Ikura is salmon roe. It particularly refers to the eggs harvested from salmon just before spawning and that have been removed from the membrane. Another name for ikura (salmon roe) is barako. Usually they are not cooked or processed, but eaten after pickling in brine or soya sauce.
The term ikura is derived from the Russian word 'ikra' which means roe or small round things. In Russian, caviar and cod roe are also called 'ikra' however in Japan ikura refers only to salmon roe. Salmon eggs are called 'red ikra' in Russian. On the other hand, 'black ikra' refers to caviar.
The Russian way of eating salmon roe entered Japan in the Taisho period when the Karafuto Prefecture (now Sakhalin) Fisheries Experimental Station test produced a salt cured product based on the manufacturing method from Russia. Now salmon roe is usually eaten with a little sweet soya sauce and is often used in dishes such as salmon roe on rice (ikura-don) or in sushi.
In Japan the most common roe is salmon roe however in Russia they use the roe of pink salmon (karafuto-masu), and products made with pink salmon in Japan are distinguished by names such as 'masu-ko' or 'masu-ikura.'
For the different names used for roe from other varieties of fish please refer to the item 'sujiko' (roe).
Sujiko roe is roe that is left in the sack whereas cod roe has been removed from the sack. Therefore, to process sujiko into ikura (salmon roe) it is necessary to rub it over a fine net like a racket. The membrane of the immature eggs is still soft and not suitable for this processing method, which is more suited to mature eggs. However, the eggs of fish that have already returned to rivers and started to swim upriver are virtually about to be let go and are very hard and not suitable for eating.
Salmon head south from the northern pacific around Kamchatka when it is time to spawn. In Hokkaido the ban on salmon fishing is lifted between the end of August and the beginning of September. Fishing begins in earnest in the pacific side of northern Japan and also in Niigata in November.
At the beginning of the open fishing season, the eggs are immature and small with weak membranes. Eggs harvested at this time are not only difficult to process but even to freeze. This is because the membranes are weak and fall apart when frozen. Roe harvested at this time is mainly sold as sujiko.
There is a little variation in the maturing period between the spawning regions, however on average in around October the eggs are mature and suitable for processing into ikura (salmon roe). By November the eggs are even more mature. The eggs are bigger and the membrane a little harder. If they mature further, the egg membrane will become too hard and remain in the mouth when eaten.
As the membrane of the salmon roe is difficult to digest, it is a protein likely to become an allergen.
In Hokkaido, families enjoy the taste of Fall by making ikura (salmon roe) from the sujiko, and they do this by putting the sujiko in hot water and carefully removing the membranes to make the 'barako' or loosened roe. Putting the roe in hot water makes the color turn white however the color returns after further processing.
During manufacture, the roe must not come into contact with fresh water. The egg membrane will harden in fresh water so sea water or water even saltier than sea water is used.
Consumption outside Japan
There are not many regions in the world other than Japan that consume salmon roe as it contains a lot of cholesterol. Even in Russia, which is the origin of the method of manufacture of salmon roe in Japan, people do not eat it as often as in Japan. Most salmon roe harvested in these regions is processed for export to Japan. Even the Inuit, who are said not to waste any resources, do not have the custom of eating salmon roe and discard the roe together with the innards as soon as they have caught the fish. In the United States and Canada salmon roe is not eaten but is canned in sugar and sold as fish bait.
In recent years Japanese food has experienced a boom in the United States and salmon roe has come to be well-known as a sushi topping. It is not common however packets of well preserved salmon roe can occasionally be found as delicacies at supermarkets.
Artificial salmon roe
These days, as the yield of natural salmon roe is insufficient, an alternative artificial salmon roe made from salad oil and seaweed extract available.
The look, texture and taste are virtually indistinguishable from the real salmon roe however the real salmon roe turns white when put in hot water due to changes in the protein. It is also used as a diet food as it is low calorie.
However, one of the ingredients, carrageenan, has been identified as having an adverse affect on the immune system.