Sanitation and management of aquatic products and aquatic products
作者：admin 点击次数：137 发布时间：2025-06-07
microbial contamination of aquatic products and aquatic products
Aquatic products include many groups of the animal kingdom, such as molluscs (mussels, snails, etc.), arthropods (shrimp crabs, etc.), echinoderms (sea urchins, sea cucumbers, etc.), chordates (fish, hairtail, etc.), and the most common raw materials used in the food processing industry are ichthyidae. Aquatic products, represented by fish, are one of the best sources of high-quality protein, unsaturated fatty acids, important minerals and B vitamins in the human diet. Compared with other animal foods, they are easy to digest and absorb, so they have high edible value. Aquatic products, especially fresh and mildly processed aquatic products, are a type of food that is very perishable because they have a moderate pH, high moisture content and are rich in nutrients, which are ideal for the growth of microorganisms. (1) Microorganisms that pollute aquatic products
Whether it is freshwater fish or marine fish, there are a large number of microorganisms in the water environment in which they live. Although the tissues of living fish are sterile, there are a certain amount of microorganisms in the aquatic environment on their body surface and digestive tract. The types of bacteria are the same as those found in the water environment where fish live.
1. Spoilage bacteria
Bacteria that are common in marine fish and can cause spoilage are Pseudomonaspora spp., Achromobacter spp., Flavobacterium spp., and Morsella spp. In addition to the above-mentioned bacteria, there are also bacteria of the genus Alkalogenic Bacillus and B. brevid. Most of these microorganisms grow and develop quickly at room temperature, causing spoilage of fish.
2. There are many microorganisms carried in the body and surface of pathogenic aquatic products, and pathogenic bacteria are the most harmful. From the primary contamination are Vibrio parahaemolyticus, Vibrio cholerae, Clostridium botulinum, Listeriella, Aeromonas, Orthomonas, etc. Vibrio parahaemolyticus and Vibrio cholerae are mainly found in coastal or bay waters in the temperate tropics, while other bacteria are widely distributed in waters around the world, and there are many opportunities to contaminate aquatic products. Salmonella, Escherichia coli, Shigella, Staphylococcus aureus, etc., which originate from the intestines, body surface and respiratory tract of humans and animals, and contaminate aquatic products by polluting the environment through excrement and secretions or by carriers coming into contact with food.
3. Viruses
Viruses that are easy to contaminate aquatic products include hepatitis A virus, norovirus, centella asiatica virus, cup-in-cup virus, astrovirus, etc. These viruses mainly originate from the intestines of sick people, sick animals or carriers of the virus, contaminate water bodies or contaminate aquatic products after contact with hands. The vast majority of all reported viral infections related to aquatic products are caused by the consumption of raw or inadequately heated shellfish. Filter-feeding shellfish have a large draught, resulting in the enrichment of viruses in shellfish that is much higher than in the surrounding water bodies.
(2) The process of spoilage of fresh fish
Fish that die after harvesting will deteriorate quickly due to the microorganisms present in the body and the microorganisms contaminated after fishing. First of all, due to the action of bacteria and enzymes in the fish body, the mucus protein on the body surface of the fish can make the surface of the fish appear turbid and lose its luster, the epidermal tissue changes from hard to loose, and the scales fall off. At the same time, the bacteria in the digestive tract also multiply rapidly, causing the digestive tract tissues to ulcerate, and the bacteria then enter the inner cavity of the mermaid, causing damage to the fish body tissues from the inside. At this point, the proteins on the surface and inside of the fish body are decomposed into amino acids under the action of enzymes and microorganisms, and the phospholipids rich in trimethylamine are reduced to release trimethylamine, giving the fish body a strong fishy smell. All of these changes are the first signs of spoilage of fresh fish. In the second stage of deterioration, bacteria can quickly decompose amino acids and produce volatile substances such as indole, ammonia, odoroids, hydrogen sulfide, etc., no matter how many bacteria are carried in the fish body when it is fresh, when the senses can perceive the rancid smell, the number of bacteria has generally reached the level of 1x10 per g. In addition, the alkalinity of the tissue increases, the pH can rise to 7~8, and the amount of volatile amino nitrogen can reach 30mg100g of food.