AIST Stories No2

24From AIST to the Innovative Worldcooled, freshness can be retained. Furthermore, fine ice particles do not disfigure the fish. Hokkaido-based machinery manufacturer Nikko wanted to manufacture a low-cost, higher-performance sherbet-like ice-making machine; hence, they commenced development efforts. Nikko approached AIST for technical advice; in 2010, joint development of an ice-making machine commenced.Cumulative fundamental research into how to make iceTakaaki Inada was charged with developing the ice-making machine. Originally, he was a researcher conducting research and development related to sherbet-like ice for air-conditioning. “In ice thermal storage systems*2 used in air-conditioning units, supercooled water is increasingly being used to make sherbet-like ice. This is because this method is superior to others in terms of energy efficiency. However, here we are talking about installing such a system in a fishing boat so we need to consider making it as compact as possible. I thought that a scraping system would be best suited to making a large quantity of sherbet ice as quickly as possible on a fishing boat.”Developing the equipment was a process of trial and error. Ice cooled to around –15°C would adhere strongly to the cooled solid surfaces. Scraping ice from there sometimes broke the scraper blades. So, an observation apparatus resembling an ice-making machine was built, and the appearance of ice under various conditions inside the ice-making machine was researched. Through these tests, it was determined that the appearance of ice being scraped is classified into two types depending on the salt concentration. By making two types of ice, the salt concentration of the seawater could be adjusted. When the salt concentration was low, the ice crystals were crushed to make ice; when the salt concentration was high, ice was generated via peeling the ice off from the solid surfaces of the inner walls of the cooled ice-making machine. Through Sherbet-like brackish ice for preserving freshness of seafoodFreshness is vital! AIST technology delivers delicious fish to the tableApplications expected in the medical and food fieldsThermal and Fluid System Group, Energy Technology Research InstituteDevelopment of an ice-making machine for fresher, more delicious fishAn important part of Japanese cuisine is the savoring of raw seafood. The Japanese are very particular about the freshness of seafood; already the control of freshness from the fishing ground to the table is of a high level. However, those in the fisheries industry sought an even more advanced freshness retention technology. Furthermore, there was a desire to deliver to tables throughout the nation fresh, delicious seafood that could be enjoyed by all.The freshness of fish is greatly influenced by the ability to swiftly disable the fish when it is landed, a process known as “ikejime”*1, before it can flop around; also important is the extent to which temperature can be controlled appropriately. However, it is not easy to execute the ikejime process for a large quantity of fish onboard. In place of this process, a method that employs sherbet-like brackish water ice comprised of fine ice particles has come to be employed. Preserving fish with sherbet-like ice means they end up dying without flopping around: because they are rapidly Manufacturing technology for sherbet-like brackish ice that can retain the freshness of seafood for longer and keep it in better condition. By using this technology, not only can fresh, delicious seafood be delivered to the table, but one can also anticipate that local fisheries and industries could be revitalized through branding of their seafood. Furthermore, the technology could potentially be applied to and contribute to the food (frozen food etc.) and medical (low-temperature surgery etc.) fields. AISTsupporting livelihoods! Our life and society will change in this way!