Olive oil the “Liquid Gold”

Introduction

Olive oil is the most characteristic and perhaps the most important ingredient of the Mediterranean diet. According to Homer, olive oil is considered “liquid gold”, since it is not exclusively a component of the diet but can even be used as a medicine. Approximately 67% of olive oil worldwide comes from countries belonging to the European Union, with the main producers being Spain, Italy and Greece. In fact, Greece has the highest consumption of olive oil both in the European Union and in the world. It is estimated that approximately 12 kilograms of olive oil are consumed per person each year. Many scientific studies have been conducted to demonstrate the multiple health benefits of olive oil, with most confirming its contribution to both the prevention and management of many chronic diseases. In this way, its consumption is not only related to maintaining the health of individuals but also to reducing their overall mortality, ensuring longevity. It is estimated that even consuming olive oil in a low dose, less than 1 tablespoon per day, can reduce the risk of mortality from all causes by 9%, while consuming 2 or more tablespoons can reduce the risk by as much as 31%. A sufficient amount to consider that olive oil provides its beneficial properties to the body is 20 grams of raw olive oil per day, which corresponds to approximately 1 tablespoon.

Categories of olive oil

There are eight different categories of olive oil and olive pomace oil:

1. Extra (or extra) virgin olive oil
2. Virgin olive oil
3. Defective olive oil (or inferior or lampante virgin olive oil)
4. Refined olive oil
5. Olive oil consisting of refined & virgin olive oil
6. Olive pomace oil
7. Crude olive pomace oil
8. Refined olive pomace oil

Four of the eight categories above are available on the market: extra virgin olive oil, virgin olive oil, olive oil consisting of refined and virgin olive oil, and olive pomace oil.

Its classification is based on its physicochemical and organoleptic characteristics. The physicochemical characteristics refer to the acidity of the olive oil, the degree of oxidation and its content in fatty acids and polyesters, while its fruity taste and the absence of defects are the components of its organoleptic characteristics. The criteria for the quality of olive oil are the color, aroma, and fluidity of the olive oil, which are important factors for its classification.

Characteristics that degrade the taste and smell of olive oil and often its quality are:

• Mourga: The residue of the oil, which provides it with a characteristic smell and taste, without being harmful to health.
• Atrochado: Gives a characteristic smell and taste to olive oil that has resulted from olives that have been stacked in piles or stored in sub-ideal conditions.
• Mouldy: Gives a characteristic smell and taste to olive oil that has resulted from olives that have been infected by fungi due to their storage in a humid environment for a prolonged period of time.
• Tang: Gives a characteristic smell and taste to olive oil that has undergone oxidation.
• Vinaceous – vinegary, metallic or grease: It gives a characteristic smell and taste to the olive oil that resembles wine, vinegar, metal or oil respectively.
• The roasted/burnt: It gives a characteristic smell and taste to the olive oil that has undergone high heat treatment during the olive processing process.

Of the available olive oils, extra virgin olive oil is the best in quality olive oil, since it has a fruity taste and low acidity (lower than 1%), while virgin olive oil follows with a small degree of alteration of its characteristics and acidity lower than 2%. The olive oil that consists of refined and virgin olive oil and the pomace oil, although they do not belong to the virgin olive oils, are considered safe and suitable for consumption since they have been mixed with one of the mentioned virgin olive oils and have acquired an acidity level of up to 1%.

Health Benefits of Olive Oil

There are specific components contained in olive oil that provide its benefits. These include:

1. Unsaturated fatty acids: Monounsaturated fatty acids, mainly oleic acid (ω-9 fatty acid), and a good source of polyunsaturated fatty acids, mainly linoleic acid (ω-6 fatty acid)
2. Antioxidants: The main antioxidants in olive oil are oleocanthal, oleuropein, tyrosol and squalene. At the same time, olive oil contains a significant amount of vitamin E, mainly α-tocopherol, phenolic compounds, sterols, mainly β-sitosterol and carotenes. The above compounds, with the contribution of oleic acid, neutralize free radicals, ultimately reducing the oxidative stress of the body which is a result of their action.

