Why does sushi taste so much better in Japan?

If you've ever dined at a high-end omakase sushi bar, you've likely noticed that much of the fish served is imported from Japan, particularly from the Toyosu Fish Market.

It's widely acknowledged among sushi chefs and culinary experts alike that Japanese fish is considered to be of exceptional quality. This leads to an intriguing question: does this fish genuinely taste better, and could this be the reason why sushi in Japan often seems to outshine its counterparts in the US and globally in terms of flavor?

Here's my perspective on this matter. Please bear in mind, this is simply my theory, based on the data I've gathered.

Fish Caught in Japan Have More Umami Than Those in the US

Fish in Japan often possess a more pronounced umami flavor compared to their counterparts caught in the Pacific Ocean near the West Coast of the US. For example, Halibut in Japan versus Pacific Halibut in California shows a marked difference in taste; the latter often tastes bland despite both being Halibut. This discrepancy could be attributed to the different environments, diets, and activity levels where these fish are raised.

A theory I've explored is that the varying umami levels between Japanese Hirame and its Pacific counterpart might be related to the ocean water's salinity. Ocean water in Japan tends to be saltier than the Pacific waters off California.

A map illustrating ocean salinity shows that the waters around Japan have higher salinity levels compared to those near the US West Coast.

The Relationship Between Ocean Salinity and Fish Taste

The saltiness of the water impacts fish taste due to the principle of equilibrium. Fish compensate for the salt in their environment by storing amino acids in their flesh, which are key to the umami flavor. More salt in the ocean means more amino acids in the fish, enhancing the savory taste. This principle partly explains why freshwater fish might taste blander due to lower salt content.

Thus, it's plausible that fish caught near Japan have more umami, contributing to the superior taste of sushi in Japan compared to other regions.

The Catch Method Matters

The method of catching fish significantly affects its quality. Stress during capture, such as a Tuna struggling, can raise its body temperature, compromising its quality. Fish caught using the single-line method undergo less stress than those caught using purse seining, which employs nets. High-quality Tuna from places like Oma, prized by top sushi restaurants in Japan, are often caught using the single-line technique.

The Importance of Post-Capture Handling

Post-capture handling is crucial for preserving fish quality. Ikejime, a method that minimizes stress and preserves quality by severing the fish's nerve and draining its blood, is common among fishermen who prioritize quality. While Ikejime is becoming more known globally, it's a meticulous process that adds to the cost. In Japan, Ikejime is mainly used for premium fish destined for high-end establishments.

Freezing and Thawing Techniques

Major sushi chains in Japan utilize fast-freezing technology to preserve fish quality. However, thawing is just as important as freezing. Japan has advanced commercial thawing machines that employ high-frequency and high-voltage methods, maintaining the fish's freshness and quality.

Scientific Knowledge Among Sushi Chefs

Japanese Sushi Chefs often have a deep understanding of the science behind their craft. Discussions on topics like thawing fast-frozen tuna according to the Maximum Ice Crystal Formation Zone are common among Japanese chefs but rare among their American counterparts. This scientific insight enables chefs to refine their techniques, such as knowing the optimal sequence for curing salmon, enhancing their culinary skills.

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