What you should know before mixing two frying oils

Trend tries

This habit, very recurrent in most homes, may not be so harmless. Not all kinds of oil tolerate heat the same or deteriorate at the same speed

On many occasions, we have been warned about how harmful it is to reuse the oil for frying. However, there are several recommendations to keep in mind when really determining its detriment. For example, olive oil is kept in optimal conditions for up to five uses. If we want to give it a second life, it must always be for frying or cooking, never for marinating or using raw; and it is also essential to filter the oil when it is cold after each use.

However, among all these suggestions, there is a habit that is repeated in many homes and that could also be harmful to our health: mixing the reused oil with new oil. Surely, most of us have ever used the remains of oil left in the bottle to reach the amount needed to fry a food, combining it with the remains of oil that we have already used on more than one occasion. A practice that many consider a saving of resources and a sustainable product where there are them, a title that is also very appropriate, but that clashes directly with the problems that can cause in our organism

Mix or not two types of oil

Did you know that oil, when degraded, produces polar compounds? We speak of a set of substances – such as monoglycerides, diglycerides or free fatty acids – which, as we have just seen, appear with the deterioration of this product after excessive heating and that directly affect the taste, aroma, and consistency of fats. Also, its content is characterized by the modification of triglycerides, the main components of fats. As dictated by Spanish regulations, included in the Order of January 26, 1989, in relation to the Quality Standard for Oils and Heated Fats, the presence of polar compounds in the oil must not exceed 25% under any circumstances. Abuse can trigger a large number of stomach upsets.

This obligation mainly affects “those natural and legal persons whose activity includes the use and handling of oils and edible fats heated to produce food products”; that is, catering companies , bars and restaurants or firms dedicated to the preparation of pre-cooked dishes, among others, according to the regulations set forth above. Unfortunately, this control does not affect the use that each individual makes of the oil in their own home.

A practice that, from now on, we should take very carefully, especially if we mix two types of oil. The reason? By having different degrees of saturation, their combination can accelerate the appearance of polar compounds before reaching that 25%. An effect that also happens when we combine new oil with used oil, since the latter would contaminate the other while accelerating degradation. In addition, each fatty material withstands a different maximum temperature, generating toxic substances that can spoil the food. For example, olive oil is more heat resistant than butter or sunflower oil. Under this premise, what other considerations should we consider during the frying?

– The temperature during frying must not exceed 200ÂșC. In fact, the higher, the faster the degeneration process. We also run the risk of forming other harmful compounds such as acrylamide, pre-oxides or acrolein, related to symptoms such as stomach irritation, ulcers, vomiting or the development of “genetic mutations and tumors”, in the case of acrylamide, according to the Spanish Consumer Agency (AECOSAN).

-As for the volume of oil that we should use, this should be proportional to the amount of food, since it is preferable that the ingredients are completely submerged.

-In addition, most experts advise using vegetable oils instead of animal fats, which have less stability.

The presence of polar compounds in the oil must not exceed, under any circumstances, 25%

-As is well known, before introducing food into the hot oil, they must be dry and thawed. And it is that the water they give off favors the breakdown of the oil.

-It is also not recommended to fry in a pan with a lid, as the condensation of steam generates water droplets that cause the same effect.


-A way to know if the oil is no longer suitable for human consumption is to look at its appearance. If it looks too dark, dense and viscous, it’s time to get rid of the oil. Stable foam formation is another indicator of product alteration. Of course, never throw it down the drain or the toilet, this could affect the purification of the waters. The best alternative is to take it to a clean point in your area. On the other hand, in relation to its conservation, different specialized organizations, such as the Organization of Consumers and Users, recommend keeping the oil away from light and heat so that it does not oxidize. In addition, contact with oxygen also accelerates its decomposition, hence we must store it in a completely closed container.

Leave a Reply

Your email address will not be published. Required fields are marked *

The trick to choose the best prawns