Slurry-Ice: An opportunity in quality improvement

An increasing demand for a better quality of fish produced at sea generates new handling techniques. Rapid cooling is essential for the product to reach optimum quality, and the industry is looking for better methods to utilize ice, either as a premium cool­ing material or as a booster coolant in parallel with RSW.

The beauty of using ice is its ability to store large amounts of energy; it can store up to 80 times more energy than can cold water. This is well known to anyone who uses ice. There are, however, different options on which type of ice is most suitable and indeed the purpose to which the ice will be put often determines the type of ice that is selected for use. Tradition was also of importance in choosing the type of ice that is going to be used.

While all the various types of ice are simi­lar in terms of the amount of stored energy, the differences occur in the various ice-types surface characteristics, and in its storage and handling requirements.

Handling ice can in many cases be very difficult, as humidity, temperature and condensation often influence the quality of the ice. In most cases the key is in the storage and distribution by shoveling, blowing or conveyor, of the ice from its storage point to designated areas or cargo holds. Ice-Tech Systems from Norway have developed a "new" method of handling ice on board a fishing vessel, namely "Slurry-ice". The method of making slurry-ice is in itself quite ingenious since the process also gives the benefit of producing salt free ice direct from sea water

As slurry-ice is generated from seawater, it is also pumpable and can be distrib­uted through pipes down to a diameter of 32 mm. This makes it ideal for use in boosting the capacity of an existing RSW plant as slurry-ice can be injected directly into existing pipes to boost the capacity rather than extending the pipe sizes when increasing the chilling capacity. Slurry-ice is also used onboard seiners to boost the chilling curve when fishing for the con­sumer market, the use of slurry-ice ena­bles the chilling of 100 tons of catch in less than one hour.

By hooking up the slurry-ice generator to the RSW tanks, and producing slurry that can float on top of the tanks, the generated heat is removed very rapidly from the catch.

Ice-Tech is also carrying out tests on the use of slurry-ice on summer capelin and blue whiting. These species are sus­ceptible to sail absorption, and the present techniques to reduce these prob­lems includes the use of fresh water in the RSW, or mix saltwater with ice, or sim­ply using ice-bits stored in seawater and gradually mixed with the catch as it is pumped on board in order to keep the catch as "dry" as possible.

Onboard freezer and factory trawlers, slurry-ice is used with great success, it is used to chill receiver bins and bleeder tanks and is said to boost the ca­pacity of the factory. Another benefit is that the processing time in the factory can be extended when using slurry-ice.

The ice is generated at a constant base as incoming sea water is pre-chilled and converted into the slurry of about 10 % ice fractions. The slurry is pumped to the bleeder tanks or receiver bins and accu­mulates energy between the hauls and in the process time.

Exercise 2. Answer the following questions:

1. What generates new handling tech­niques?

2. What are the advantages of using ice?

3. What types of ice are used in industry?

4. Where do the differences occur?

5. Why can handling ice be very difficult in many cases?

6. What new method has been developed?

7. What are the characteristics of slurry-ice?

8. Where can it be used?

9. What species is Ice-Tech also carrying out tests on?

10. What are the benefits of using slurry-ice in the factory?

Exercise 3. Speak about the advantages of using ice for fish preservation.

Exercise 4. Translate from Russian into English:

^{a) Технологический процесс переработки рыбы и морепродуктов предусматривает обязательное их охлаждение или заморозку на стадии транспортировки и хранения. Продукты должны иметь правильную внешнюю форму и не терять в качестве. Для замораживания рыбопродуктов на рыбодобывающих и рыбоперерабатывающих предприятиях широко используются плиточные скороморозильные аппараты. В их состав входят блоки из горизонтальных плит, гидравлическая станция, холодильная установка и щит управления.}

^{b) Процесс замораживания осуществляется следующим образом: блок-формы, изготовленные из нержавеющей стали или пищевого алюминия, с рыбой и морепродуктами помещают между плитами аппарата. Плиты сжимаются, создавая определенное усилие прессования продукта и хороший тепловой контакт. Внутри плит кипит при низком давлении холодильный агент, отбирая тепло от замораживаемой рыбы. Непосредственный контакт продуктов с охлаждающими плитами интенсифицирует их охлаждение и замораживание. Процесс замораживания длится 1,5–2 часа.}

^{c) Растущая конкуренция между предприятиями рыбной промышленности подталкивает на использование новых технологий для производства и хранения продуктов питания, которые связаны с использованием чешуйчатого льда. Чешуйчатый лед обладает высокой охлаждающей и абсорбционной способностью и применяется в рыбном хозяйстве для охлаждения и хранения свежей рыбы без потери качества. Применение чешуйчатого льда увеличивает срок хранения свежей рыбы с 1 до 10 дней. Для охлаждения 1 т свежей рыбы с температуры 26 °С до 0 °С потребуется около 250 кг чешуйчатого льда.}

^{d) Чешуйчатый лед – сухой и переохлажденный, чем обусловлена его абсорбционная способность. Производимый лед – рассыпчатый, не слипается в блоки, что позволяет, при необходимости, его транспортировать пневматическим методом и хранить в низкотемпературных камерах. Лед вырабатывается без острых углов и кромок, благодаря чему он не портит внешний вид продуктов и упаковки.}