For most frying, keep the oil between 170–180°C / 340–355°F. This range quickly browns the outside of the food while cooking the inside without letting it absorb oil. If the temperature falls below this range, the food absorbs too much oil; if it rises above it, the outside may burn before the inside cooks. You can tell the temperature is right when small bubbles immediately form around the food as it enters the oil.
Why Use Two Frying Stages for French Fries?
For crisp french fries, first set the oil to 130–140°C / 265–285°F and partially cook the potatoes at this temperature. This softens the inside without adding color. In the second stage, raise the oil to 180–190°C / 355–375°F and fry the potatoes again briefly to crisp the outside. This two-stage method cooks the inside while browning the outside without letting the potatoes absorb too much oil.
Why is the temperature different for frying fish and chicken?
Fry delicate, thin foods such as fish at a slightly more moderate temperature, around 170–175°C / 340–345°F, because high heat can burn the outside before the inside cooks. Thicker pieces such as chicken are fried at 160–170°C / 320–340°F for a little longer so the internal temperature reaches 74°C / 165°F; check it with a thermometer in the thickest part, without touching the bone. Using a lower temperature and longer cooking time for thick pieces helps cook the inside without burning the exterior.
How can you check oil temperature without a thermometer?
If you do not have a thermometer, watch the bubbles rising from the end of a wooden spoon dipped in the oil to estimate its temperature. Fast, steady bubbling indicates around 170–180°C / 340–355°F, while slow, infrequent bubbles indicate a lower temperature. If a small piece of bread turns golden in 15–20 seconds, the oil is ready for frying. These methods are not as precise as a thermometer, but they are sufficient to tell when the temperature is much too low or too high.
Why is oil that is too hot a risk?
Oil starts to smoke above 200°C / 390°F. At this point, its composition is beginning to break down, and food can burn quickly on the outside while remaining raw inside. As soon as you see smoke, turn down the heat and wait for the oil to cool by a few °C / several °F. If you plan to reuse the oil for frying, remember that its smoke point drops a little with each use. Replace it when it darkens and starts to foam.
How does adding too much food at once affect the oil temperature?
When more food is added to the pan or pot than it can hold, the oil temperature drops suddenly and may take a few minutes to recover. During that time, the food continues to absorb oil and turns greasy instead of crisp. Fry food in several batches, covering only one-third of the pot's surface. If you add the next batch before the oil returns to the target temperature between batches, the same temperature drop happens again each time.
Does the type of oil change the frying temperature?
Refined vegetable oils such as sunflower and corn oil have high smoke points and can be safely heated to 180–190°C / 355–375°F. Olive oil has a lower smoke point, so it is preferred for medium-heat cooking rather than deep-frying. Dairy-based fats such as butter start to burn at around 150°C / 300°F, so they are not suitable for frying on their own. They are usually mixed with vegetable oil instead.