CHAPTER 3 Chilling.pptx
- 1. CHAPTER 3 Chilling 1. Fundamentals of Chilling 2. Methods of Chilling 3. Methods of Storing Iced Fish 4. Types of Containers 5. Types of Insulation 6. Chilling on Board 7. Quality Changes of Fish During Chilling 8. Handling Chilled Fish
- 2. • Fish is highly perishable- proper handling must start from the moment it is harvested until it reaches the consumer’s table. • Lowering the temperature (chilling, refrigeration and freezing)is the key factor in maintaining the quality of fresh fish • Chilling is the most common practice in keeping the freshness of fish.
- 3. Methods of Preserving/Processing Fish Temperature Control Use of Packaging technologies Other Processing Methods Use of Additives Removal of Moisture
- 4. Chilling -means the reduction of temperature to some point below (-1.1 to -2.2⁰C) or above (0⁰C) the freezing point of the fish muscle. Chilling does not stop spoilage but slow it down considerably.
- 5. Methods of chilling 1. Wet Ice (Icing) 2. Chilled Seawater Ice 3. Other Methods
- 6. • WET ICE (ICING) - Icing is by far the most common and useful way of chilling the fish catch. • Cooling is effected by the direct contact between the melted ice and the fish. • When ice is place in close contact with the fish, heat is transferred from the warm fish to the ice resulting to the melting of ice; in turn the fish is cooled down by the melted ice. Methods of Chilling
- 7. WET ICING (ICING) • Direct contact between melted ice and fish • ICE- an ideal cooling media; with very large cooling capacity • -harmless, comparatively cheap, can quickly cool • -occurs I different forms: crushed, tube, flaked, blocks
- 8. Factors to be considered when icing 1. Sufficient ice must be used to maintain fish temperature at 0 ⁰C. • For longer trips more ice than fish is needed , more than the usual 1: 1 ice ; fish ratio, 2. The arrangement of ice and fish must be in such a way that accumulated water, blood and slime can be drained easily. 3. Ice and fish should be placed alternately to avoid localized heating. Fish must be sufficiently surround with ice on the sides, top and bottom
- 9. 4. When packing mixed fish, big fish must be placed at the bottom and small fish on top. • Fish with delicate skin should be packed on top of fish with scales. 5. Gutted fish must be filled up with ice in the belly cavity • must be arranged with belly down in a slanting position inside the container.
- 10. - This is also termed as “slush ice ”which is a mixture of seawater and crushed ice used for chilling of fish catch. - The amount of ice depends on the initial temperature of the water and the fish, size of the container and the quality of its insulation, and the length of the trip. The advantages of CSW over icing are: 1. CSW chills fish much faster than wet ice. 2. Fish is CSW do not suffer from physical damage due to crushing or pressure from other fish. 3. Fish in CSW are washed in the slurry. 4. CSW chilled fish do not necessarily keep longer than wet iced fish. 2. Chilled Seawater Icing
- 11. – a mixture of seawater and crushed ice Advantages: *CSW chills fish much faster than wet ice *Fish do not suffer from physical damage due to crushing of pressure from the other fish Disadvantages: * Do not necessarily keep longer than wet ice 2. Chilled Seawater Icing
- 12. A. Refrigerated Air: commonly done in big commercial boats. chilled air is circulated by a finned evaporator and fan B. Gel Ice Mat Freezing water-based gel Suitable for air transport No water leakage during thawing Other methods:
- 13. 3. Dry ice o Dry ice is sold carbon dioxide. Cooling is effected by the evaporation of the dry ice. o Due to its very low temperature (78.9C), dry iced should not be used in direct contact with fish to avoid cold bums. o This method of chilling is preferred for air shipment of fish as this does not cause leakage. o However, the use of dry ice is subject to restrictions because it expands from a solid form into a gas and may be expel oxygen, posing a hazard to the safety of airplanes.
- 14. Types of Ice: Block Ice Crushed Ice Flake Ice Tube Ice Rarely used directly for cooling Irregular size, sharp edges, can physically damage fish commonly produced from FW as thin flakes, formed instantly on cold metallic surfaces Lasts longer, melts more evenly, useful for transporting fish in uninsulated containers
- 16. Methods of storing iced fish: SHELFING BOXINNG BULKING
- 17. BULKING • Fish are layered to achieve intimate contact Advantages Disadvantages Economize space; utilized in the hold of fishing boats When a very large volume of fish needs to be stored
- 18. • Fish is stored in a single layers, gut cavity down on a bed of ice; a little ice is spread on top (to ensure bleeding through the cut surface; retard spoilage) • applicable to large which are • fish can be separated into different catches Shelving
- 19. Boxing • The preferred method of storing iced in fish • Fish and ice are layered in specially made boxes Advantages Disadvantages Easy segregation of first caught, small from large, etc. Minimum handling and with good boxing practice, fish will not damaged physically Space occupied in storage is greater than that for bulking
- 21. Types of Containers: • insulating properties • proper shape and dimension for the fishery product concerned • easily to handle, fill and empty • easy to clean and stack securely one on top to another • constucted from non poisonous materials • adequated provision for drainage of melt-
- 22. Types of containers: 1. Plastic Boxes 2. Galvanized Iron Sheets Tubs 3. Wooden Boxes 4. Coconut, Bamboo, or Rattan Baskets
- 23. • *High density polythylen (HDPE) and polypropylene are widely use in the manufacture of modern day containers. • Polyethylene: • Polyethylene(PE) is made by subjecting gaseous ethylene monomer to heat and pressure in the presence of a metalic catalyst. • PE is classified into low density (0.910 to 0.925 g/cm medium density (0.926 to 0.940 g/cm and high density TYPES OF Plastic Boxes
- 24. • *high density polyethylene is divided into type III (density0.941 to 0.959 g/cm, and type IV which has a density of 0.960 g/cm and above
- 25. Polypropylene (PP) - Is a homo-polymer of propylene. It has low density (around 0.902 g/cm and superior processability. It is one of the lightest plastics, has a good resistant to grease and most chemicals, provides a good barrier to water vapor and can withstand high temperatures due to its high softening point. Polypropylene is more rigid, stronger and lighter than polyethylene Polystyrene (Styrophore)
- 27. Tubs made from GI sheets (Baiiera) are conical in shape and so far the most commonly used container by fishers in the Philippines. These tubs are not provided with drains; they easily corrode they have poor insulating property and are quite difficult to handle due to their fill capacity, around 40-50 kg. Baheras are becoming less popular locally and are slowly being replaced by polystyrene boxes. Wooden Boxes: Wooden boxes can withstand rough handling and have relatively good insulating property However, they are not easy to clean, and are slightly difficult to handle because of their weight They become a hazard to handlers ( splinters can cause injury) when they are not properly maintained Galvanized Iron (GI Sheet Tubs (Baftera)
- 28. Pointers in Handling Chilled Fish The choice of insulating material will depend on its thermal conductivity or resistance and permeability to water vapor (waterproof), density and compressive strength.
- 29. • The following must be taken into consideration when handling chilled fish: 1. Temperature 2. Time 3. Contamination 4. Damage