When the bought fat pork is unwilling to eat, it can be refined into lard by the following methods. The lard refined by this method is pure in color and taste, almost the same as vegetable oil.

First cut the fat into small pieces, add 5 grams of cold water to every 25 grams of fat, and boil it into liquid oil with slow fire (the oil yield can be above 8%). Dissolve caustic soda (sodium hydroxide) with water to form a solution (the ratio is 25g caustic soda and 15g cold water), add it to liquid lard at 5℃ and stir, and do flotation treatment. When the temperature continues to rise to about 7℃, add 25g cold water and stir constantly to make the oil reddish. At this time, the impurities in the oil will continue to sink, and it is better to sink completely.

The caustic soda used only plays the role of bleaching and precipitation, and is harmless to human body. This kind of oil can be stored for one year, and its oil quality remains unchanged.

note: boil lard to avoid fire. Lard is a neutral fat, which is easily hydrolyzed by acid, alkali, air, sunlight and related enzymes in human body to produce glycerol and fatty acids. Boiling lard with fire, the oil temperature can reach 23℃, which makes it chemically change and produce acrolein. Acrolein not only has a special odor, but also affects digestion after eating, causing gastrointestinal diseases; Stimulate oral cavity, esophagus, trachea and nasal mucosa, resulting in cough, dizziness, dyspnea and burning eyes, conjunctivitis, laryngitis, bronchitis, etc.

finally, don't eat the oil residue after boiling lard. The oil residue of fat pork after heating and refining contains carcinogens, which is harmful to health. Because of the high temperature in oil refining, the organic matter is decomposed by heat to form 3,4 benzopyrene. The longer the frying time, the higher the content of 3,4 benzopyrene. 3,4-benzopyrene is currently recognized as one of the three major carcinogens. Eating foods containing such carcinogens can cause cancer, especially increasing the incidence of esophageal cancer and gastric cancer. Therefore, lard residue is not edible.