Preservation of Seafoods FSN 261 Spring 2011
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Transcript of Preservation of Seafoods FSN 261 Spring 2011
Preservation of Seafoods
FSN 261 Spring 2011
Chuck CrapoSeafood Technology
Specialist
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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
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Economic and Safety importance
• Economic (shelf-life)– Spoilage organisms– Enzymes
• Food Safety – Pathogenic organisms– Toxins, and other chemicals
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Food Preservation
ChemicallyAdditives : sugar, salt, acidsPreservatives
PhysicallyIncrease Energy Level
Heating, Ultra-high pressure, etc.Decrease Energy Level
Freezing, chilling, refrigerationDecrease Water Content
Concentration, dehydration, smokingPackaging
BiologicallyFermentationGenetic Engineering
Objectives (1)• Increasing the energy
– Heating – Irradiation– Ultra-high pressure
• Decreasing the energy– Chilling– Freezing– Ultra-cooling / supercooling
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Effects of heat on microorganisms
• Lethal range.
• Differences between spores and vegetative cells
• Differences between various organisms
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Lethal Temperature Range• Different organisms
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VegetativeCells
Spores
60 C = 140 F 100 C = 212 FTem
pera
ture
Levels of heating• Pasteurization
– Mild Heat Treatment– Below Boiling
• Sterilization– Serious Heat Treatment– Above Boiling (pressure)
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Pasteurization• Definition:“Elimination of vegetative
pathogenic micro-organisms at the slowest heating point.”
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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.
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Commercial Sterility• DefinitionUnder “normal” storage conditions,
the commercially sterile food (can/jar/pouch) will not spoil.
The product must be safeBut 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
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Denaturation
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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
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Typical retorting times of salmon (min)
115.6 C
121.1 C
50
35
70
55
100
85
230
200
Diam. (mm)
Height (mm)
74
35
84
46.5
74
118.5
154
109.5
Salmon can vs. pouch
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Statistics on canning
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2002 2003 2004 2005 2006 2007 2008Year
0
5
10
15
20
Pou
nds
edib
le m
eat
U.S. Annual per capita consumption of seafood
Total
Fresh and frozen
Canned
Cured
2002 2003 2004 2005 2006 2007 2008year
0
1
2
3
4
5
Pou
nds
edib
le m
eat
U.S. Annual Per Capita Consumption of Canned Seafood
OtherShellfishSalmon
Tuna
Total
Sardines
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Refrigeration / FreezingDefinitions
• Chilling: Temperatures between 50oF and slightly above freezing point.
• Freezing: From slightly below freezing point to at least 0oF (preferably -20F).
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Refrigeration• Biochemical reactions and
microorganisms slow-down or stop at low temperatures.
• Even under the best refrigeration conditions, seafood has a limited shelf-life.
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Changes during refrigeration
Lipid oxidationProtein denaturationVitamin loss, Off-flavors
Depends on storage conditions, on the tissue and on species.
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Refrigeration and Shelf Life
Freezing• Freezing retards:
‑ Growth of microorganisms‑ Rate of chemical reactions‑ Enzyme activity‑ Moisture loss
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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
01 02 03 04 05 06 07 08 09 0
1 0 0
3 2 3 0 . 2 2 8 . 4 2 6 . 6 2 4 . 8 2 3 1 4 - 4 - 2 2 - 4 0T i m e
% U
nfr
oze
n W
ate
r
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?
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