Nekasei Fish Aging Japanese Technique

Edomae sushi tradition, Tokyo — refined through 20th century sushi master practice

Nekasei (寝かせ, 'letting rest/age') is the Japanese practice of controlled fish aging, now emerging from sushi counter tradition into broader practice. Unlike Western wet aging, Japanese nekasei uses precise refrigeration (0-2°C) with the fish wrapped in paper or placed on wooden boards to wick moisture, allowing enzymatic activity to convert proteins to amino acids (glutamate, inosine monophosphate) while controlling bacterial activity. Aged fish develops deeper umami, softer but not mushy texture, and concentrated flavor. Each species has optimal aging windows: lean white fish (hirame, tai) 3-7 days; fatty fish (buri, saba) 1-3 days; tuna (maguro) 3-10 days depending on portion.

Deepened umami, silkier texture, complex amino acid sweetness amplified over fresh fish