FISH
Guidelines for Preparing Fish
Fish Cooking Methods
Fish can be cooked whole or filleted.
Filleting a Whole Fish
Scraping Scales: Scrape off the scales using the back of a knife.
Removing Head and Fins: Cut off the head and fins.
Gutting the Fish: Cut the underside of the fish to remove the intestines.
Washing the Cavity: Rinse the cavity under running water.
Fish Preparation Methods:
Fillets: Long, thin pieces of flesh cut along the length of the fish on either side of the bone (both round and flat fish).
Steaks or Cutlets: Large slices created by cutting vertically through the round of fish (round fish only).
Suitable Methods for Cooking Fish
Baking: Example is cod.
Barbecuing: Example is trout.
Frying: Example is hake.
Poaching: Example is salmon.
Grilling: Example is tuna.
Stewing: Example is monkfish.
Microwaving: Example is salmon.
Steaming: Example is halibut.
Guidelines for Cooking Fish
Choosing Cooking Methods: Select appropriate cooking methods suited to the type of fish.
Example: Monkfish is suitable for slow cooking methods due to its firm texture.
Avoid Overcooking: Overcooking fish can make it tough, rubbery, and difficult to digest.
Effects of Cooking on Fish
Protein Coagulation: Proteins coagulate between 40-50°C, leading to fish shrinking.
Color Change: The fish changes from translucent to opaque when cooked.
Vitamin Loss: Some B-group vitamins are lost because they are not heat stable; others dissolve into the cooking liquid.
Bacteria Destruction: Cooking destroys bacteria present in fish.
Flavor Development: Flavor develops as extractives are released from fish fibers.
Collagen Conversion: Collagen converts to gelatin, enhancing fish digestibility as fibers loosen and fall apart.
Fish Processing
Freezing
Process: Fish can be frozen through commercial blast freezing at -30°C or home freezing at -25°C.
Effects:
Microorganisms are inactivated.
No impact on color, flavor, or texture, but B-group vitamins and extractives may be lost during thawing (drip loss).
Freezer burn can occur if packaging is damaged.
Oxidative rancidity and enzyme deterioration may occur if stored too long.
Examples of Fish: Cod, Salmon, Fish products (e.g., fish fingers).
Canning
Process: Fish is placed in sterile cans, sealed, and heated to high temperatures.
Canned mediums: Fish may be canned in oil, brine, spring water, or sauce (like tomato sauce).
Effects:
Changes in color, flavor, and texture occur.
Loss of B-group vitamins, particularly B1 (thiamine).
Microorganisms and enzymes destroyed.
Canned fish provides calcium as the canning process softens the bones for consumption.
Vitamins A and D are present if canned in oil.
Caloric and fat content increase if canned in oil or sauce.
Examples of Canned Fish: Tinned mackerel, Tinned tuna, Tinned salmon.
Smoking
Process: Fish is placed in brine or rubbed in salt for flavor and preservation, then smoked via cold or hot smoking.
Cold Smoking:
Fish is subjected to smoke from wood chips (temperature not exceeding 27°C).
Requires cooking before consumption, except for salmon and trout due to preventative chemicals (creosote and formaldehyde) that inhibit organism growth.
Hot Smoking:
Similar to cold smoking but temperature increases to about 80°C.
Fish requires no further cooking.
Effects of Smoking:
Color is changed (e.g., white fish can appear light yellow or brown).
Flavor becomes distinctive and smoky.
Salt content increases.
Examples of Smoked Fish: Haddock, Cod, Salmon.
Fish Products
Processed fish products are made from leftover parts of fish after cuts (like fillets or cutlets) are removed.
Fish Cakes:
Made from minced fish, potato, herbs, and seasoning; shaped into rounds, coated in breadcrumbs, fried briefly, and frozen.
Contains 35-45% fish.
Fish Fingers:
Made from blocks of frozen filleted white fish (e.g., cod), cut into fingers, dipped in batter or breadcrumbs, and refrozen.
Contains 50-70% fish.
Fish Extractives:
E.g., fish stock cubes made from dried fish juice extractives, mixed with cornflour, salt, and flavor enhancers.
