During the Spring Festival, to enhance the flavor of dishes, dried shiitake mushrooms are a common ingredient in family banquets. However, have you ever wondered why dried shiitake mushrooms release their flavor more easily than fresh ones when cooking?
Generally, most foods taste better when they are fresh. But shiitake mushrooms might be one of the few exceptions. If we disregard texture and mouthfeel and consider only flavor, dried shiitake mushrooms are more fragrant than fresh ones.
The "fragrance" mentioned here is, in scientific terms, actually "umami." The substances in food that produce umami are mainly three types: glutamates, inosinates, and guanylates. Most foods contain precursors to these umami substances, which are released under appropriate conditions, allowing us to taste "umami." Generally, foods like kelp, beans, potatoes, meat, and fish contain relatively high levels of glutamates, while beef, chicken, fish and shrimp, and pork contain a lot of inosinates. Mushrooms, especially shiitake mushrooms, are rich in guanylates. These foods therefore naturally possess a considerable amount of "umami" flavor.
In fresh foods, these umami substances may exist in other forms and only produce umami when released. Some processing methods help with this release. For example, stir-frying, boiling, grinding into soy milk, or curdling tofu from raw soybeans does not help release the glutamates within them. However, if the soybeans are fermented into soy sauce or fermented black beans, their glutamate content can be greatly increased.
The umami substance in shiitake mushrooms is mainly guanylate, which is converted from other substances in the mushroom. During the drying process, this conversion is greatly increased, so the guanylate content in dried shiitake mushrooms is much higher than when they are fresh. A similar process occurs with dried fish, which, without any seasoning, has a much more intense umami flavor than fresh fish.
What's more interesting is that when glutamates are mixed with inosinates or guanylates, the resulting umami is much stronger. This is why cooking shiitake mushrooms with chicken produces a very savory flavor, while stewing them with green vegetables does not.
In Southern China, there is a tradition of "slow-cooking soups." People often cook old hens with ingredients like shiitake mushrooms and wood ear mushrooms for a long time to obtain a very rich broth. The meat and bones of an old hen contain more umami substances than those of a young chicken, and the long cooking time helps to release them. Ingredients like shiitake mushrooms and wood ear mushrooms also contain umami substances. When various umami substances are released and work together, they create an extremely rich savory flavor.
However, it is important to know that these substances that produce umami have little to do with nutrition. A soup that has been "slow-cooked" to be very savory does not necessarily mean it is more "nutritious." Nutrition depends on what is consumed, regardless of whether it is in the soup, in the meat, or in the vegetables.