Fish Products: Safety, Processing, and Storage
Sanitary and Toxicological Aspects of Fish
Toxicity and Intoxication
Freshly caught fish muscle is sterile. The presence of pathogenic germs is related to their presence in water or sediments. Contaminants include pathogenic bacteria like Vibrio parahaemolyticus and Clostridium botulinum.
Viral Infections
The presence of viruses is considered a potential risk, and they have been shown to survive for long periods in refrigerated and frozen mollusks.
Parasitic Diseases
Some parasites affecting fish can cause diseases in humans after eating raw or undercooked fish. The most frequent affliction is anisakiasis.
Toxicological Aspects
Fish can be contaminated by:
- Ciguatera poisoning
- Histamine poisoning
- Tetrodotoxin poisoning
Heavy Metals: Heavy metals can be found in the aquatic environment or seaside, as simple ions in solution or associated with organic particles. This leads to bioaccumulation along the food chain. Excessive ingestion of lead and mercury can damage the central and peripheral nervous systems. Cadmium causes emphysema, anemia, and cancer.
Other Products:
- Pesticides (organochlorine products)
- Lipid oxidation products: The high degree of unsaturation of fish lipids makes it very susceptible to autoxidation reactions after reacting with atmospheric oxygen in the presence of free radical initiators.
Fish Products
Dried Fish
Drying leads to lipid oxidation, partial protein denaturation, muscle shrinkage, the Maillard reaction, and vitamin destruction. After reconstitution, it is not possible to recover the initial characteristics.
Salted Fish
Examples include herring, cod, sardines, anchovies, tuna, and salmon. After salting, the fish undergoes a maturation process due to tissue and digestive enzymes, and bacterial fermentative action. This leads to the release of free fatty acids and an increased content of free amino acids, non-protein nitrogen, and amino acids.
Smoked Fish
Smoking is mainly done for organoleptic reasons, causing a set of modifications due to temperature. The most significant changes are water loss and protein tissue distortion.
Pickled Fish
The action of salt is joined by the acidification of the medium through the addition of diluted vinegar or acetic acid.
Preserved Fish
These undergo a soft sterilization process, are packed in airtight containers, and may be in their own juice or oil.
Fish Hydrolysates
These are produced by enzymatic proteolysis of fish tissues. They are normally presented in dried form, containing soluble protein peptides and amino acids, and possess interesting emulsifying and gelling properties.
Fermented Products
These can be divided into:
- Fish-paste sauces
- Salted fish
- Whole fermented fish
- Fish silage
Surimi-Based Products
Surimi is an excellent raw material for the elaboration of products that imitate others. From a nutritional point of view, these are high-quality products. Soluble proteins are eliminated with successive washes. The carbohydrate content is due to the addition of sugars, and the fat content is much lower than that of the original fish.
Alteration, Preservation, and Storage
Alteration
Alteration is characterized by changes in appearance, abnormal odors, and tastes. Some factors influencing the oxidation rate are:
- Percentage of total polyunsaturated fatty acids
- Presence of oxygen
- Storage temperature
- Exposure to light
The speed of alteration depends on:
- Species, size, and lipid richness
- The fish’s condition at the time of catch
- The size and nature of bacterial contamination
- Conservation temperature
Preservation and Storage
Refrigeration
Refrigerated fish preserves most of its nutritional value and organoleptic characteristics. It consists of placing crushed ice on the fish to maintain a body temperature of -2 to +2°C. Wet cooling allows for the fusion of water. Under these conditions, and if the capture is not very stressful, it is possible to prolong the duration of rigor mortis.
Freezing
Freezing is performed on whole fish or portions. Rapid techniques are used, either by contact or cooling tunnels. Storage should be done at temperatures below -18°C, with little ventilation and high humidity. To prevent fat oxidation and dryness, the surface is protected by spraying with water or packing in airtight material. Storage that is too long causes desiccation, rancidity, and yellowing or browning of the musculature.