All about sea urchin

A delicacy in many cultures, knowledge is key when it comes to sourcing, storing and preparing sea urchin. Red Claw Seafoods’ Thuy Pinson gives us a lesson on uni.

Behind the spines

Sea urchins are an ancient organism without organs such as a heart or blood vessels. They consist of a mouth, gut tube, a primitive nervous system and five delicate tongues of gonads encased in a spiky hard shell, which is the consumable part commonly known as sea urchin roe or uni. The gonads perform dual reproductive and nutrient storage functions.

Diversity of species

There are three species of sea urchins commercially harvested in Australia. Their common names can be confusing as the colour descriptions do not correspond with the apparent colour of the sea urchin.

Centrostephanus rodgersii is known as purple sea urchin or the long spine sea urchin. It comprises the majority of the commercial catch in Australia. These urchins are found off the coasts of New South Wales, eastern Victoria, the east coast of Tasmania and the eastern Bass Strait islands. These spawn in winter from late June/July to August and are best in autumn.

Heliocidaris tuberculata is know as the red sea urchin. These can be harvested from southern Queensland to the South Coast of New South Wales. They spawn from February to October depending upon their location. Generally, they are best in late spring to early summer

Heliocidaris erythrogramma is known as the green, white or purple sea urchin. These are found in southern Australia from sub-tropical New South Wales to Shark Bay in Western Australia and also Tasmania. They spawn in the summer and are best consumed in spring.

Tripneustes gratilla are known as lamington sea urchins. These sea urchins naturally occur in both Japan and Australia. They are no longer commercially harvested from the wild due to their low numbers; however they will be farmed and commercially available in the near future. Farming this urchin will produce superb uni throughout the year.

Flavour profile

A sea urchin that has just been taken from the sea, cracked open and washed in the ocean tastes sweet yet creamy with a burst of umami. The texture is soft and pillowy, melting in your mouth like butter.

The flavour and condition of uni is influenced by a number of variables such as the species of urchin harvested; the type, quantity and quality of food consumed; the stage of the reproductive cycle; the water temperature and the amount of daylight and weather.

Sourcing

If you are not able forage for sea urchins yourself, they should be bought live from tanks. Live sea urchins should be held in suitably maintained holding tanks in which they will retain their vitality and quality.

Uni is at its best when the urchins are in their peak nutrient-rich stage. This is the stage before the sea urchins are getting ready to spawn.

If the uni is weepy and milky, the urchins are in their reproductive stage and texture will be disappointing.

Alternatively, if the uni is skinny or empty, the urchins have just spawned and were not suitable for harvesting.

Storage

Sea urchins should be processed within 24 hours of obtaining them live. It is not recommended to store sea urchins out of water for long periods of time. The uni should be extracted as soon as possible following removal of the sea urchin from its holding tank.

Preparation

Once the uni is removed from the shell, any membrane should be removed and the uni scooped out with a spoon or knife.

Scissors can also be used, entering the mouth of the sea urchin and carefully cutting around the mouth before cleaning the inside with salt water. The spines can be trimmed so the sea urchin is able to sit nicely on the plate for presentation.

Uni can be rinsed in salty water. It is not necessary to submerge them in an alum solution which is often used in Australia to prepare uni for sale in trays. Any unused uni can be stored in salt water in the refrigerator for the next few days.

This article originally appeared in Hospitality’s February issue. Subscribe here. 

Image credit: Gunata Production