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What Happens to Fish as it Freezes? - PowerPoint PPT Presentation


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What Happens to Fish as it Freezes?. Nature of Raw Material. Fish/Shellfish Composition Protein 15-25% Fat 1-15% Minerals 1-2% Water 65-80%. Water in Fish. Free – In Muscle Transport – Dissolved Minerals Bound –Attached to Proteins. Freezing. Change State of Water

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Presentation Transcript
nature of raw material
Nature of Raw Material
  • Fish/Shellfish Composition
  • Protein 15-25%
  • Fat 1-15%
  • Minerals 1-2%
  • Water 65-80%
water in fish
Water in Fish
  • Free – In Muscle
  • Transport – Dissolved Minerals
  • Bound –Attached to Proteins
freezing
Freezing
  • Change State of Water
  • Liquid to Solid
  • Proteins aren’t changed
  • Fats aren’t changed
  • Minerals aren’t changed
freezing two stages to consider
Freezing - Two Stages To Consider
  • Freezing Process
  • Cold Storage
freezing process
Freezing Process
  • What Occurs -Three Stages
  • First - Chilling/Removing Heat to the Transition Temperature
freezing process7
Freezing Process
  • Second - Phase Change - Liquid to Solid - Over a Temperature Range – Fairly Complex
  • Third – Final Temperature Drop to Surroundings
phase change happenings
Phase Change Happenings
  • As Temp Decreases Through “Critical” Zone
  • Pure Water Freezes in Crystals Starting Around 28F
phase change happenings10
Phase Change Happenings
  • Salt/Solute Concentration Increases
  • Amount of Unfrozen Water Left
ice crystals
Ice Crystals
  • Small Crystals - Fast Freezing
  • Large Crystals - Slow Freezing
  • Through the Phase Transition Zone
freezing time
Freezing Time
  • Freezing Time - What is Fast?
  • Hours Vs. Days
  • Inches Per Hour
final core temp
Final Core Temp
  • Final Temperatures - What is Best?
  • -20F
  • -40F
other things happening during freezing
Other Things Happening During Freezing
  • Increased Enzyme Activity in Transition Zone
  • Glassy State Conditions
glassy state
Glassy State
  • Occurs Around 5 to 10 F
  • In Pockets – Hi Concentration of Salts/Enzymes
  • Ice Crystals Dissolve
glassy state18
Glassy State
  • Ice Recrystallizes in Larger Chunks
  • Quality Changes
  • Avoid this Region
other things happening during freezing19
Other Things Happening During Freezing
  • Moisture Loss in Freezing
  • Freezing in Rigor
  • Visual Quality Concerns
moisture loss in freezing
Moisture Loss in Freezing
  • Depending on System, Can Lose Water From Surface
  • Sometimes Up to 1% or 2%
freezing in rigor
Freezing in Rigor
  • Stiffening of the salmon muscle shortly after death
  • May last several hours to days depending on temperature
freezing in rigor22
Freezing in Rigor
  • Don't process/handle fish in rigor
  • Gaping, Drip Loss and Toughness
cold storage
Cold Storage
  • Severe Conditions
  • Dry Air
  • Temperature Fluctuations
cold storage24
Cold Storage
  • Glassy State Deterioration
  • Freezer Burn
  • Protection
quality changes
Quality Changes
  • Moisture Migration and Recrystallization
  • Hydrolytic Enzyme Activity
  • Protein Denaturation
moisture migration and recrystallization
Moisture Migration and Recrystallization
  • Freezer Burn
  • Temperature Fluctuations – Limit Shelf Life
quality changes27
Quality Changes
  • Fat Oxidation
  • Microbial Changes
minimizing quality losses
Minimizing Quality Losses
  • Cryoprotectants - Glazing
  • Antioxidants
glazing
Glazing
  • Options for Glaze
  • Salt
  • Sugar
  • Antioxidants
glazing30
Glazing
  • Glaze Water Temperature
  • How Much Glaze?
  • Cold Storage Effects
minimizing quality losses31
Minimizing Quality Losses
  • Packaging
  • Bleeding
packaging
Packaging
  • Critical Aspect of Shelf Life
  • As Much Protection As You Can Afford
  • Plastics/Boxes/Vac Pack
shelf life
Shelf Life
  • Time of Acceptable Quality
  • Limiting Factor is Often Fat Oxidation
  • Also Texture Changes
shelf life34
Shelf Life
  • Depends on
  • Water Content
  • Fat Content
  • Packaging
  • Storage Temperature