Quality and Safety of Channel Catfish (Ictalurus

punctatus) Affected by Production,

Harvest & Post-harvest Practices

Juan L. Silva, Taejo Kim and Youkai Lu

Muchas Gracias!

Oceanic InstituteAIP Workshop

Seafood Quality and AquacultureOctober 22-24, 2007

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CATFISH PRODUCTIONFARM TO PLATE

Pre-harvest Site selection Soil Water source Water quality management and controlMaintenance of various life stagesFeed quality and feeding regime/practicesFish health managementAnimal controlHuman hygiene and healthProper sanitation and sanitary conditionsChemical applications

Harvest & Post-harvestHarvest Live hauling

Receiving/HoldingStunningBeheading/bleedingTime to Ice/BrineChillingPackingMarinatingFreezing

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Catfish Quality and Safety

Spoilage– Off-color and off-

flavor– Enzymatic– Microbiological– Oxidative

Hazards– Chemical residues– Drugs– Microbiological– Metals

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Species, site selection & soil

SpeciesSite selection – floods, – soil, – animals

Soil – heavy metals,– chemicals

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Production practices

Stocking density

Environmental management

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Water source & water quality

Water source– pathogens, – chemical residues– Off-flavors

Water quality management and control– chemical residues– Off-flavors

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Greenish discolorationMay be the result of water quality, heme pigment changes due to iron or reducing agents, or other causes like too much blood in the muscle.Pink fillets may be the result of nitrites in the water, cure, or elsewhere.

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Feed quality and feeding regime

Feed quality – Protein– Antioxidants– Pigments– Pathogens/Toxins– Drugs

Feeding regime/practices– Season– Satiation

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Yellow pigmentation

• Usually the result of yellowpigments (asthaxanthins) in the feed or lagoon (yellow corn feed, algae), usually along fatty tissue

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Diseases, chemicals, animals

Fish health management– Diseases– Chemicals & drugs

Chemical applications– Chemical residues

Animals– Pathogens

Human hygiene and health– Pathogens– Virus

Proper sanitation and sanitary conditions

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Drug and chemical residues

Drug residues

Chemical residues

Records of proper labeling, use, handling

Monitor chemical disposition, chemical use in adjacent properties

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Harvesting and handling

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303132333435363738394041

Aug-00

Sep-00

Oct-00

Nov-00

Dec-00

Jan-01

Feb-01

Mar-

01Apr-0

1M

ay-01

Jun-01

Jul-0

1Aug-0

1Sep

-01Oct-

01SHANK FILLET YIELD AS AFFECTED BY SEASON

Bosworth and Wolters, Unpublished

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303132333435363738394041

Aug-00

Sep-00

Oct-00

Nov-00

Dec-00

Jan-01

Feb-01

Mar-

01Apr-0

1M

ay-01

Jun-01

Jul-0

1Aug-0

1Sep

-01Oct-

01SHANK FILLET YIELD

FEMALES MALES

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8

8.5

9

9.5

10

10.5

Aug-00

Sep-00

Oct-00

Nov-00

Dec-00

Jan-01

Feb-01

Mar-

01Apr-0

1M

ay-01

Jun-01

Jul-0

1Aug-0

1Sep

-01Oct-

01NUGGET YIELD

FEMALES MALES

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Catfish Rigor and QualityCatfish is subtropicalStress factors: handling/harvest hold, rapid chilling live fish, transportation, oxygen starvationRested or anesthetized have longer onset than stressed or chilled/stressedRigor onset could be as short as less than one hour to more than 12 hours

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Fish culture/Capture Applications

– A) shocking catfish shocked and held in tubs 2 days:

-Lactate = 49-79 mg% (no deaths)

– B) hoop netting and transported 25 min, weighed, measured, held 2 days:

-Normal appearing fish had Lactate = 39 -112; -Fish with noequilibrium had Lactate= 66 -138%; -Moribund had lactate = 157 -285mg%

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0

20

40

60

80

100

0 2 4 8 11 16 18

Time (hours)

Rig

or In

dex

(%)

ST (Stressed f ish)

NS (Non stressed f ish)

AN (Anesthetized f ish)

CH (Chilled f ish)

Effect of treatment on onset of rigor of catfishNunez and Silva, 2001

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0

1

2

3

4

5

6

7

1 4 7 10 13

Storage time (day)

pH

0

1

2

3

4

5

6

7

ST (pH)

NS (pH)

AN (pH)

CH (pH)

ST (PPC)

NS (PPC)

AN (PPC)

CH (PPC)

pH & PPC of catfish fillets affected by handling

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Post morten changes in fish tissue

Slime secretion in skin: (stops w/ onset of rigor)Rigor mortis: 10-30% shrinkage, soft, spoil, gapping, proteolysisAutolysis and enzymatic decompositionMicrobiological spoilage

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Catfish rigor and qualityRapid onset leads to reddening and tissue softening: Red-Soft-Exhudative (RSE)

Diseases/holding in the sock lead to stress and rapid onset of rigor

Rapid rigor onset may lead to shorter shelf-life

Red fillets have lower pH and about one log cycle lower PPC/TCC than “white” fillets (Lu et al., 2003)

Red fillets may have 2-3 days longer microbiological shelf-life.

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RSE fillets

Red, Soft and Exhudative, RSERed fillets may be the result of stress, on rigor cut fillets, fish that did not bleed completely

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Fish Muscle SofteningCauses:– Spawning, starvation, disease, injury, death

Upon death:– Proteolytic enzymes released– Muscle protein breakdown

Retarded by:– Reduce handling/manipulation– Store @~0C– Do not stack or crush

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Processing

TemperatureTimeInterventionsIcingMarinating

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Icing effect on SL

01

234

567

89

0 2 4 6 8 10 12 14

Storage time (days)

Scor

es

WI

WO

PPC on nuggets

2

3

4

5

6

7

Day1 Day5 Day8

Time(day)

Log

CFU

/g

Control

Treatment

Silva et al., Unpublished

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00.5

11.5

22.5

33.5

44.5

55.5

66.5

77.5

88.5

9

Day0 Day4 Day8 Day12 Day15

Time(day)

Log

CFU/

g CW(HL)TWC(HL)TC(HL)TW(HL)

Silva et al., Unpublished

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Summary

UNIFORMITY OF QUALITY AND STANDARDSOff-flavor management and interventionYield (edible) improvement Rigor onset and its implicationsYiled and quality increases through processing

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Juan L. SilvaDepartment of Food Science, Nutrition and Health PromotionBox 9805Mississippi State, MS 39762Tel: (662) 325-3200Fax: (662) 325-8728

jsilva@foodscience.msstate.edu

MALAHO