CHAPTER 2HANDLING OF FRESH (Wet)

AQUATIC PRODUCTS Doname A. Reyes

Instructor I

PHF 100

A. Spoilage of Fresh Aquatic Products

Fish and other aquatic products are among the world’s most perishable commodities. Spoilage in aquatic products begins soon after death. Following the death of fish, blood circulation stops resulting in a series of changes within the muscle. The spoilage of fresh fish is complicated process for which no single factor is responsible, but, rather, it is a combination of several interrelated processes.

- Bacterial and enzymatic spoilage are largely temperature dependent.

- The higher the temperature, the faster the rate of spoilage.

- Fatty fish spoil faster than lean fish- Small-size fish spoil faster than large fish of

the same species.- Cold-water fish spoil faster than warm-water

fish- Round fish spoil faster than flat fishes.

What makes the fish spoil?

• 1. Bacteria • Bacteria- microscopic one-celled organisms

which are found in the environment. The flesh of the fish is sterile (free from bacteria) when they are alive, but large numbers of bacteria are normally present in the surface slime, on the gills, and in the guts.

• Freshwater fishes bacteria: mesophilic-gram positive. – 3 layers of cell wall and purple in color – Example: Micrococcus, Bacillus, Cornyformes

• Marinewater fishes bacteria: Psychrotrophic gram-negative- 2 layers of cell wall and pink in color.- Example: Pseudomonas, alteromonas, acinetobacter, flavobacterium, cytophaga and vibrio

• Bacteria are normally not harmful to healthy living fish since the fish’s natural defense keeps them under control. But as soon as the fish dies, the bacteria and the enzymes they secrete begin to invade the flesh through the skin, through the lining of the body cavity or through any puncture in the body. Bacteria secretes enzymes, which break down complex substances in the flesh into simpler substances resulting to spoilage.

• Not all the bacteria present in the fish are responsible for the spoilage of fish.

• In chilled fish, the most active specific spoilage organisms (SSO) are gram-negative, psychrotrophic rods such as Alteromonas putrefaciens and certain Pseudomonas, Vibrio and Aeromonas.

• Shewanella putrefaciens - a typical SSO for the aerobic chill spoilage of many fish from temperate waters.

• Bacterial spoilage does not start until the passage of rigor mortis.

• RIGOR MORTIS – is the progressive stiffening of muscle shortly after death. Rigor usually starts from the tail towards the head until the whole body becomes hard and stiff (inflexible).

What makes the fish spoil?

• 2. ENZYMES • Enzymes are protein substances present in the

muscle and in the gut of fish that initiate or speed up chemical reactions.

• At the death of fish, the normal regulation system stops to function and the supply of oxygen and energy production ceases.

• The cells begin a new sequence of processes characterized by the breakdown of glycogen (this process known as Glycolysis) – the degradation of energy-rich compounds.

• After death, the enzymes naturally act on the food in the gut tissue.

• Autolysis – the self-breakdown or self-digestion that results the weakening, softening and discoloration of fish tissues.

What makes the fish spoil?

3. CHEMICAL SPOILAGE • Spoilage of fish due to chemical changes

mainly occurs during storage in ice or in frozen condition.

3. CHEMICAL SPOILAGE

• 3 factors in chemical changes or rancidity of lipids:

• 1. Lipid autolysis -enzymatic hydrolysis with fatty acids, and glycerol as main product.

• 2. Auto-oxidation – the reaction of unsaturated lipid with oxygen.

• Oxidative rancidity in fish can result to serious quality problems such as rancid flavors and odors as well as discoloration.

• 3. Denaturation of proteins during frozen storage resulting to tough, dry and fibrous texture.

B. HYGIENE AND SANITATION

• HYGIENE – means the science of good health and in everyday use, it signifies cleanliness and freedom from the risk of infectious diseases.

• Indicator of hygienic processes in foods:1. absence of any food poisoning hazard

2. attractive in appearance, odor and flavor 3. presentable in customer

1. CLEANLINESS

• Cleanliness is needed at every stage of fish handling and preparation.

• Clean- means the absence of visible dirt or unwanted matter.

• Cleaning- the removal of soil, food residues, dirt grease or other objectionable matter (FAO/WHO 1983)

• Cleaning alone, however, will not reduce the number of microbes; hence a further treatment called “sanitation” or “disinfectant” is required.

• SANITATION- is the process of reducing the number of living micro-organisms (but not the spores) in the plant to a level judged safe by public health authorities.

• DETERGENTS and DISINFECTANTS OR SANITIZERS are used in hygienic cleaning procedure.

• DETERGENTS – loosen and help remove dirt such as fish slime and blood.

