1 / 34

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

anatola
Download Presentation

What Happens to Fish as it Freezes?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. What Happens to Fish as it Freezes?

  2. Nature of Raw Material • Fish/Shellfish Composition • Protein 15-25% • Fat 1-15% • Minerals 1-2% • Water 65-80%

  3. Water in Fish • Free – In Muscle • Transport – Dissolved Minerals • Bound –Attached to Proteins

  4. Freezing • Change State of Water • Liquid to Solid • Proteins aren’t changed • Fats aren’t changed • Minerals aren’t changed

  5. Freezing - Two Stages To Consider • Freezing Process • Cold Storage

  6. Freezing Process • What Occurs -Three Stages • First - Chilling/Removing Heat to the Transition Temperature

  7. Freezing Process • Second - Phase Change - Liquid to Solid - Over a Temperature Range – Fairly Complex • Third – Final Temperature Drop to Surroundings

  8. Freezing Curve

  9. Phase Change Happenings • As Temp Decreases Through “Critical” Zone • Pure Water Freezes in Crystals Starting Around 28F

  10. Phase Change Happenings • Salt/Solute Concentration Increases • Amount of Unfrozen Water Left

  11. Unfrozen Water

  12. Ice Crystals • Small Crystals - Fast Freezing • Large Crystals - Slow Freezing • Through the Phase Transition Zone

  13. Ice Crystal Size

  14. Freezing Time • Freezing Time - What is Fast? • Hours Vs. Days • Inches Per Hour

  15. Final Core Temp • Final Temperatures - What is Best? • -20F • -40F

  16. Other Things Happening During Freezing • Increased Enzyme Activity in Transition Zone • Glassy State Conditions

  17. Glassy State • Occurs Around 5 to 10 F • In Pockets – Hi Concentration of Salts/Enzymes • Ice Crystals Dissolve

  18. Glassy State • Ice Recrystallizes in Larger Chunks • Quality Changes • Avoid this Region

  19. Other Things Happening During Freezing • Moisture Loss in Freezing • Freezing in Rigor • Visual Quality Concerns

  20. Moisture Loss in Freezing • Depending on System, Can Lose Water From Surface • Sometimes Up to 1% or 2%

  21. Freezing in Rigor • Stiffening of the salmon muscle shortly after death • May last several hours to days depending on temperature

  22. Freezing in Rigor • Don't process/handle fish in rigor • Gaping, Drip Loss and Toughness

  23. Cold Storage • Severe Conditions • Dry Air • Temperature Fluctuations

  24. Cold Storage • Glassy State Deterioration • Freezer Burn • Protection

  25. Quality Changes • Moisture Migration and Recrystallization • Hydrolytic Enzyme Activity • Protein Denaturation

  26. Moisture Migration and Recrystallization • Freezer Burn • Temperature Fluctuations – Limit Shelf Life

  27. Quality Changes • Fat Oxidation • Microbial Changes

  28. Minimizing Quality Losses • Cryoprotectants - Glazing • Antioxidants

  29. Glazing • Options for Glaze • Salt • Sugar • Antioxidants

  30. Glazing • Glaze Water Temperature • How Much Glaze? • Cold Storage Effects

  31. Minimizing Quality Losses • Packaging • Bleeding

  32. Packaging • Critical Aspect of Shelf Life • As Much Protection As You Can Afford • Plastics/Boxes/Vac Pack

  33. Shelf Life • Time of Acceptable Quality • Limiting Factor is Often Fat Oxidation • Also Texture Changes

  34. Shelf Life • Depends on • Water Content • Fat Content • Packaging • Storage Temperature

More Related