols – in fact, one of the highest in the world. Other varieties contain far smaller amounts.
- Natural factors: soil condition, drainage, weather patterns (temperature, rain, drought, winds), bio-diversity in the grove (adds to soil richness and the olive´s nutrition) all impact phenolic content.
- Prioritize quality: EVOO from healthy olives grown using appropriate agricultural methods at optimum ripeness and freshly harvested have higher concentrations of polyphenols.
- Altitude: Olive cultivars located higher than 400m above sea level produce olive oil with a higher phenolic content.
- Irrigation: Olives produced on dry farmland or with low irrigation and rainfall produce EVOOs with a higher content of phenols. Olive cultivars with higher levels of irrigation or with high rainfall produce EVOOs with lower total polyphenol content. This is due to the fact that polyphenols are usually synthesized as a physiological response of the olive tree to situations of water stress to protect the fruit.
- Time of harvest: Normally the olives harvested at their optimum point of maturity during the veraison (moment during the ripening of the fruit in which it gradually changes colour from green to purple) produces more polyphenols, whereas those harvested when the olives are too ripe tend to have a lower concentration of polyphenols.
- Oil mill: The fruit should be carefully handled and transported from the field to the oil mill. It should arrive fresh and immediately after being picked. The cold extraction processing should be below 27ºC with minimal shaking of the olives produce an EVOO with more polyphenols. The objective is to minimize oxidation which is critical as most phenolic substances are volatile.
- Storage and packaging: When storing EVOO, it is important to avoiding oxygen, high temperatures and the direct sunlight. Storage tanks should be made of stainless steel, inert and temperature controlled. Packaging should be in opaque or dark bottles and containers to minimize the effect of light as it acts as a catalyst for oxidation. This will minimize the reduction of polyphenols and antioxidants.
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