When it comes to acetic acid or ethyl acetate, chemistry teachers often use grilled fish as an example to introduce an esterification reaction of acetic acid.
Generates ethyl acetate with an aromatic odor! No problem!
But. Is a fragrant braised fish fragrant because of ethyl acetate? Or is it because the fishy smell is removed?!
So here comes the problem!
The fishy smell is mainly related to the fish itself. We all know that the taste of fish is originally very delicious, and this umami mainly comes from the trimethylamine oxide contained in the fish body.
However, this trimethylamine oxide is very unstable and is particularly susceptible to being reduced to the fishy-smelling trimethylamine.
From the perspective of the physiological changes of fish, after the fish's life activities stop, the trimethylamine oxide in the body will continue to be reduced to trimethylamine, thus causing the fish to have a fishy smell. As the freshness of fish continues to decrease, the trimethylamine content in the body also increases, and the fishy smell of fish is very prominent. This also explains why when we kill fish, the fish will be very fishy.
The reason for the formation of fishy smell is not only its own factors, but also influenced by the environment. For example, freshwater fish generally grow in ponds, rivers, and lakes, and these places have more humus and are suitable for the growth of microorganisms. Bacteria containing earthy smell attach to plankton such as diatoms, cyanobacteria, and some aquatic plants. Freshwater fish ingest these substances through the food chain, and then enter the muscles, blood, and tissue cells, resulting in the earthy smell we smell.
Of course, improper storage is also another factor that causes fish to produce a fishy smell. When we do not store fish that have lost their activity, the fish will produce fat oxidation and amino acid degradation during the process of spoilage, thus increasing the fishy smell of fish. Common fishy substances mainly come from aldodes, in addition to alcohols, ketones and furans, such as aminovaleric acid, aminovaleraldehyde and hexahydropyridine in the mucus on the surface of fish, geosmin in water, 2-methyl isobornol, fish rot degradation products such as dimethylamine and trimethylamine.
When cooking fish, what are the effects of adding a small amount of wine, vinegar, and ginger?
Wine has the effect of coagulating proteins. Without protein decomposition, trimethylamine will not be formed. Adding vinegar can turn trimethylamine into an odorless salt; as for ginger, it is a synthesis of alcohols and ketones, both of which have a strong ability to remove fishy odors. Therefore, the main function of wine and vinegar is to remove the fishy smell of fish, not for esterification.
Reference: Xinhuanet
