Deep frying is perhaps best explained as a process composed of several smaller chemical processes; these processes aren’t difficult to grasp, though. Misconceptions state that the process makes food oilier; meanwhile, deep frying shouldn’t make food oily, since it is, in fact, a type of dry cooking.
The reason for this will become clearer soon enough.
In summary, deep frying is neither a difficult nor a very time-consuming exercise. Food is placed in a vessel where oil has been heated to between 325-400ºF.
The purpose of this is (1) to give food that beloved, crisp exterior, and (2) to cook your food.
Different food types take different lengths of time to deep fry. With that said, one shouldn’t let the food fry for too long, as this is what makes it turn greasy
Deep frying in more depth
To understand this process, we’ll explain in details how it works. We can identify four phases within the process.
First Phase: Initial heating
The oil is heated to between 325-400ºF. Food is then placed in the oil, at which point the food begins deep frying. This sudden heat increase cooks the food’s surface and seals the moisture of the as-yet uncooked food.
Second Phase: Surface boiling
The moisture that is inside the food heats up and becomes a vaporous form of water. The vapor then cooks the food – much like boiling would cook an egg or a potato.
Tiny bubbles start to appear where the food’s surface meets the oil, forming a gas barrier. That barrier keeps the oil out, which keeps the food dry throughout the deep-frying process.
These bubbles are in fact water: the water inside the food becomes gas when the food touches the hot oil, exiting before the heat seals the remaining water vapor inside the raw food.
Oil and water do not mix, meaning practically no oil reaches the food’s surface at this point. The bubbles shield the food so that no oil penetrates inside the food.
Third Phase: Decreasing heat transfer
At this point, the transfer of water from the food begins to decrease. The last dregs of liquid become steam inside the food.
Fourth Phase: Bubble end point
The bubbles vanish from the food’s surface; at this stage, there is no boiling or deep frying of the food’s external layer. The food should be removed to prevent oil entering the deep-fried meal (the bubbles no longer protect the surface).
The right temperature
The temperature of the oil must be between 325-400ºF for the first stage of frying to take place. If it isn’t, the food will not cook; the surface won’t seal and oil will be allowed to penetrate it, making it greasy and unpleasant.
At the same time, don’t leave the food inside longer than it takes to deep fry fully. The bubble shield can no longer ward off the oil; thus you will have the same outcome.
The dry crust, the main reason people love deep-fried food, comes from a balance between these two factors.
Which oil should you use?
When choosing an oil to deep fry with, find out which oils give the best outcome, and which are the unhealthiest. The more saturated fats there are, the better.
Coconut oil has proven to be the best for deep frying. Research shows that this oil can be reused even after it is cooked for a long period.
Other oils that work in deep frying are those made from olives, peanuts, palm and avocado. Animal fat works and is acceptable.
Do not use vegetable oil (soybean, corn, canola, grapeseed, sunflower) as these tend to produce compounds that are deleterious to your health.
How to deep fry?
We have already explained why it is crucial to make sure the oil temperature is high enough. In this case, the food surface seals before oil can enter it; the food’s steam then cooks the food’s insides.
With raw food, you may risk burning the food’s surface before the food inside has been cooked. This can be avoided by warming the food up slightly, letting the inside heat up.
To help seal the food’s surface, you may also coat the food. Bread crumbs work well in this case.