Formaldehyde is a colorless and odorless gas, which can't be perceived by human body at low concentration, but it will stimulate human eyes and nose at high concentration. Soluble in water and ethanol, its aqueous solution is commonly known as formalin, which has antiseptic and disinfectant effects. In the process of agricultural production, formaldehyde is occasionally used as bactericide and disinfectant. In the production of edible fungi, formaldehyde is occasionally used as an environmental disinfectant. Because it can also irritate users' eyes and nose, it is rarely used in recent years. Some consumers know that the formaldehyde content in mushrooms is very high, so will the formaldehyde in mushrooms be harmful to human body? What is the content of formaldehyde in edible fungi? This series of questions will be answered through the following experiments.
Experimental process
Teachers from the Laboratory of Beijing Agricultural Quality Standards and Testing Technology Research Center collected more than 100 samples from markets and edible fungi production bases in Beijing, Hebei and other places for formaldehyde detection and analysis experiments, including fresh Flammulina velutipes, Agrocybe aegerita, fresh mushrooms and fresh Pleurotus ostreatus. There are also dried Agrocybe aegerita, dried auricularia and dried mushrooms obtained from the market.
Firstly, the samples were pretreated by three different methods. The fresh samples in the edible fungi are homogenized into uniform samples by a homogenizer; Pulverizing some dried samples of edible fungi with a pulverizer; The other part of the dry sample is soaked in water and cooked (this operation imitates our usual habit of eating dried fungus and dried mushrooms) and then homogenized.
Then, 2g pretreated dry samples and fresh samples were added into the derivatization solution for derivatization and extraction. Finally, the derivative solution was detected by liquid chromatography, and the formaldehyde content was obtained by liquid chromatography analysis.
In order to explore whether the formaldehyde in mushrooms decreases or increases during storage, the teacher in the laboratory did the following experiments: after measuring the formaldehyde in mushrooms taken on the same day, put them in the refrigerator for refrigeration, and then measure the formaldehyde content in them every day.
experimental result
The experimental data show that the formaldehyde content of Agrocybe aegerita, Pleurotus ostreatus and Flammulina velutipes in fresh products is very low and almost undetectable. The formaldehyde content of different sizes of mushrooms in the base is also slightly different. The formaldehyde content of Lentinus edodes in the market is only about 10mg/kg, while that of Lentinus edodes is only about 40mg/kg. The highest content is medium-sized Lentinus edodes, with an average of 80mg/kg, and the highest content is 180mg/kg. This shows that formaldehyde is a metabolite in the production of Lentinus edodes and exists with Lentinus edodes.
A small amount of formaldehyde was also detected in dried auricularia auricula and dried mushrooms. After soaking and cooking, the formaldehyde content of Lentinus edodes decreased sharply, and its content was lower than 20mg/kg.
The formaldehyde content of Lentinus edodes stored at room temperature decreased sharply, and it could be below 10mg/kg after two days. In the case of cold storage, the formaldehyde content will also decrease, but the speed is slightly slower, and it can be reduced to below 10mg/kg after five days.
It can be seen from the experimental results that the formaldehyde content in fresh Flammulina velutipes, Pleurotus ostreatus and Agrocybe aegerita cannot be detected. However, a small amount of formaldehyde can be detected in dried auricularia auricula and Agrocybe aegerita, and only the content of formaldehyde in mushrooms is relatively high. As long as fresh mushrooms and dried mushrooms are washed, soaked and cooked, formaldehyde in them will also be eliminated.
Why do mushrooms contain formaldehyde?
Formaldehyde is an intermediate metabolite during the growth of Lentinus edodes. Literature research shows that the aroma substances produced during the growth of Lentinus edodes are actually the intermediate products of formaldehyde metabolism. Formaldehyde can also combine with protein and sugar in shiitake mushrooms to produce some fragrant substances, which are also popular substances. Especially in the process of drying mushrooms and drying them to make dried mushrooms, this substance will increase. That is to say, in the process of turning mushrooms into dried mushrooms, not only the flavor increases, but also the formaldehyde content increases. However, formaldehyde is a gas, which easily diffuses into the air. Moreover, it is soluble in water, which can be eliminated by soaking, boiling and boiling, and mushrooms will disappear during drying. Therefore, we can eat with confidence.