Adding salt late when stir-frying has always been recommended by nutritionists. They believe that adding salt just before the dish is done helps with health, so what are the specific benefits?
Helps with salt control
The timing of adding salt affects the texture and flavor of the dish. To achieve the same level of saltiness, adding salt later requires less salt than adding it early. The salt receptors on the human tongue interact with sodium ions on the surface of the food. If salt is added later, it doesn't penetrate deep into the food, but the tongue can still taste the saltiness. This allows for a reduction in salt usage for the same level of saltiness. If salt is added early, a significant amount of it penetrates the food, causing people to unknowingly consume more salt. Over the long term, this is detrimental to health.
Tenderizes meat, keeps vegetables crisp
As is well known, salt has a strong dehydrating effect. Fu Jinru pointed out that for meat dishes, adding salt when they are fully cooked or just before they are done results in meat that is tender and not tough. If salt is added too early, the proteins in the meat can easily coagulate, making the meat texture harder and causing it to shrink. When stir-frying vegetables, adding salt too early increases the osmotic pressure in the wok, causing the vegetables to lose water and appear "wilted" when cooked. Adding salt before the dish is done, however, keeps the vegetables crisp and delicious. For cold salads, adding salt too early will cause their juices to seep out, making them lose their crispness.
Reduces loss of nutrients
Researchers from Tongji University found that adding salt early during stir-frying causes a greater loss of vitamin C in vegetables compared to adding it late. This is because adding salt first causes the ingredients to release water, which carries away the vitamin C. In fact, the water带走不仅仅是维生素C，还有其他水溶性维生素， including folic acid, and vitamins B1 and B2. Inside the cells, they are protected to some extent, heat transfer is slower, and the loss is smaller. Once they are in the cooking liquid, they are directly exposed to high heat and lose the protection of other cellular components, leading to a significantly greater loss.
Reduces fat oxidation
Studies have shown that for meat products, salt is an oxidation promoter. Water-soluble chlorides exacerbate fat oxidation, and this process produces some substances harmful to the human body. When cooking meat, adding salt first leads to more severe fat oxidation. Therefore, it is best to add salt just before the dish is finished cooking.