Introduction

Virgin olive oil is one of the fundamental foods of the Mediterranean Diet, often referred to as our liquid gold.

Olive oil is the juice of the olive, and its various types result from the different procedures and refining processes it undergoes. It has key characteristics that define it: it can be consumed raw, used for cooking, and withstands high temperatures without breaking down. Moreover, it is the only product that may legally be called “oil”; other products on the market with this name are actually seed-based vegetable fats.

Olive Oil

Extraction Process

To obtain the oil, olives are crushed with rollers or millstones to produce a paste, which is then mechanically pressed to extract the oil. This process can be done either cold or hot. Although hot extraction yields more oil, it requires further refining. Up to 20% more oil can be extracted from the remaining cake using authorised solvents, which are later evaporated through heat.

The refining process is carried out to remove impurities formed during extraction that may impart undesirable flavours to the oil. These processes also reduce the acidity level and mellow the flavour.

Acidity and Purity

There are two parameters that define the quality of olive oils: acidity and purity.

Acidity refers to the amount of free fatty acids in the oil. It is a chemical parameter that, in olive oil, is not related to colour, aroma, or taste – meaning there are virgin olive oils with very low acidity yet strong flavour.

Purity is a term used to qualify oils with a mild taste or to identify high-quality virgin oils (extra virgin).

Virgin olive oils are obtained from olives through mechanical processes at ambient temperature. These oils are classified at the mill based on their free acidity, which reflects the quality of production and their taste and aroma characteristics.

Types of Olive Oil

Extra Virgin Olive Oil
This is the highest quality virgin olive oil, without any defects in flavour or aroma. Its fruitiness, coming from fresh, healthy olives (either green or ripe), can vary in intensity depending on the olive variety and the oil’s production method. Its free acidity must not exceed 1%. Its colour may range within yellow-green shades. The label may include the term “natural” and it may be designated with a denomination of origin if it meets certain regional quality criteria.

Virgin Olive Oil

Compared to extra virgin olive oil, this oil has minor organoleptic defects. Its free acidity must not exceed 2%.

Olive Oil

This is a blend of refined olive oil (from the refining of lampante virgin olive oil) and edible virgin olive oil in varying proportions. The virgin olive oil provides the blend with its sensory characteristics and antioxidants that are removed during refining. The free acidity of olive oil must not exceed 1.5%.

Olive Pomace Oil

This is a blend of refined olive pomace oil and edible virgin olive oil in varying proportions. As with standard olive oil, its free acidity must not exceed 1.5%.

From the olive paste left over after producing virgin olive oils, crude pomace oil is obtained using solvent extraction. This oil must be refined before it can be used for consumption.

Identifying Oil by Colour

Not all olive oils are the same, and they can be distinguished by their colour.

Golden-yellow oils tend to be mild and sweet, generally harvested later. Yellow-green oils are usually fruitier and often slightly bitter, as they come from olives that have not fully ripened.

Oil by Region of Origin

Andalusian oils, mostly from picual, picudo and hojiblanca olives, are fruity, smell of freshly cut grass, slightly bitter and somewhat peppery, and show great resistance to rancidity. They are perfect for cooking fish, stir-fries, stews, marinades and dishes with garlic.

Bajo Aragón oils, from the “empeltre” variety, are sweet, viscous and have a very refined palate, though they are prone to rancidity. They are ideal for making mayonnaise or for use in delicate modern cuisine dishes.

Catalan oils, from the arbequina variety, smell of green apples, almonds and nuts. They are ideal for dressing salads or the classic tomato bread.

Toledo oils, made from cornicabra olives, are slightly bitter and peppery.

Olive Oil in Cooking

One thing is certain: the ideal use is raw, to enjoy all its benefits. However, as mentioned earlier, it is a fat that withstands cooking perfectly without losing its qualities — provided certain parameters are respected.

During frying, food quickly changes its physical, chemical and sensory characteristics, often affecting its nutritional quality. This is why it is important to understand best practices for frying food.

Thanks to its high oleic acid content and low polyunsaturated fat content, olive oil is far more stable and degrades less than seed oils (such as soybean, sunflower, corn, etc.).

When oils are heated above 180°C, thermal breakdown may occur, leading to degradation.

There is a difference between frying foods with no intrinsic fat content – like potatoes or peppers – where the final fat content comes solely from the frying oil, and frying fatty foods like meat or fish. In the latter, once the water has evaporated, oil begins to penetrate the food. Typically, the amount of fat absorbed from the frying oil equals the fat released from the food into the oil.

When frying, oil should be heated gradually. Frozen foods should not be fried by sharply increasing the temperature.

Discontinuous frying processes alter oils more than continuous ones. Oil degradation depends on how often it is reused and on the food being fried.

To avoid accelerating oil degradation, choose oils with low unsaturation, use the lowest possible frying temperature, limit the number of reuses, and avoid prolonged frying at high temperatures without food.

Nutritional Value of Olive Oil

It is a fat that provides 9 kcal per gram.

The best oils are those obtained by cold pressing. They are rich in vitamin E, beta-carotene (provitamin A), antioxidants and phytosterols.

As a monounsaturated fat, olive oil lowers LDL cholesterol and increases HDL cholesterol, thus supporting cardiovascular health. Additionally, studies suggest that virgin olive oil has anticoagulant properties that help prevent blood clots.

A good olive oil is not only delicious, it is also full of benefits — so think of your health and use olive oil as your main cooking fat.