Many people believe that live fish represent freshness. However, scholars believe that the way the fish is killed is also crucial. Live fish may experience stress during transportation due to high density, which can affect their endocrine system and make the fish less palatable.

Fish undergo several stages after being taken out of water.

Fish undergo several stages after being taken out of water: pre-rigor mortis, rigor mortis, loss of freshness, invasion by microorganisms, and ultimately spoilage. Research on sea bass abroad has shown that if fish are kept in crowded conditions, they die more slowly, leading to lactic acid accumulation and a decrease in pH, accelerating rigor mortis and resulting in a softer, more brittle fillet.

The killing method is also important.

In addition to the impact of the breeding environment on fish quality, the killing method is also crucial. Xiao Xinyi explained that a study on carp slaughtering abroad compared the effects of asphyxiation, electric shock, carbon dioxide anesthesia, and mechanical shock on fish quality. The results showed that while electric shock is more efficient, it causes the fish to enter rigor mortis more quickly, resulting in a softer texture. Mechanical stunning preserves the fish’s moisture content and slows the onset of rigor mortis.

However, it requires more physical effort on the part of the butcher.

Live Stunning

If the fish is handled quickly after leaving the water, its quality is better maintained. For example, mechanical stunning can delay the onset of rigor mortis compared to electric stunning, making the fish less prone to breakage. Live Stunning, a common method used in Japanese restaurants, also preserves the fish’s freshness and sweetness by delaying the conversion of adenosine triphosphate (ATP) to inosine monophosphate (IMP).

Live Stunning disrupts the fish’s central nervous system, slowing the degradation of ATP, the energy-producing protein. This allows IMP, a key umami flavor released during this degradation process, to remain longer, preventing the umami flavor from quickly transforming into a rancid flavor. This helps the restaurant precisely capture the flavor of each fish.

For example, Japanese restaurants adjust shipping times based on the flavor profile of different seafood, whether it’s being eaten in the rigor mortis phase or after thawing, rather than blindly shipping live fish.

Domestic consumers are still relatively unfamiliar with this processing method, and as a result, “consumers are not accustomed to paying three or four times the price for something that looks the same.” Farmers who have tasted their own live-processed fish say there’s a difference, but few are truly willing to invest in this practice.

The biggest problem is that consumers can’t perceive the difference and are unwilling to pay the higher price, while processors perceive this process as a waste of time and a loss of profit. The live-processing method is worth promoting. Although the technical requirements are relatively high, the processed fish can be kept in ice water for nearly three days and still taste like freshly caught. Compared to the live fish in restaurant tanks, “it’s just alive, not truly fresh.”