Introduction: Dried foods are a staple in many households. However, controlling the water temperature during rehydration is a science in itself. If done correctly, it can restore the food to its original deliciousness; conversely, improper rehydration can turn expensive dried goods into waste, which is both a loss and a pity.
For this reason, our reporter interviewed Yu Renwen, the chief nutritionist for the VIP ward of the Beijing Military Region General Hospital, and Qu Hao, a master of Chinese culinary arts, to share their "secrets" for controlling water temperature when rehydrating dried foods.
Wood ear mushrooms and silver fungus should be rehydrated in cold water. Soaking wood ear mushrooms and silver fungus in hot water not only makes them difficult to fully rehydrate, but also results in a soft, sticky texture, and many of their nutrients are dissolved and lost. While rehydrating wood ear mushrooms in cold water takes longer, they are crisp and fresh to eat. Bean curd sheets should also be slowly rehydrated in cold water; boiling water will cause them to break, making them impossible to cook. When rehydrating, you can place a plate on top of the bean curd sheets to ensure they are completely submerged in water. This not only shortens the rehydration time but also ensures they rehydrate evenly for the best texture.
Dried shiitake mushrooms should be rehydrated in warm water. The special flavor of dried shiitake mushrooms comes from two components: mushroom essence and guanylic acid. Guanylic acid, in particular, has a umami intensity dozens of times greater than that of regular MSG.
When rehydrating dried shiitake mushrooms, it is best to use warm water at around 20-35°C. This allows the mushrooms to absorb water and soften more easily, and also enables the guanylic acid to fully break down, releasing its umami flavor. Additionally, do not soak them for too long; once the mushroom caps have fully softened, remove them and drain them immediately.
Kelp should be rehydrated by steaming. Kelp contains alginic acid and fucoidan, substances that are insoluble in water but have extremely strong water-absorbing and swelling properties. Once they absorb water, a viscous colloid forms on the surface of the kelp, preventing further water from penetrating, which makes it difficult to soak through completely. At the same time, most of the iodine in kelp is on the surface, and prolonged soaking will cause the iodine to leach out. Therefore, the best method is to steam it. Simply spread the kelp, steam it in a steamer for half an hour, then rinse it with water. It will be both tender and crisp. After rehydrating, you can add a little vinegar when eating to make it even softer and crisper.
Sea cucumbers should be rehydrated through alternating cold and hot water. First, soak the sea cucumbers in cold water for about 6 hours. Once softened, cut them open, remove the internal grit, and then rinse them in cold water for about another 2 hours. Finally, soak them in a weakly boiling alkaline solution for about 2 hours, repeating this process twice. After removing them, rinse them thoroughly with clean water and then "chill" them with ice cubes to better preserve the freshness of the meat. When rehydrating sea cucumbers, never use salt, as it will prevent them from rehydrating properly and can easily lead to spoilage.