Ice and cooling Icelandic International Development Agency (ICEIDA) Iceland United Nations University Fisheries Training Programme (UNU-FTP) Iceland National.

Presentation on theme: "Ice and cooling Icelandic International Development Agency (ICEIDA) Iceland United Nations University Fisheries Training Programme (UNU-FTP) Iceland National."— Presentation transcript:

Ice and cooling Icelandic International Development Agency (ICEIDA) Iceland United Nations University Fisheries Training Programme (UNU-FTP) Iceland National Aquatic Resources Research and Development Agency (NARA) Sri Lanka Department of Fisheries and Aquatic Resources (DFAR) Sri Lanka Quality and safety issues in fish handling ----- A course in quality and safety management in fishery harbours in Sri Lanka NARA, DFAR, ICEIDA and UNU-FTP

Content Properties of ice Thermal properties of fish Different types of ice Use of ice for cooling of fish for keeping fish cold

Learning objectives After this lecture the participants will know: correct use of ice how to estimate the amount if ice needed in various situations

Temperature Rate of activities (Enzymatic, Microbiological and Chemical reaction) Rate of Spoilage Shelf Life Purpose of cooling

Why use ice? Ice has a high cooling capacity and melts at a definite temperature (0°C) Ice is used to cool the fish to preserve it’s quality Ice keeps the fish moist and will wash surface bacteria, blood and slime from the fish as it melts Clean ice is harmless and relatively cheap Ice keeps fish cool during storage and transport

Availability of ice The availability of ice depends on: availability of clean water an ice plant at the harbour site The quantity of ice needed in a harbour depends on the quantity of fish passing through the harbour the number of one day vs. multi day boats the surrounding temperature and sea temperature the transport distance from harbour to the next link

Properties of ice and water Ice melts at 0°C 80 kcal are needed to melt 1 kg. of ice 1 kcal needs to be removed from 1 kg water to cool it by 1°C

Properties of ice, cont. 1 kg of ice can cool roughly 3 kg of water from 25°C to 0°C 1 kg ice + 3 kg 25°C water = 4 kg 0°C water + =

Thermal properties of fish Depend on fish composition mainly water and fat content LeanSemi fatFatty % fat< 1< 10< 20 Kcal/kg °C0,880,830,78 Kg fish cooled from 30->0°C by 1 kg ice 3,03,23,4

Thermal properties of fish, cont. In reality more ice is needed due mainly to heat loss to the surroundings during cooling surrounding air fish hold / box water that may be present etc..... More ice is also needed to keep the fish cool for any length of time

How does ice cool Ice cools by melting the ice takes up heat from the fish and melts The melted water (0°C) can further cool the fish when it flows over it

Cooling rate Cooling rate depends on Type of ice (flake, crushed block, slurry...) Adequate contact of ice with the fish Fish size (surface/volume) small fish cool faster than big fish Fish species fat and water content fish with thick skin cool slower than fish with thin skin

Types of ice and cooling media Flake ice Block ice and crushed block ice Ice slurry Liquid ice Chilled seawater Refrigerated seawater Dry or gel ice

Flake ice Larger heat-exchange surface : faster and more efficient Slightly sub cooled easy to store and handle Ready to use, less handling than block ice Flake ice

Block ice Produced in large chunks Big ice chunks melt slower than small (surface/volume) Can be transported before crushing Particle size depends on crushing machine

Ice slurry Flake or block ice crushed to small ice particles and mixed with seawater or water Good for cooling Not as good for keeping cool unless drained Stagnant blood water salt uptake

Liquid ice Very small ice particles form in salt water / seawater Very good cooling properties Not as good for keeping cool unless drained stagnant blood water salt uptake

Chilled Sea Water (CSW) Seawater and ice mixed in a container or hold agitated by blowing air up through the mixture Good for quick cooling Salt uptake can be a problem if fish is in CSW for a long time

Refrigerated Sea Water (RSW) Seawater cooled by mechanical means seawater is circulated from fish container/hold, through a refrigirating unit and back to the container/hold Good for quick cooling Salt uptake can be a problem if fish is in RSW for a long time

Properties of different types Ice liquid mixtures +RSW completely surround the fish have good heat transfer properties cool fast In case of seawater salt uptake can be a problem if fish is kept long in the mixture

Properties of different types, cont. Ice particles (flake ice and crushed block ice) cool slower (do not completely surround fish) have lower heat transfer no problem with long time storage (no salt uptake) cleans the fish as it melts

