Preservation of Seafoods FSN 261 Spring 2011

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

17. Salmon can vs. pouch

18. Statistics on canning

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

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

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

32. Refrigeration and Shelf Life

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

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

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

42. Freezing Curve

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

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

45. Unfrozen Water

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

47. Ice Crystal Size

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

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

50. Freezing and Shelf Life