What happens to oil when it is used for cooking? There are many circumstances in which oil can evaporate.
Many people wonder if oil is used up by the ingredients or if it evaporates. However, as I’ll show later, cooking oil doesn’t evaporate when cooking.
Technically, oil breaks down and “cooks off”, but this isn’t actual evaporation.
Confused? Don’t be.
I’m about to answer the question, “Does oil evaporate?” fully and clearly.
Does oil evaporate?
Some oils can evaporate. These are called “volatile” oils, and they can evaporate if they are exposed to the air. Other oils, however, are unable to evaporate. These latter oils are called “fixed oils”.
Water evaporation vs. oil evaporation
There are two things to be aware of when heating something: boiling point and smoke point. The smoke point is not as high as the boiling point in vegetable and cooking oils.
Oil breaks down into constituent molecules at the smoke point, and some of those molecules get converted into gas. At this temperature, smoke becomes visible, and the oil starts to vaporize.
Notably, some types of oil particles will vaporize. In contrast, others don’t, so there will always be a residue left of heavy particles behind.
Evaporation occurs when liquids arrive at their boiling point. At the boiling point temperature, whole molecules of the liquid turn to gas without breaking down.
With water, for instance, heat cannot break down water molecules before those molecules get enough energy to turn to water vapor. So, evaporation takes place because water turns to vapor at 212°F.
Water doesn’t have a smoke point. It only has a boiling point. In contrast, oils have both a smoke point and a boiling point.
When heated, oils that reach their boiling point before their smoke point are called “volatile”. These oils can evaporate.
On the other hand, the other type of oils, called “fixed”, reach their smoke point before they reach their boiling point. This means that fixed oils can’t evaporate. Instead, they just smoke and partly vaporize.
The distinction between vaporization and evaporation is that the former will always leave a residue.
Fixed vs. volatile oils
Fixed oils, aka are sometimes called “carrier” oils. Technically speaking, fixed oils are genuine oils.
Volatile oils, aka “essential” or “ethereal” oils. Technically speaking, volatile oils are not oils.
Volatile oils come from barks, roots, and tree petals. Perfumes use volatile oils because of their aromatic properties.
Volatile oils are sometimes called essential oils, but not because they are important for the body. It’s because they have the essence or scent of the flower from which they came.
Volatile oils are aromatic compounds that can be used in aromatherapy for relaxation and pleasure. However, they can cause allergic reactions and skin irritations.
These are the oils that come from kernels, nuts, or seeds. Oils that come from these sources are also called “vegetable oils”.
Another type of fixed oil comes from animals. Animal oils are now known to be healthier than vegetable oils, being primarily saturated oil and containing fewer toxic and carcinogenic (cancer-causing) agents.
Vegetable oils are industrially bleached, refined, and flavored. In contrast, animal oils undergo far less processing.
Whether vegetable or animal, fixed oils are the main oils used for cooking.
Can room temperature evaporate oil?
The clue is that cooking oil smells strongest when first exposed to the air. The reason is that the oil is losing some of its volatile molecules (which happen to be the aromatic, best-tasting ones) to the air.
So, yes, left at room temperature, part of the oil rises into the air, but this is not evaporation. Only the scent molecules in oil rise at room temperature, creating a noticeable smell.
Oil is composed of many different substances, and each substance vaporizes differently under particular conditions. The smell of oil when its container is opened indicates that the oil is vaporizing.
Why is there a residue from oil when cooking?
People often believe that oil evaporates at high temperatures, leaving behind a residue.
First of all, oil does not evaporate. It reaches its smoke point before it gets the chance to evaporate.
Instead of evaporating, oil is usually soaked up by the food it cooks. Any oil which isn’t absorbed is left behind as residue.
Specific oil molecules also vaporize when oil is used in frying. This part of the oil causes smoke and leaves behind a residue that will burn if the heat isn’t turned down.
The same is true of oil when heated in a saucepan on high heat. First, it smokes, then starts to burn, and finally, it will leave a thick, dark, smelly residue.
Oil evaporation does not occur in reality. The fake effect of evaporation is simply a result of cooking for these three reasons.
- Oil breaks down earlier than its boiling point.
- Oil droplets escape into the air when oil is fried.
- Smoke from oil is mistaken for oil vapor due to evaporation.
What can make oil evaporate?
Energy is the main reason not just oil, but all liquids evaporate. For example, think about molecules in any liquid.
The rate at which a molecule rushes about in a liquid determines its probability of becoming vapor. The more energy supplied to the liquid in the form of heat, the more probable it is that any molecule will leave the liquid and enter its gaseous state.
The weight of the liquid’s molecules (they all weigh exactly the same) plays a significant role in whether a liquid will quickly evaporate or not. Fixed oils are made up of giant, extremely heavy molecules that don’t evaporate.
Frequently Asked Questions About Does Oil Evaporate
Where does oil disappear to when during cooking?
Oil either breaks down and vaporizes, or it is absorbed by the ingredients in the food. It doesn’t evaporate because cooking oils are fixed oils, and (unlike volatile oils) they can’t evaporate.
What’s a “smoke point”?
“Smoke point” is when oil begins separating into unsaturated fats. At this temperature, the oil starts smoking. Vaporized unsaturated fats are flammable, so at this point, the oil more easily catches fire.
Does oil dry out on its own?
Volatile oils do, but non-volatile ones don’t. However, oils can react with oxygen if they are out in the open for too long, causing the oils to thicken and appear to lose volume.
Afterword: Does oil evaporate?
Evaporation happens when entire molecules in a liquid change into their gaseous form. Molecules in fixed oils break down before they are energetic enough to leave the oil, so fixed oils cannot evaporate.
On the other hand, molecules in volatile oils change into their gaseous form whole and unbroken even at room temperature.