Preservation of Seafoods

FSN 261 Spring 2011

Chuck CrapoSeafood 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

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5

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

15

16

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

•

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?

51