Ice slurry is preserving product freshness around the world

Deepchill, the trademarked name for a product developed by the Canadian company Sunwell Technologies, is a cooling and preservation medium comprised of millions of ice micro-crystals suspended in a liquid solution to form an ice slurry. The micro-crystals surround the entire surface area of the product being cooled, giving it the ability to chill at least three times faster, and store a few degrees colder for a longer period than conventional ice. The slurry also suspends and protects the product from bruising, bacterial growth and tissue degradation.

Over the last 30 years the company’s slurry production systems have been successfully installed onboard various types of fishing vessels around the world. The installations reveal that the slurry maintains the freshness of the fish throughout the cold chain, ensures top quality product and higher yields, which translates into higher profits.

Deepchill slurry ice is used for chilling pelagic fish in the fish hold

Hoki fillets retain their freshness for up to 18 hours

To achieve the fastest cooling in the fish receiving pond or the chilling tank, the ice concentration in the slurry is often set around 20%. Systems serving this purpose can be found, for example, onboard freezer trawlers of Sealord, New Zealand installed in the mid 1990s. The vessels catch hoki, a species that quickly deteriorates at higher temperatures. As with any filleting vessel, fish move through the factory at a relatively constant rate, yet they are dumped into the receiving ponds every two to three hours. This results in the product remaining in the ponds for several hours. Without cooling, the temperature increases and quality drops dramatically.

A Deepchill system with 16 mt daily ice capacity and 4.5 cubic metre storage capacity was designed and integrated into the vessels’ factory decks. The slurry with 25% ice concentration is delivered into four fish receiving ponds shortly before and during catch arrival. Hoki arriving at 12 - 15°C is quickly cooled to 0°C. Because of the excellent preservation effect of the slurry, the vessels are able to process product up to 18 hours old from the receiving ponds into "A-Grade" skin-off fillet, and the yield rate from the filleting machines also increases due to the firmer product being put through them. Another benefit is that the texture and colour of the fillets is much more consistent and closely resembles that of freshly caught product. During some stages of the hoki season the fish is only caught during the day, so the ability to catch larger bags at the end of the day and process the fish throughout the night without loss of quality has also proven invaluable. The installations paid for themselves in the first six months of operation.


Different ice fractions for specific needs

For fishing vessels delivering fresh fish in bins or boxes, low ice concentration slurry ice systems are not an ideal option. When icing the fish bins or boxes, the thinner slurry could easily run off through the drain holes, while a significant part of the system’s refrigeration capacity is consumed to produce the large volumes of cooling water, rather than ice crystals. To address the problem, Sunwell developed a system capable of producing ice slurries in varying ice consistencies for use in fish receiving ponds and fish storage bins. Since 2001, this type of the system has been adopted onboard many fishing vessels, including Pesca Chile S.A.’s fishing fleet.

Onboard Pesca Chile’s wetfish trawlers and longliners, the temperature of fish when it arrives in the receiving ponds can be as high as 15 °C. A slurry with a lower ice fraction of 15 to 20% is pumped and sprayed into the receiving ponds to immediately reduce the temperature of the large quantities of fish. The fish is kept there until it can be sorted by size and boxed. A thicker slurry with an ice fraction of 40 to 50% is pumped directly into the boxes leaving the fish firmly packed and cradled in ice crystals. The boxes are kept in a fish hold for the duration of the fishing trip. Mr. Paulino Martino, Head of the Technical Department, says: “We are pleased with the benefits of the slurry ice and the way the quality of our product has improved by using it”


Adjustable salt concentration

One of the Sunwell’s recent developments is the introduction of the world's first onboard low salinity system for Hokubu Makiami Gyogyo Inc. of Japan in 2006. The equipment was installed aboard its 300GT purse seiner "Hokusho Maru" which fishes tuna or skipjack from April to October, and mackerel and sardine from November to February. The system has 20 mt daily ice capacity and includes a compact, patented separator/dispenser tank which separates saltwater from the slurry. The ability to adjust the ice concentration by up to 60%, and the salt content in the range of 2 to 3%, ensures maximum preservation without damage to or excessive salt uptake by the fish. According to the company’s division manager, Mr. Sakurai, “the fish caught can be quickly chilled onboard preserving the the product’s freshness more effectively than crushed ice. In addition, it does not hurt the surface of the fish – and it saves labour”

Continuous innovation is the key to Sunwell’s success in the industry. Two of its latest installations onboard the paired trawlers “Heykur” and “Falkur” delivered to Faroe Seafood in early 2008 include a computer-based automatic monitoring and diagnostic package. A sophisticated touch panel allows operators to monitor and record the operating parameters, while office personnel can track the system’s operations online, and even change the system settings.

For more information, contact:

Dr. Ming-Jian Wang
Technical Sales Manager
Sunwell Technologies Inc.
180 Caster Avenue
Woodbridge, Ontario
Canada L4L 5Y7
Tel: +1 905 8560400
Fax: +1 905 8561935