What Happens to Fish as it Freezes?

•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
•Liquid to Solid
•Proteins aren’t changed
•Fats aren’t changed
•Minerals aren’t changed
•Freezing – Two Stages To Consider
•Freezing Process
•Cold Storage
•Freezing Process
•What Occurs -Three Stages
•First – Chilling/Removing Heat to the Transition Temperature
•Freezing Process
•Second – Phase Change – Liquid to Solid – Over a Temperature Range – Fairly Complex
•Third – Final Temperature Drop to Surroundings
•Freezing Curve
•Phase Change Happenings
•As Temp Decreases Through “Critical” Zone
•Pure Water Freezes in Crystals Starting Around 28F
•Phase Change Happenings
•Salt/Solute Concentration Increases
•Amount of Unfrozen Water Left
•Unfrozen Water
•Ice Crystals
•Small Crystals – Fast Freezing
•Large Crystals – Slow Freezing
•Through the Phase Transition Zone
•Ice Crystal Size
•Freezing Time
•Freezing Time – What is Fast?
•Hours Vs. Days
•Inches Per Hour
•Final Core Temp
•Final Temperatures – What is Best?
•-20F
•-40F
•Other Things Happening During Freezing
•Increased Enzyme Activity in Transition Zone
•Glassy State Conditions
•Glassy State
•Occurs Around 5 to 10 F
•In Pockets – Hi Concentration of Salts/Enzymes
•Ice Crystals Dissolve
•Glassy State
•Ice Recrystallizes in Larger Chunks
•Quality Changes
•Avoid this Region
•Other Things Happening During Freezing
•Moisture Loss in Freezing
•Freezing in Rigor
•Visual Quality Concerns
•Moisture Loss in Freezing
•Depending on System, Can Lose Water From Surface
•Sometimes Up to 1% or 2%
•Freezing in Rigor
•Stiffening of the salmon muscle shortly after death
•May last several hours to days depending on temperature
•Freezing in Rigor
•Don’t process/handle fish in rigor
•Gaping, Drip Loss and Toughness
•Cold Storage
•Severe Conditions
•Dry Air
•Temperature Fluctuations
•Cold Storage
•Glassy State Deterioration
•Freezer Burn
•Protection
•Quality Changes
•Moisture Migration and Recrystallization
•Hydrolytic Enzyme Activity
•Protein Denaturation
•Moisture Migration and Recrystallization
•Freezer Burn
•Temperature Fluctuations – Limit Shelf Life
•Quality Changes
•Fat Oxidation
•Microbial Changes
•Minimizing Quality Losses
•Cryoprotectants – Glazing
•Antioxidants
•Glazing
•Options for Glaze
•Salt
•Sugar
•Antioxidants
•Glazing
•Glaze Water Temperature
•How Much Glaze?
•Cold Storage Effects
•Minimizing Quality Losses
•Packaging
•Bleeding
•Packaging
•Critical Aspect of Shelf Life
•As Much Protection As You Can Afford
•Plastics/Boxes/Vac Pack
•Shelf Life
•Time of Acceptable Quality
•Limiting Factor is Often Fat Oxidation
•Also Texture Changes
•Shelf Life
•Depends on
•Water Content
•Fat Content
•Packaging
•Storage Temperature

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