Some people say that “Sea urchin in a wooden box (called ‘hako-uni’ or ‘ori-uni’ or ‘boxed sea urchin’) has a bitter medicine taste”. When a sea urchin loses its freshness, its starts to disintegrate so an additive called alum is used to maintain its shape. If you’ve ever tried a sea urchin that tasted bitter*, this may be the reason.
Sea urchin soaked in brine without using alum (called ‘ensui-uni’ or ‘saltwater sea urchin’) is also commonly found. There is also a new technology that doesn’t use alum. In this method nitrogen water (water from which oxygen has been removed and then nitrogen dissolved) is used when sealing. The effect of replacing oxygen with nitrogen is inhibited oxidation, maintaining freshness of the sea urchin.
*An “off flavor” that takes away from the primary good tastes.
We hope this information will be helpful.
Revision date: April 18, 2017