What's the matter with cooking oil foam

Foam of edible oil is usually caused by high-temperature oxidation, water residue or repeated use of oil. Foam may be caused by excessive oil impurities, high oil temperature, food residue mixing, oil rancidity, incomplete cleaning of pots and tools and other factors.

1. Excessive oil impurities

Unrefined edible oil contains natural impurities such as phospholipids and free fatty acids, which will reduce the surface tension and form foam when heated. Semi refined oils such as peanut oil and rapeseed oil are more prone to this phenomenon. Before use, the new oil can be left to settle or first grade refined oil can be selected.

2. The oil temperature is too high

When the oil temperature exceeds the smoke point, the oxidation reaction will be accelerated, and polymers and polar substances will be generated, leading to the increase of foam. The smoke point of different oils varies greatly, with soybean oil at around 230 degrees and sunflower seed oil at around 225 degrees. It is recommended to use an oil temperature gauge to control cooking at medium heat.

3. When food residues are mixed with

fried foods with high starch or protein content, the peeled flour coat and meat crumbs will react with oil in Maillard, producing gelatinous substances to promote the formation of foam. After each use, the residue should be filtered to avoid mixing different ingredients for frying.

4. Oil rancidity

Edible oil that has been unsealed for more than 3 months may undergo hydrolytic rancidity. When the content of free fatty acid increases to more than 1%, heating will produce continuous foam. It can be judged by smelling whether there is a halal smell. It is recommended to store in a cool and dark place and use within the shelf life.

5. The pan is not thoroughly cleaned

The residual detergent or food carbide at the bottom of the pan will change the oil surface activity, especially the stainless steel pan is more prone to foam splashing. Before cooking, the cookware should be thoroughly wiped dry to avoid contact between cleaning agents and oils.

When using edible oil in daily life, it is recommended to control the single use amount and avoid prolonged high temperature heating. Frying oil should not be used more than 3 times. When storing, choose a sealed container away from light and keep away from heat sources such as stoves. If the oil color darkens, viscosity increases, or odor appears, it should be immediately stopped from use. For oils with severe foaming, a few slices of ginger or scallions can be added to help defoam. However, oils with repeated foaming may pose a safety hazard, and it is recommended to replace them with new oils.