When cooking, it is very important to master the heat of the oil. Use high heat when it's needed, and don't use low heat. Use low heat when it's needed, and don't use high heat. The temperature of the oil, whether too high or too low, also affects the aroma of the stir-fried dish. Especially for deep-fried dishes, if the oil temperature is too high, the fried food will be burnt on the outside and raw on the inside; if the oil temperature is too low, the batter or coating on the fried food is prone to falling off, making the dish not crispy.
For general stir-frying, not much oil is used, so you can start stir-frying as soon as you see smoke coming from the wok. For deep-frying, there is a lot of oil in the wok, and it's not practical to use a thermometer to measure the oil temperature, so you can only judge it by your senses.
After heating the oil in the wok, put the food to be fried into the oil. When it sinks to the bottom of the wok and then floats back to the surface, the oil temperature is about 160°C. This temperature is more suitable for making sugar-coated dishes, such as sugar-coated Chinese yam, sugar-coated sweet potato, and sugar-coated potato. At this time, the heat under the wok should be controlled to maintain the oil temperature.
After heating the oil, put the food into the oil. When it sinks to the middle of the oil and then floats to the surface, the oil temperature is about 170°C. This temperature is more suitable for making crispy chicken and crispy duck, which will be crispy on the outside and tender on the inside. During frying, the heat under the wok should also be controlled.
If the food to be fried does not sink when placed in the oil, the oil temperature is about 190°C. This is more suitable for frying various dishes with less moisture, such as dry-fried hairtail, dry-fried yellow croaker, and dry-fried pork tenderloin.
About Ten-Stage Oil Temperature
Recipes often describe the oil temperature as "several stages" hot. Since the ten-stage oil temperature scale is a method based on a chef's experience to estimate temperature, the estimation error often varies from person to person. Generally, an error of half a stage (±10-15°C) is allowed. Also, because the flash points of various oils are different, the same temperature for one oil is different for another. After cooking many times and gaining some experience, you can make a rough estimate. But don't treat cooking as an experiment. If you use a thermometer every time you cook, you will have too much hard work and lose the fun of cooking.