Specific reasons:

Boiling lard is to remove water. Also add water to prevent the meat from burning when cooking. When lard is just boiled, there is no oil in the pot, which is easy to stick to the pot and form a black paste. Oil turns black when it is extracted. Adding water first can make lard rise slowly and not paste. After oil is produced, water turns into steam and evaporates.

In addition, if you add a little water when cooking lard, the boiled oil is not only white in color, but also fragrant in taste. Because the unique flavor of lard comes from a small amount of volatile aromatic substances contained in oil, such as glyceryl palmitate and glyceryl stearate.

These aromatic substances lose more at high temperature, and the fragrance will naturally not be rich after cooling. If you put lard into a pot and add a little water, when the oil temperature rises above 100℃, the water will boil, and the vaporized water will take away some heat.

The temperature in the oil pan will not rise sharply, the aromatic substances will escape less, and the oil residue is not easy to coke due to high temperature. The cooled lard is white in color and rich in flavor.