Bulk density of various types of ice Flake ice4-500 kg/m 3 Tube ice5-600 kg/m 3 Block ice 6-700 kg/m 3 Ice920 kg/ m 3 Ice slurry/liquid ice850-900 kg/m 3

Time of cooling Depends on: type of fish (thermal properties) initial temperature of fish type of ice shape of fish (thickness) size of fish method of iceing

Cooling rates in the center of cod - comparison of flake ice and liquid ice Temp. (°C) Time (hours) Liquid ice Flake ice

Amount of ice needed The amount of ice needed depends on: temperature of fish surrounding temperature and conditions is the fish kept in isolated boxes is the fish hold isolated etc... the length of time the fish is to be kept on ice storage on board transport Transport with ice and coolingTransport with ice

Amount of ice – cooling fish 100 kg of fatty fish at 25°C needs to be cooled to 0°C with ice - 1 kg of ice can take up 80 kcal og heat when melting - to cool 1 kg of fatty fish by 1°C 0,78kcal have to be removed How much heat to remove? 100kg * 25 °C * 0,78 kcal/kg °C = 2610 kcal How much ice will that melt? 2610 kcal / 80 [kcal/kg ice] = 32.6 kg of ice OR ABOUT 1 KG ICE pr. 3 KG FISH

Amount of ice – keeping cool Very difficult to estimate Depends on the conditions duration weather degree of insulation where in hold/vehicle the fish is kept Experiments have been made...

Results of ice meltage tests Results of ice meltage tests under field conditions. (·) plastic box in the shade, (x) plastic box in the sun. Plastic boxes, 40 kg capacity, red colour, unstacked, flake ice, external average temperature (dry bulb) 28°C. (Data obtained during the FAO/DANIDA National Workshop on Fish Technology and Quality Control, Bissau, Guinea-Bissau, March 1986) importance of insulation Quality and quality changes in fresh fish FAO FISHERIES TECHNICAL PAPER – 348 H. H. Huss

Results of ice meltage tests Results of ice meltage tests under field conditions. ( · ) standard plastic box (not insulated) 40 kg total capacity, (x) insulated plastic fish container (Metabox 70, DK). Both kept in the shade, un- stacked, flake ice, average external temperature (Te) 28°C. (Data obtained during the FAO/DANIDA National Workshop on Fish Technology and Quality Control, Bissau, Guinea-Bissau, March 1986) importance of insulation Quality and quality changes in fresh fish FAO FISHERIES TECHNICAL PAPER – 348 H. H. Huss

Results of ice meltage tests Results of ice meltage tests during storage in a stack of plastic boxes. Plastic boxes 35 kg in a chill storage room at 5°C, flake ice (from Boeri et al. (1985) importance of placement By insulating around the storage area (transport truck, ship hold...) differance in ice melting rates can be reduced Quality and quality changes in fresh fish FAO FISHERIES TECHNICAL PAPER – 348 H. H. Huss

Amount of ice - example 200 kg of tuna needs to be cooled from 28°C to 0°C and transported for 4 hours at surrounding temperature 28°C The tuna is packed in polystyrene boxes (70X50X50cm). If the tuna is transported in an uninsulated truck 22 kg of ice is needed during transportation Approx. 65 kg of ice is needed to cool the tuna If the tuna is transported in an insulated, refrigerated truck at 3°C 2 kg of ice is needed during transportation

Methods of icing raw material There are two main methods of icing raw material: Direct Contact Icing (DCI): suitable for icing of fish and shrimp. Non-Contact Icing (NCI): suitable for icing of squid, cuttlefish and octopus. (Bao, Quang, Vn-pr., 2003)

Non-Contact Icing Method (NCI) Raw material is individually packed in polyethylene bag. Raw material is packed in layer with plastic sheet and ice. (Bao, Quang, Vn-pr., 2003)

Handling ice Ice used for cooling fish needs to be handled with the same care as the fish itself contaminated ice means contaminated fish Ice should be kept in insulated boxes/places will minimize melting prior to use

Quality and safety of ice Depends on: quality of water conditions in production (hygiene etc..) storage of ice handling of ice The ice is part of the processing/product

References Shawyer, M.; Medina Pizzali, A.F. The use of ice on small fishing vessels. FAO Fisheries Technical Paper. No. 436. Rome, FAO. 2003. Graham, J.; Johnston, W.A.; Nicholson, F.J. Ice in Fisheries FAO Fisheries Technical Paper. No. 331. Rome, FAO. 1992. Training material from UNU-FTP/Icelandic Fisheries Laboratories

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