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Preservation of Seafoods FSN 261 Spring 2011

Preservation of Seafoods FSN 261 Spring 2011. Chuck Crapo Seafood Technology Specialist. Objectives of the next three lectures. Know the major methods of preservation Effects of heating, freezing and refrigeration on safety, quality and shelf-life

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Preservation of Seafoods FSN 261 Spring 2011

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  1. Preservation of SeafoodsFSN 261 Spring 2011 Chuck Crapo Seafood Technology Specialist

  2. Objectives of the next threelectures • Know the major methods of preservation • Effects of heating, freezing and refrigeration on safety, quality and shelf-life • Effects drying and other methods on safety, quality and shelf-life • Other processing methods

  3. Fight against deterioration • Microorganisms • Chemical reactions • Non-enzymatic • Enzymatic • Unique properties of seafoods

  4. Economic and Safety importance • Economic (shelf-life) • Spoilage organisms • Enzymes • Food Safety • Pathogenic organisms • Toxins, and other chemicals

  5. Food Preservation • Chemically • Additives : sugar, salt, acids • Preservatives • Physically • Increase Energy Level • Heating, Ultra-high pressure, etc. • Decrease Energy Level • Freezing, chilling, refrigeration • Decrease Water Content • Concentration, dehydration, smoking • Packaging • Biologically • Fermentation • Genetic Engineering

  6. Objectives (1) • Increasing the energy • Heating • Irradiation • Ultra-high pressure • Decreasing the energy • Chilling • Freezing • Ultra-cooling / supercooling

  7. Effects of heat on microorganisms • Lethal range. • Differences between spores and vegetative cells • Differences between various organisms

  8. Lethal Temperature Range • Different organisms Spores Vegetative Cells Temperature 60 C = 140 F 100 C = 212 F

  9. Levels of heating • Pasteurization • Mild Heat Treatment • Below Boiling • Sterilization • Serious Heat Treatment • Above Boiling (pressure)

  10. Pasteurization • Definition: “Elimination of vegetative pathogenic micro-organisms at the slowest heating point.”

  11. Examples • Pasteurized crab meat: • Will not make you sick, but can spoil if not refrigerated. • Cooked shrimp: Spores are not dead: under certain conditions they can germinate and cause trouble.

  12. Commercial Sterility • Definition Under “normal” storage conditions, the commercially sterile food (can/jar/pouch) will not spoil. The product must be safe But it can spoil under unusual conditions What is “normal” storage?

  13. Effects of heat on fish • Denaturation of the proteins • Loss in water-holding capacity • Change in texture • Change in color • Development of flavor / volatiles • Acceleration of chemical reactions

  14. Denaturation

  15. Canning • Seal the food in a can/jar/pouch • Heat the can to sterilize its contents • Now the container will last for years at room temperature, and its contents will still be nutritious

  16. Salmon can vs. pouch

  17. Statistics on canning

  18. Refrigeration / FreezingDefinitions • Chilling: Temperatures between 50oF and slightly above freezing point. • Freezing: From slightly below freezing point to at least 0oF (preferably -20F).

  19. Refrigeration • Biochemical reactions and microorganisms slow-down or stop at low temperatures. • Even under the best refrigeration conditions, seafood has a limited shelf-life.

  20. Changes during refrigeration Lipid oxidation Protein denaturation Vitamin loss, Off-flavors Depends on storage conditions, on the tissue and on species.

  21. Refrigeration and Shelf Life

  22. Freezing • Freezing retards: ‑ Growth of microorganisms ‑ Rate of chemical reactions ‑ Enzyme activity ‑ Moisture loss

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

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

  25. Freezing Curve

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

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

  28. Unfrozen Water

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

  30. Ice Crystal Size

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

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

  33. Freezing and Shelf Life

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