You’ve likely observed many times that a foam forms in the oil when frying. Let’s start by saying that this is a normal characteristic that should not alarm us, nor is it a symptom of low quality in the oil being used. In fact, our high-quality extra virgin olive oil from the Estepa Designation of Origin can also produce foam.
Nevertheless, the formation of this foam has an explanation and is caused by several factors, which we will explain below. These can be summarized as moisture, temperature, previous uses, and the oil’s own components.
Olive oil characteristics
Let’s begin with the last factor. Extra virgin olive oil is rich in fatty acids, some of which are free and react when subjected to high temperatures. This reaction causes their oxidation and decomposition, which results in the formation of foam. We can also add that higher temperatures lead to more foam, so not overheating the oil and preventing it from burning is also crucial for reducing its formation.
At excessively high temperatures, the oil degrades faster and produces more foam. However, we should add that extra virgin olive oil has a lower smoke point than other oils, giving it the advantage that we can reuse it more times while better maintaining its quality.
What are we cooking?
Besides the frying temperature, we must consider the moisture that the food being fried may contain. All foods, especially fresh ones, usually contain water, and when this water comes into contact with the hot oil, it evaporates and rises to the surface, forming the foam we are discussing. That is why it is good to pat very damp or even wet foods dry with kitchen paper; doing so will reduce the foam and also prevent spatters that can cause burns.
How many times did you use this oil for frying?
Finally, another key factor is the number of times you have previously used that oil. As we’ve mentioned, the oil degrades, and once you have used it extensively, you will observe a greater amount of foam due to the impurities it accumulates with each use. To help with this, it is beneficial to keep it reasonably clean by removing food scraps with a strainer, allowing you to use it more often. Containers for storing used oil are available on the market that incorporate a strainer beneath the lid to filter the oil after use. We recommend these because they improve its preservation and will help reduce the foam you encounter when frying.