Recent investigations have shown that frying is beneficial to the organism, particularly from the physiological point of view. Because of this, it has extended to areas where formerly it was not as popular. Whether the food fried is digested easily or lies heavily on the stomach depends to a great extent on the type of oil used, the temperature of the oil and the manner in which the food was fried. Studies undertaken on healthy subjects and patients with gastroduodenal problems (gastritis, ulcer, liver and biliary complaints) have shown that there is no relationship between food fried in olive oil and these illnesses.

The alteration undergone by vegetable oils when heated for frying is quicker and more atty acids (seed oils), and the higher the initial acidity of the oil (it is more stable if it has a high content of natural antioxidants – vitamin E). This alteration also varies according to temperature and length of time heated, number of times used, manner of frying (in continuous frying it changes less), and the type of food being fried (frying fish, especially oily fish, increases the polyunsaturated acid content of the oil, facilitating its decomposition).

Olive oil is ideal for frying. In proper temperature conditions, without over-heating, it undergoes no substantial structural change and keeps its nutritional value better than other oils, not only because of the antioxidants but also due to its high levels of oleic acid. Its high smoking point (210ºC) is substantially higher than the ideal temperature for frying food (180ºC). Those fats with lower critical points, such as corn and butter, break down at this temperature and form toxic products.

Another advantage of using olive oil for frying is that it forms a crust on the surface of the food that impedes the penetration of oil and improves its flavour. Food fried in olive oil has a lower fat content than food fried in other oils, making olive oil more suitable for weight control. Olive oil, therefore, is the most suitable, the lightest and the tastiest medium for frying.

It goes further than other oils, and not only can it be re-used more often than others, it also increases in volume when reheated, so less is required for cooking and frying.

The digestibility of heated olive oil does not change even when re-used for frying several times.

Olive oil should not be mixed with other fats or vegetable oils and should not generally be used more than four or five times.

The oil used for frying should always be hot; if it is cold the food will soak up the oil.

There should always be plenty of oil in the pan when deep frying. If only a small amount is used, not only will it burn more easily but the food being fried will be undercooked on top and overcooked on the bottom.

When heated, olive oil is the most stable fat, which means it stands up well to high frying temperatures. Its high smoking point (210º C) is well above the ideal temperature for frying food (180º C). The digestibility of olive oil is not affected when it is heated, even when it is re-used several times for frying.