seafood

a look into the chemistry of seafood

Seafood Consumption

  • Fish + Shellfish
  • Sources of all seafood consumed in the US
    • 6% Domestic Farmed
    • 9% Domestic Wild Fisheries
    • 38% Imported Wild Fisheries
    • 47% Imported Farmed
  • The United States consumed an estimated 22.13 KG per capita of seafood in 2019.

Classification of Fish and Shellfish

  • There is such a large variety of creatures that are harvested from the water, so it is hard to classify them using only one set of criteria
    • Vertebrates & Invertebrates
    • Salt water & Fresh water
    • Lean & Fat

Vertebrate or Invertebrate

  • Divides water animals according to the presence or absence of a backbone
  • Vertebrate
    • Finfish have fins and internal skeletons and obtain oxygen from water
    • Sea mammals obtain oxygen from air and not water
  • Invertebrate or shellfish
    • Crustaceans have a segmented body
    • Mollusks
      • Univalve (one shell)
      • Bivalve (two shells hinged together)
      • Cephalopods (head and tentacles like squid, they appear different but are physiologically the same)
      • Good sources of carbohydrates

Salt or Freshwater

  • Saltwater fish
    • Majority of fish eaten in US come from salt water
    • More distinct flavor than freshwater
    • Halibut, flounder, haddock, red snapper, cod, salmon, striped bass, swordfish, shark, tuna
  • Freshwater fish
    • Catfish, perch, pike, trout

Lean or Fat

  • Fish generally have less fat than other meats
  • Higher fat fish
    • Salmon, mackerel, lake trout, tuna, butterfish, whitefish, herring
  • The American Heart Association recommends consuming at least 250mg of EPA and DHA fatty acids per day or 1.7 grams per week in order to gain health benefits.

Structure of Finfish

  • Tenderness is a quality that all fish share
  • 3 factors contribute to its tenderness
    • Collagen
      • 3% content - small amount when compared to meat and poultry (15%)
    • Amino Acid Content
      • Less hydroxyproline in its connective tissue
      • The collagen that is present breaks down at a lower temperature
    • Unique Muscle Structure
      • Fish muscles are shorter and are arranged in sheets
      • Muscles are layered and not bundled
      • Each segment or sheet is called a myotome
      • Contributes to the characteristic flakiness and tenderness
    • Myotomes
      • Layers of short fibers in fish muscle
      • Myotomes are separated by large sheets of thin connective tissue called myocommata
      • Myocommata turns into a soft gel by heat

Pigments in Finfish

  • White, pink, or red (or a combination)
  • Darker pigment
    • Due to the slow-twitch muscle fibers from endurance swimming
    • Higher fatty content darkens flesh color from fatty fish like mackerel and tuna
      • Higher myoglobin concentration leads to quicker rancidity. The iron in myoglobin accelerates the oxidation of fat in the muscle.
  • Lighter pigment
    • Due to the fast-twitch muscle fibers which are designed for quick short bursts of swimming

Mercury in Fish

  • Nearly all fish and shellfish contain traces of mercury (Hg)
  • Mercury makes its way into water and is taken up by fish
  • Larger fish have higher levels of mercury because every time they eat a small fish, they add mercury to their flesh
  • Some fish and shellfish have higher levels of mercury that may harm unborn babies or children's developing nervous system
  • Fish that are lower in mercury are:
    • Shrimp, canned light tuna, salmon, pollock, catfish, tilapia, crab, oysters, scallops, squid

Fish & Shellfish Inspection

  • The Department of Commerce's National Marine Fisheries Service is responsible for the inspection program
  • Based on wholesomeness of fish and the sanitary conditions of the processing plant
  • Inspection of finfish is voluntary and paid by the processor (unlike the inspection of meat and poultry)
  • Voluntary Quality Grading
    • Only inspected finfish are graded
    • Grading is voluntary
    • Based on appearance, texture, uniformity, good flavor, fresh odor, and an absence of defects
  • Shellfish can carry toxins from consuming poisonous plankton or algae
    • These toxins contain no color or odor and are not destroyed by cooking or freezing
  • Only shellfish harvested from certified water that have been tested to be free of excessive levels of microorganisms can be sold for consumption
  • Shucked shellfish must be tagged with a “sell by date” or a “date shucked”
  • Restaurants and shops must keep the seafood tags of all seafood for 90 days after consumption

Aquaculture

  • Aquaculture is the farming of aquatic species.
  • Submerged Cages and Net Pens
    • Used to farm finfish in the ocean
  • Lines
    • Used to farm seaweed and bivalves, like mussels, in the ocean
  • Bottom culture
    • Used to farm seaweed and bivalves, like oysters, in shallow coastal areas
  • Ponds and Tanks
    • Used to farm finfish and shrimp on land, coastal, or freshwater areas

Salmon Color

  • Caused by:
    • Orange Pigment = astaxanthin
    • Without this pigment, salmon flesh would be white with blush-like spots on it
  • Salmon has this pigment and not others
    • Salmon retains pigment in their muscles whereas other seafood do not
  • There is variation due to the quantity of astaxanthin-rich food in the salmon's diet and how well the fish is able to metabolize the pigment

Purchasing Finfish

  • Forms of finfish:
    • Whole: Entirely intact
    • Drawn: Whole with entrails removed
    • Dressed: Head, tail, fins, and scales have been removed in addition to the entrails
    • Steaks: Cut from dressed fish at a 90 degree angle
    • Fillets: Cut lengthwise to avoid bones
    • Sticks: Uniform portions cut from fillets or steaks; Can also be made from minced fish

Processed Finfish

  • Fabricated fish
    • Examples are fish sticks, fish cakes, nuggets, and simulated fillets
    • Uses less popular species
    • Deboned, ground, seasoned, shaped
  • Surimi (Imitation crab meat)
    • Fished that is skinned, deboned, minced, washed, strained, and shaped into small pieces to resemble crab, shrimp, or scallops

Spoilage

  • Spoilage Factors
    • Proteolic enzymes
      • Breakdown muscle proteins to amino acids
      • Amino acids become food for bacteria capable of turning histadine to histamine
    • Natural toxins
    • Contaminants
  • Bacterial enzymes
    • Breaks down amino acids and elevates levels of histamine (toxin)
    • Consumption of high amounts of histamine leads to scombroid fish poisoning (scombrotoxism)
      • Fish like Tuna, Mahi-mahi, and Bluefish are especially susceptible to this if not chilled properly
  • Doesn't change the smell or taste of the fish

Storing Fish for Freshness

  • Store under very cold temperatures
    • Lower temp to below 40F because bacteria carried by raw fish multiply rapidly above that temperature
    • You can use ice packs in a refrigerator to decrease temps to 32F, allowing you to keep fish for up to 3 days with that method
  • Store in a single layer
    • Stacking fish produces a bacteria-friendly environment because it would increase exposure to each other's moisture
  • Cover to prevent over-drying
    • Air in fridges are dry and you don't want to have too much dryness as that will affect the juiciness of the fish
  • Keep fish dry
    • Bacteria thrives in moist conditions
    • Pat down the fish with a paper towel in order to remove the excess moisture

SOME SEAFOOD-BASED RECIPES

Tuna Mayo Deopbap

Shrimp Curry

Crab Fried Rice

XO Shrimp Noodles

Garlic Butter Salmon

info from NYU