Seafood Quality

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Seafood Quality

• Chuck Crapo
• Marine Advisory Program
• Fishery Industrial Technology Center
• Kodiak

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Seafood Quality

• Quality is one of the most important aspects of
  seafood technology.
• Much of the effort of seafood science goes into
  the control of fish quality.
• But What Is Quality?

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Seafood Quality

• What is Quality?
• Production of a consistent seafood product that
  is acceptable to the marketplace.
• Many definitions for quality that are defined by
  buyer and seller.

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Types of Quality

• Intrinsic - factors that are inherent in the raw
  product and essentially uncontrollable
• Examples - Species
• Size
• Physiological Condition
• Parasites
• Composition

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Types of Quality

• Extrinsic - quality that is influenced by outside
  factors and controllable
• Examples - Handling
• Storage Conditions
• Processing Factors
• Delivery Times

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Muscle Anatomy

• Very simple --Consists of 2 bundles of muscle on
  each side of vertebrae. Separated into upper and
  lower masses.
• Muscle cells run longitudinally separated by
  sheets of connective tissue.

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Muscle Anatomy

• Also classified as light and dark.
• Dark (cruising) muscle -
• Light (sprinting) muscle -
• Muscle type affects keeping quality since the
  dark muscle is more susceptible to breakdown.

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Composition

• Water
• Protein
• Lipid (Fat)
• Ash
• Carbohydrates
• Non-Protein Nitrogen Compounds

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Role

• Water - major component, bound to the proteins
• Lipids - located in belly flaps and connective
  tissue. - long chain, unsaturated fatty acids
  highly susceptible to oxidation

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Role

• Proteins Structural-actin, myosin (70),
  Sarcoplasmic globulins, enzymes (20) Connective
  tissue - collagen (10)
• Non-Protein Nitrogen Compounds - Water soluble
  chemicals.
• Ammonia
• Trimethylamine oxide (TMAO)
• Amino Acids
• Nucleotides (ATP)

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Post Mortem Changes

• Organoleptic Changes - changes in appearance,
  odor texture and flavor
• Rigor Mortis
• Changes in Eating Quality

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Rigor Mortis

• Muscles are flexible and soft -pre-rigor.
• Muscles contract, become stiff and hard - state
  of 'rigor mortis'.
• Muscles relax and become flexible and soft again
  - post rigor.

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Rigor Mortis

• Complex reactions with ATP depletion and
  accumulation of lactic acid.
• High temperature rigor - failure of connective
  tissue.
• Quality effects - shrinking fillets, gaping,
  texture changes and excessive drip loss.

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Gaping
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Changes in Eating Quality

• Changes in flavor compounds autolytic/ bacterial
• Phase 1 - Very fresh fish typical odor and flavor
  with seaweedy, delicate flavor.
• Phase 2 - Loss of characteristic odor and flavor
  and neutral taste.
• Phase 3 - Early signs of spoilage with slight
  off-flavors such as sour, sickly sweet and
  bitter.
• Phase 4 - Spoiled and putrid

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Autolytic Changes

• Glycogen metabolized anaerobically to produce
  lactic acid until ATP is used.
• ATP degrades through a series of reactions to
  produce hypoxanthine.
• Protein changes less severe. Cathepsins slowly
  soften the tissue.

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Autolytic Changes

• Very active enzymes responsible for digesting
  feed such as pepsin and trypsin.
• After death, enzyme slowly solubilize the organs
  - stomach/intestines and then the muscle tissue
  of the belly.
• In heavily feeding fish, enzymes can be active
  enough to "eat" through the belly wall in a few
  hours causing belly burst or belly burn. Coho
  salmon and winter herring are examples.

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Bad
Good
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Bacterial Changes

• Bacteria outer surfaces of fish
• Skin - 102 to 107/cm2
• Gills - 103 to 109/cm2
• Intestines - 103 to 109/cm2
• Wide range reflects environment.

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Bacterial Changes

• Bacterial psychotrophs (cold loving)
• In live fish, muscles are sterile
• Growth occurs on gills, skin and gut.
• Punctures/breaks in the skin - bacteria invade
  the muscle.

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Softness
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Rancidity Changes

• oxidation of lipids
• auto oxidation
• lipid hydrolysis

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Rancidity

• Auto oxidation - incorporation of oxygen into
  fat. Several distinct stages of oxidation, each
  characterized by unique compounds - peroxides,
  ketones, aldehydes.
• Lipid hydrolysis - enzymatic action on lipids.
  Lipases found in viscera and bacteria. Produces
  free fatty acids that produce a soapy taste.

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Quality

• All these processes going on make seafood very
  perishable
• Controlling what is possible extends the quality,
  but we have limited shelf life anyway.

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