Colour of Tuna and Salmon in Sushi
You probably notice sushi tuna comes either in a vibrant red colour of a dull brown colour. Salmon is less obvious, but you can get a beautiful popping orange or a white-pinkish colour. Why is this?
When it is just caught and still very fresh, its color is a bright and deep red. This hue is so striking that it can almost seem unreal. The reason for this intense color is due to the oxygenated blood in the tuna.
However, as tuna ages, the color of its flesh can change from red to brown. This is because the oxygen storing myoglobin in the flesh breaks down and loses its oxygen, which causes the meat to become darker in color. While brown tuna is still safe to eat, it does not look as appetizing as fresh tuna. This difficulty remains when we freeze tuna, so we don't store tuna that often. In our kitchen, we marinate the brown tuna with flavour to mask the colour.
A freshly caught salmon also has a beautiful color, but it can vary depending on the type of salmon and its fat content. Salmon obtains its distinct pink colour from its diet containing the pigment astaxanthin. This colour is brought out as a popping orange hue in the trout “salmon” species due its lean meat.
Atlantic salmon, on the other hand, has a creamy pink color, especially in the females towards spawning season. The creamy hue is due to the presence of fat in the fish's flesh. Farmed salmon naturally has a high fat content, but during Autumn males tend to have better colours than females for this reason too.
Lastly, the pigmentation is also influenced by freshness and machine cut. A salmon meat that has been in contect with moisture (from a machine cut) or lost its freshness will become slightly dull, and the fine white fibres in the meat will be less distinct.