Preservation of Seafoods FSN 261 Spring 2011 Chuck Crapo Seafood Technology Specialist 1

Objectives of the next three lectures 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 2

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

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

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

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

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

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

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

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

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. 11

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? 12

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 13

Denaturation 14

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 15

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Salmon can vs. pouch 17

Statistics on canning 18

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

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

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

Refrigeration and Shelf Life

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

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

Freezing and Shelf Life

Questions? 51