• SANITIZERS- kill actively growing microbes.• Ideal detergents would be characterized by:

1. good wetting capacity • 2. ability to remove soil from surfaces• 3. power to emulsify (Soften)• 4. capacity to hold material in suspension• 5. good rinsing property• 6. non-corrosive

• 7. compatible with other materials • 8. quick and complete solubility• 9. dissolving action on foods solids• 10. germicidal action• 11. complete water softening power• 12. non-toxic• 13. economical to use

• Efficient sanitizers or disinfectants do not basically kill all micro-organisms present but reduce their numbers to a level at which they can reasonably presumed to present no danger to health.

• A good sanitizer or disinfectant must possess the following properties:

1. Effective germicide2. Easy to dissolve in water3. Low level of toxicity4. Stable in concentrated form

• 5. Does not significantly corrode metal or plastic

• 6. Effective at low concentrations unaffected by water conditions

• 7. Safe to health in both concentrated and diluted form

• 8. Deodorize• 9. compatible with cleaning compounds• 10. Low persistence

• Sanitation or disinfectant can be made by:1. Physical treatments- such as heat, UV irradiation, or by means of chemical compounds.

2. Chemical Disinfectants – commonly used in the food industry include chlorine and cholorine compounds, iodophores, quaternary ammonium compounds, ampholytic compounds, peracetic acid and hydrogen peroxide (FAO/WHO 1983)

C. WAYS IN PREPARING FISH • The methods of preparing “wet” whole or

round fish either for chilling, freezing or processing vary according to the specific requirements of the user.

• The following are the most common forms of preparing whole or round fish:

• 1. Drawn Fish (Gutted) – fish that has been eviscerated or the entrails removed.

• 2. Dressed fish – Fish with scales, viscera, fins, head and tail removed. It is ready to cook or prepared particularly to improve presentation.

3. Steaks – These pieces are cross-section slices of a large, dressed fish. A steak is usually 2-3 cm thick.

4. Fillets- The meaty sides of the fish removed from the backbone and ribs. Fillets are practically boneless.

• Different kinds of fillets:a. Block (Butterfly or double)- formed by both sides of the fish, still joined by the uncut flesh and skin of the belly.

b. Cross-cut fillets – from the flat fish taken from each side as a single piece.

c. Quarter-Cut fillets – flesh from each taken off in two pieces

d. Single fillet- just one side of the fish. * Single, cross-cut and quarter fillets can be

skinless.

• 5. Sticks and Portions – sticks and portions are small elongated chunks (rectangles) of uniform size and thickness cut from the meaty portion (fillet) of the fish.

D. Characteristics of Fresh and Spoiled Aquatic Products

• The freshness quality and the extent of spoilage products after harvesting and prior to consumption are generally evaluated by using the human senses (sight, smell and touch).

Characteristics of Fresh and Stale Fish

CHARACTERISTICS Fresh Fish Stale Fish1. Odor Fishy Foul or sour2. Gills Bright Red Light Pink3. Slime Clear and few

on the skinCloudy and plenty on the skin

4. Eyes Clear, Transparent, bright and protruding

Cloudy and shrunken

CHARACTERISTICS FRESH FISH STALE FISH 5. Flesh Firm and elastic;

fingermarks do not remain

Soft and finger marks remain

6. Skin & Colors

Shiny and bright Dull and Pale

7. Scales Slick tightly to the skin

Loose and easily removed

8. Vent Pinkish or reddish

Brownish

9. pH 6.0 to 7.0 Below 6.010. Water test Sink in basin of

fresh waterFloat in a basin of fresh water.

Handling of Fresh Aquatic Products

• 1. Fish - Fish must be sorted according to species and

size without delay and kept at low temperature. The fish must not be handled frequently. Low temperature, cleanliness, speed and care are the important factors in maintaining the quality of newly caught fish.

• 2. Crabs - Crabs must not be handled frequently after

harvest because they are very delicate. - Adequate water circulation or seawater

exchange is necessary. - For short-term storage, crabs can be kept in

clean moist bags or boxes but the humidity must be high.

- Exposure to high temperature will weaken the crabs. To prevent damage due to fighting during transport, the crabs must be packed closely in wet straw or shaving.

• 3. Shrimps - Shrimps harvested from the wild and ponds should

be cleaned thoroughly and protected from high temperatures. Chilling of shrimps with crushed ice must be done immediately.

- 4. Lobsters- If possible, lobsters must be landed alive. If

harvested alive, they should not be damaged or stressed. They should protected from direct sunlight and kept moist at all times.

- If dead, lobsters must be beheaded to prevent blackening, and the tails must be washed thoroughly in clean seawater and chilled using crushed ice.

• 5. Squids and Cuttlefish Squids and cuttlefish must be cleaned well

and stored at low temperatures. Chilling in crushed ice or ice slurry will maintain their freshness.

• 6. SeaweedsSeaweeds that are harvested fresh for local

consumption should be washed in clean seawater then packed properly in baskets with banana leaves as covering.

•END…•THANK YOU!!!