ΚΑΤΑΨΥΞΗ ΑΛΙΕΥΜΑΤΩΝ ΜΕΘΟΔΟΙ ΚΑΤΑΨΥΞΗΣ

ΚΑΤΑΨΥΞΗ = ΜΕΘΟΔΟΣ ΕΠΕΞΕΡΓΑΣΙΑΣ ΚΑΤΆ ΤΗΝ ΟΠΟΙΑ ΣΧΕΔΟΝ ΟΛΟ ΤΟ ΝΕΡΟ ΣΤΟ ΨΑΡΙ ΕΧΕΙ ΜΕΤΑΤΡΑΠΕΙ ΣΕ ΠΑΓΟ ΜΕ ΤΗΝ ΑΠΑΓΩΓΗ ΘΕΡΜΟΤΗΤΑΣ ΚΑΙ ΤΗΝ ΜΕΙΩΣΗ ΤΗΣ ΘΕΡΜΟΚΡΑΣΙΑΣ (Whittle and Howgate, 2002).

1. Air blast freezers ΚΑΤΑΨΥΚΤΗΣ ΜΕ ΡΕΥΜΑ ΨΥΧΡΟΥ ΑΕΡΑ (Batch air-blast) ΣΗΡΑΓΓΕΣ ΚΑΤΑΨΥΞΗΣ (Continuous air blast freezers) ΚΑΤΨΥΚΤΕΣ ΕΜΒΑΠΤΙΣΗΣ ΄Η ΚΑΤΑΙΩΝΙΣΜΟΥ ΣΕ ΨΥΚΤΙΚΟ ΥΓΡΟ Fluidized and semi-fluidized freezers

Batch air-blast

Continuous air blast freezers

2.ΠΛΑΚΟΕΙΔΕΙΣ ΚΑΤΑΨΥΚΤΕΣ(Plate or contact freezers)

3.Spray or Immersion freezers

Fluidized and semi-fluidized freezers

Product Initial Temperature (C) Operating temperature Freezing time Table 1.1.3.4-1 Freezing times for fish products. From Nicholson (1969). Product Freezing Method Product Initial Temperature (C) Operating temperature Freezing time Hour Min Whole cod, block 100mm thick Vertical plate 5 -40 3 20 Whole round fish , 125mm thick Air blast 5m/s -35 5 00 Whole herring, block 100mm thick Whole herring, 50mm thick on metal tray 4 m/s 1 40 Cod fillets, laminated block 57 mm thick in waxed carton Horizontal plate 6 1 20 Haddock fillets, 50mm thick on metal tray Air blast 4m/s 2 05 Whole lobster 500g 8 3 00 Liquid nitrogen spray -80 0 12 Scampi meats 18 mm thick Air blast 3m/s 0 26 Shrimp meats Liquid nitrogen 0 05

Bulk freezing in a batch air blast freezer room 1 Freezing method Freezing rate (mm/h) Bulk freezing in a batch air blast freezer room 1 Quick freezing in a tunnel air blast freezer 3 to 5 Plate freezing 12 to 25 Quick freezing in a continuous air blast freezer 15 to 30 Freezing in liquefied gases 30 to 100

Fish product Storage life, months -18°C -25°C -30°C Fatty fish 4 8 12 Storage life of frozen seafoods. From FAO (1977) Fish product Storage life, months -18°C -25°C -30°C Fatty fish 4 8 12 Lean fish 18 24 Flat fish 9 Lobster, crabs 6 15 Shrimp

Percentage of weight loss Weight loss from fish during freezing * Product Method of freezing Percentage of weight loss IQF** shrimp Air blast 2 to 2.5 IQF haddock 1.2 Carbon dioxide freezer 0.6 IQF products Liquid nitrogen freezer 0.3 to 0.8 Tray of fillets 1.0 Large fish or blocks 0.5 Blocks of fish Contact freezer (metal to fish contact) Cartons of Fish 0.5 within pack