Guidelines for Buying Fish
Retail Source: Buy from a retailer with a clean fish counter following strict food hygiene safety policies (HACCP).
Use-By Dates: Check the use-by date on packaged fish.
Quality Indicators:
Fish should have firm, elastic flesh.
Skin should be shiny, moist, unbroken, and slime-free; slime indicates bacteria.
Whole fish should have bright, bulging eyes and bright red gills.
Cuts of fish should have firm, transparent flesh, with no bruising.
Shellfish should feel heavy and have closed shells (indicates freshness); open shells mean they are dead and inedible.
Crustaceans must be alive to minimize food poisoning risk due to spoilage.
Odor: Fish should smell of the sea; unpleasant smells suggest bacterial growth.
Smoky fish should have a fresh aroma.
Shopping Order: Buy fish towards the end of your shopping trip to minimize time at room temperature.
Guidelines for Storing Fish
Refrigeration: Store fish in a fridge at 4°C; room temperature accelerates bacterial growth, increasing spoilage.
If pre-packaged, keep in original packaging on the bottom shelf.
If loose, rinse under cold water, place on a plate/container (to collect juices), cover, and refrigerate.
Strong Aromas: Store strong-smelling fish away from other foods to prevent flavor absorption (e.g., milk and butter).
Storage Duration: Use fish within 24 hours, as it spoils quickly.
For freezing fresh fish, do it at -25°C on the day of purchase.
Causes of Fish Spoilage
Oxidative Rancidity: Oils in oily fish react with oxygen, causing rancidity, particularly with unsaturated fats.
Enzymes: Natural enzymes in fish lead to deterioration; refrigeration or icing slows this.
Bacteria: After fish are caught, glycogen stores are depleted, preventing conversion to lactic acid for preservation, resulting in rapid bacterial deterioration and strong-smelling trimethylamine.
Nutritional Value of Fish
Categories of Fish
White Fish: Round and flat types such as cod, plaice, whiting, monkfish.
Oily Fish: Round categories including mackerel, tuna, herring, salmon.
Shellfish:
Molluscs: E.g., mussels, oysters.
Crustaceans: E.g., lobster, crab.
Average Nutritional Composition of Fish
Nutrients in Different Types of Fish
White Fish
Proteins: 17.5%
Fat: 0.5%
Carbohydrates: 0%
Vitamins: A, B group, D
Minerals: Zinc, potassium, iodine
Water: 80.5%
Oily Fish
Proteins: 18%
Fat: 16%
Carbohydrates: 0%
Vitamins: B group
Minerals: Zinc, potassium, phosphorus, fluorine, iodine
Water: 65%
Shellfish
Proteins: 15-18%
Fat: 0%
Carbohydrates: 0%
Vitamins: A, B group, C
Minerals: Iron, zinc, potassium, phosphorus, fluorine, iodine
Water: 78%
Nutritional Contributions of Fish
Proteins: High biological value (HBV) proteins; main proteins are myosin and actin in myomeres, and collagen in connective tissues.
Fats: Oily fish are rich in polyunsaturated fats, especially omega-3 fatty acids (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)).
White fish has no fat.
Carbohydrates: Generally absent; glycogen converts to lactic acid.
Vitamins: Rich in B-group vitamins; some shellfish provide vitamins A and C.
Minerals: Contains essential minerals; canned fish has calcium due to edible bones.
Water: Higher water content typically correlates with lower fat content.
Dietetic Value of Fish
Fish provides easily digestible HBV protein essential for growth and repair—valuable in children's, teenagers', and pregnant women's diets.
White fish, being low in fat, is ideal for calorie-controlled diets.
Tuna intake is advised to be reduced during pregnancy due to potential mercury contamination affecting fetal development.
Oily fish benefits heart health by increasing HDL cholesterol, thus lowering overall cholesterol levels.
Variety in types and forms of fish enhances diet and caters to diverse tastes.
Fish's fast cooking time is energy efficient.
Balance diet by pairing fish with carbohydrate-rich foods due to its low carbohydrate content.