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Identification of aquatic products and their products (2)
31. Identification of Contaminated Fish, Rivers, and Lakes
Due to the impact of industrial wastewater discharge, fish can become contaminated and die, often ending up in the market for sale. Identifying contaminated fish involves checking several key aspects:
(1) Posture: Contaminated fish often show physical deformities, such as a small head and tail, or an abnormally shaped body with a soft belly, bent spine, and discolored scales (yellow, red, or blue).
(2) Eyes: The eyes of contaminated fish are usually cloudy, dull, or even bulging.
(3) Gills: The gills may appear pale or whitish, indicating poor health.
(4) Odor: Contaminated fish typically emit strong smells like ammonia, kerosene, or hydrogen sulfide, and lack the natural fishy odor.
32. Which Parts of the Pufferfish Contain Toxins?
The main toxic components in pufferfish are found in the ovaries and liver. Other parts, such as the kidneys, blood, eyes, gills, and skin, may also contain toxins. During winter and spring, the ovarian toxins are most concentrated. Even a small piece of this tissue can cause severe poisoning.
33. Which Parts of the Carp Contain Toxins?
Carp, also known as mackerel, contains black blood. After cutting the back, a blood line is visible. This line is toxic, and if not removed during washing, it can cause allergic reactions when cooked and eaten. If the fish has a soft, yellow abdomen, broken belly, or a pasty mouth, it is likely spoiled, and eating it may lead to swelling or illness.
34. Which Parts of the Carp Contain Toxins?
Also known as blue spot carp, these fish have tender meat and a garlic-like texture. However, their liver contains toxic substances and should be removed before cooking to avoid poisoning.
35. Which Parts of the Pond Fish Contain Toxins?
Pond fish, also called blue round or barb fish, are generally safe when fresh. However, if left for too long, histidine in the fish breaks down into toxic ammonia, leading to food poisoning.
36. Which Parts of the Carp Contain Toxins?
Also known as yubalang or beard fish, this freshwater species is rich in nutrients. When cleaning, the eggs must be removed, as they are toxic and inedible.
37. Which Parts of the Carp Contain Toxins?
Known as white peony or bitter chains, this common freshwater fish is popular due to its affordability. Its liver contains toxins, so it should be removed before consumption to prevent food poisoning.
38. Which Parts of the Catfish Contain Toxins?
Catfish from Qinghai Lake have poisonous viscera and eyes. These parts must be removed during cleaning to avoid poisoning.
39. Which Parts of the River Eel Contain Toxins?
River eels, also called cockroaches or white cockroaches, have toxic serum. Contact with wounds can cause inflammation or infection.
40. Why Can't You Eat Dead Stingrays?
Stingrays, also known as Astragalus, are high in histidine. After death, this compound converts into toxic histamine, causing food poisoning. Their blood is also toxic and can cause infections if it comes into contact with open wounds.
41. Why Can’t You Eat Dead Soft-Shell Turtles?
Soft-shell turtles, also called group fish, are nutritious but dangerous when dead. Histidine in their bodies breaks down into histamine, which can trigger severe allergic reactions, including shock. Dead turtles should never be consumed.
42. Sensory Identification of Freshness in Aquatic Products
To determine freshness, you can perform a boiled test. For slightly less fresh products, boiling them and observing the smell, taste, and soup can help identify spoilage. Fresh products will have a clear, pleasant aroma, while spoiled ones will smell foul or ammonia-like.
43. Rapid Test for Freshness of Aquatic Products
(1) pH Measurement: Fresh fish has a pH of 6.5–6.8; slightly spoiled fish has a pH of 6.9–7.0; and rotten fish has a pH above 7.1.
(2) Hydrogen Sulfide Test: A color change on filter paper indicates spoilage.
(3) Ammonia Test: Cloudiness in the test tube shows increasing spoilage.
44. Quality Identification of Kelp
Good quality kelp is dark brown or green-brown, thick, and free of roots. It has a slight white powder and few impurities. Poor-quality kelp is yellow-green and thin.
45. Quality Identification of Shark Fins
High-quality shark fins are large, dry, and smooth, with a slight sheen. Lower-quality fins are smaller and thinner.
46. Quality Identification of Bird’s Nest
Bird’s nests are classified into three levels. High-quality nests are white, transparent, and free of impurities. Lower-quality nests have more feathers and dirt.
47. Quality Identification of Dried Scallops
Dried scallops are made from the adductor muscle of shellfish. High-quality scallops are large, firm, and rich in protein.
48. Quality Identification of Dried Abalone
High-quality abalone is oval-shaped, with a complete form and no impurities. Poor-quality abalone is thin, dark, and lacks luster.
49. Quality Identification of Dried Squid
Top-grade dried squid is large, pink, and smooth. Lower grades are smaller and less vibrant.
50. Quality Identification of Dried Shrimp
Fresh shrimp are curved, with a bright color and no impurities. Spoiled shrimp are straight, dark, and have a salty taste.
51. Quality Identification of Dried Mussels
Dried mussels are graded by size. Top-grade mussels are large, uniform, and have a shiny appearance.
52. Quality Identification of Fish Maw
Fish maw, made from fish swim bladders, is valued for its texture. High-quality maw is thick, smooth, and free of discoloration.
53. Quality Identification of Fish Skin
High-quality fish skin is transparent, thick, and free of salt. Low-quality skin is dark, smelly, and brittle.
54. Quality Identification of Dried Oyster Stems
Dried oyster stems are graded based on size and shape. High-quality stems are large, golden, and free of impurities.
55. Color Changes in Dried Seafood
Dried seafood can turn red due to bacterial growth in humid conditions. Proper storage and packaging are essential to prevent this.
56. Flavor Changes in Dried Seafood
Long-term storage can cause fat oxidation, leading to bitterness and off-flavors. Proper cooling and storage help maintain quality.
57. Mold Prevention in Dried Seafood
Insects and mold are common issues. Regular cleaning, fumigation, and cold storage are effective prevention methods.
58. Principles of Sensory Identification and Consumption of Aquatic Products
Fresh aquatic products should be consumed immediately. Sub-fresh products should be sold quickly, and spoiled ones should be discarded.
59. Identification of Artificial vs. Natural Jellyfish
Artificial jellyfish is brittle and lacks elasticity, while natural jellyfish is firm and has a natural texture.
60. Identification of Fake Crab Meat
Fake crab meat often shows colored patterns under light, unlike real crab meat. This helps distinguish between genuine and fake products.
61. Identification of Cultured vs. Wild Shrimp
Wild shrimp have a better taste and texture than cultured shrimp. They also have a shorter, harder head compared to farmed shrimp.
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