Slurry Ice

Slurry ice consists of tiny ice particles suspended in water, creating a slush-like consistency that allows it to adhere completely and seamlessly to the surface of the fish or other items being cooled. Because no air gaps remain, it cools rapidly—several times faster than standard ice water and dozens of times faster than cube ice—instantly halting microbial growth and autolysis.

Furthermore, slurry ice made from saltwater maintains an optimal temperature range of approximately 0°C to -2°C. While this is below the freezing point of fresh water (0°C), it remains above the temperature at which fish cells freeze and rupture; this allows the product to be kept at the “ice-temperature zone” (Hyoon®)—the temperature just above freezing where freshness is best preserved—without actually freezing the fish.

MECHANISM

Mechanism

Countless ultra-fine, spherical ice particles—ranging from a few millimeters to tens of micrometers in diameter—float within the water (or saltwater). Thanks to its fluidity, the mixture penetrates the fish’s contours, including the gills and mouth, ensuring 100% surface contact without gaps. This facilitates instant heat transfer from the fish to the ice.

FRESHNESS

Freshness Retention

Freshness is assessed by the appearance of the silvery belly, yellow mouth, and back color. The image below demonstrates that slurry ice is superior to crushed ice in preserving freshness.

Freshness can also be gauged by the state of rigor mortis.

  

COMPARISION

Comparison of Cooling Effects

The figure below illustrates cooling rates. Crushed ice has a slower cooling rate than slurry ice and fails to maintain sub-zero temperatures. This slow cooling allows fish to thrash about, causing blood to circulate through the body and lactic acid to build up—factors that accelerate the loss of freshness. The rapid cooling provided by slurry ice simultaneously achieves two essentials for preserving seafood freshness: preventing fish from thrashing and maintaining low temperatures below 0°C.

REPRODUCIBILITY

Slurry Ice Maker

Nikko’s “Kaihyo” slurry ice maker is designed specifically for fishing vessels. Its smallest model measures just 1,350 mm (L) x 1,070 mm (W) x 1,350 mm (H), making it compact enough to be installed on fishing vessels of 19 tons or less.

Its greatest advantage is the ability to produce slurry ice directly from seawater. Onboard ice production allows the quantity of ice to be adjusted according to the catch volume. This reduces the time and labor required to load ice and cuts fuel costs by eliminating the need to carry excess ice weight.