Animal-based foods generally contain fishy odor substances, with the smell of aquatic products being particularly prominent.
It intensifies as the freshness of the food decreases. These off-odor substances not only cause nausea but also pose health hazards after consumption. There are many methods to remove the fishy smell during cooking. Depending on the degree of off-flavor in the ingredients, a combination of measures can be used to achieve the goal of deodorization.
Neutralization to Remove Fishiness:
Animal-based food ingredients contain large amounts of nutrients such as proteins, amino acids, and lecithin. Due to the action of environmental and intrinsic bacteria, various fishy substances are produced, such as ammonia, trimethylamine, methyl mercaptan, hydrogen sulfide, indole, and nitrogen-containing heterocyclic compounds. The above-mentioned fishy and odorous substances are all alkaline compounds (pH greater than 7.25). During cooking, adding an appropriate amount of vinegar to neutralize them can form acetates, which greatly reduces the fishy and odorous smell. In addition, tomato sauce contains organic acids such as citric acid and malic acid, which also have a neutralizing and deodorizing effect. Of course, cooking fish and meat directly with tomatoes also has a deodorizing effect.
Alcohol-Based Deodorization:
For some fishy substances with low boiling points and non-alkaline properties that cannot be removed by neutralization, the solubility and volatility of alcohol (ethanol) can be utilized. The aldehydes, ketones, and sulfur-containing compounds in fish and meat are first dissolved by the alcohol, and then volatilized and removed together upon heating. At the same time, ethanol can also react with aldehydes in the ingredients to form aromatic substances—acetals. It can also combine with organic acids to form esters. The combined effect of these two reactions can deodorize the dish and enhance its aroma. Therefore, to achieve a fresh and savory flavor in fish and meat, cooking wine and vinegar are indispensable.
Spice-Based Deodorization:
China boasts a wide variety of spices, which can be selected according to the specific situation. For example, scallions contain volatile oils and allicin, ginger contains gingerol, gingerene, and shogaol. Sichuan pepper and black pepper contain sanshools. Star anise contains anethole and anisole, and cinnamon contains volatile oils and organic acids. The aforementioned substances can cause oxidation, acetalization, or esterification reactions with fishy components such as aldehydes and ketones, reducing the off-flavor while enhancing the aroma. The deodorizing and flavor-enhancing effect is more pronounced when used in animal-based ingredients with a strong gamey or fishy smell.
Heat-Based Deodorization:
Fishy substances with low boiling points, such as methyl mercaptan and ethyl mercaptan, can be removed by heating. Some fishy substances with higher boiling points can also be removed by prolonged heating methods such as stewing, braising, roasting, or grilling, or by allowing them to volatilize in hot oil. Most fishy substances are water-soluble. During cooking, methods like blanching or scalding in boiling water can be used first to remove water-soluble fishy substances such as urea, amines, and low-molecular-weight acids before proceeding with the main cooking process.