Findings of scientific studies confirm the contribution of olive oil:

1. In the prevention and management of cardiovascular diseases: The presence of monounsaturated fatty acids is associated with a reduction in LDL cholesterol, an increase in HDL cholesterol and therefore an improvement in the lipid profile of individuals, reducing the risk of developing blood clots and atherosclerotic plaque resulting from the accumulation of fat in the vessels. The presence of antioxidant components of olive oil, mainly vitamin E, which prevents the oxidation of fat, also contributes to the prevention of plaque development. Studies support that a diet that includes olive oil can reduce the risk of cardiovascular diseases by at least 30% in high-risk individuals.
2. In reducing the occurrence of metabolic syndrome & Type 2 diabetes: Frequent consumption of olive oil helps, on the one hand, to maintain stable blood glucose levels, reducing the risk of developing type 2 diabetes, and on the other hand, to maintain blood pressure within normal limits. In this way, the risk of developing metabolic syndrome is reduced, which is characterized by the simultaneous presence of three of the following: hypertension, elevated glucose levels, elevated triglycerides and low HDL cholesterol.
3. Reducing the risk of developing specific types of cancer: The oleocanthal in olive oil targets and neutralizes specific cancer cells, while preserving healthy cells. In addition, the presence of other antioxidant components, mainly vitamin E and phenols, helps neutralize free radicals that cause structural changes in human DNA, constituting a key risk factor for carcinogenesis. The above may be a possible explanation for the low incidence of breast, colon, ovarian and prostate cancer in Mediterranean countries compared to Northern Europe.
4. In maintaining brain function and preventing the development of neurodegenerative disorders: Oleic acid enhances the function of neurons, resulting in an increase in the transmission of nerve impulses. In this way, cognitive functions such as memory, perception, thinking and speech are enhanced. Furthermore, since the central nervous system is particularly susceptible to oxidative stress, the presence of olive oil contributes positively to the reduction of oxidative damage and enhances the action of endogenous enzymes that function as antioxidants. In this way, the risk of developing diseases such as Alzheimer’s and Parkinson’s disease is reduced.
5. In maintaining the health of the intestinal microbiome and immune function: The health of the intestinal microflora is favored due to the metabolism of phenolic compounds, since they are not absorbed in the small intestine, but pass into the large intestine, constituting nutrients for its microbes, maintaining its proper functioning. Strengthening the intestinal barrier is directly related to strengthening the function of the immune system, since it is difficult for pathogenic microbes to enter. In addition, in the presence of olive oil, the likelihood of inflammation is reduced, due to its anti-inflammatory effect.

How to preserve olive oil

Given that the organoleptic and phytochemical characteristics of olive oil deteriorate over time, the shelf life of extra virgin olive oil is up to 18 months. Olive oil can be consumed beyond this period, but its taste and color will likely have significantly deteriorated. Storage conditions slow down or accelerate its oxidation, so proper preservation is necessary. We must take into account that:

1. In open containers, olive oil can be preserved for approximately three to six months. It is preferable to use small-capacity containers so that the contents are finished faster without being exposed to environmental factors that favor its oxidation.
2. It is preferable to use opaque and airtight stainless steel, tinplate or glass containers over plastic ones because olive oil interacts with its ingredients, resulting in its deterioration.
3. Avoid storing it in places with high light, temperature, humidity and the presence of undesirable factors such as mold and pesticides. Therefore, it is best not to place it on the kitchen counter in front of the window or in the cupboard under the tap. The correct storage temperature for olive oil is less than 18^o

Finally, through heat treatment, olive oil loses its antioxidant components and therefore its benefits. Therefore, there is a preference for its raw form over its cooked form as a component of the diet. It would be good to add it towards the end of cooking, so as to preserve the antioxidants it contains. If there is a need to fry, then the use of olive oil is preferred over other oils due to its heat resistance due to the presence of monounsaturated acids and vitamin E. The ideal cooking temperature for frying is 170-180^oC, while olive oil can withstand up to 215^oC. When olive oil reaches its “burning point”, the breakdown of its components is significantly increased and its reuse should be avoided.

Conclusion

In conclusion, olive oil is a key component of a balanced diet with multiple health benefits. Storing it in appropriate containers, at the right temperature away from undesirable factors, and using it correctly preserves its quality and benefits for a longer period of time. As a Mediterranean country, it is important to properly utilize this valuable food that has been generously given to us by nature and to properly incorporate it into our diet. However, it should not be overlooked that even the consumption of olive oil should be done in moderation. Of the recommended daily fat intake, which amounts to 25-35% of total energy, monounsaturated fatty acids are recommended to constitute 15-20% of this, given that the polyunsaturated fatty acids contained in fish and their oils as well as seeds are important for the prevention and management of diseases and ultimately the maintenance of health.