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
OI 2007 3
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
OI 2007 4
Catfish Quality and Safety
Spoilage– Off-color and off-
flavor– Enzymatic– Microbiological– Oxidative
Hazards– Chemical residues– Drugs– Microbiological– Metals
OI 2007 5
Species, site selection & soil
SpeciesSite selection – floods, – soil, – animals
Soil – heavy metals,– chemicals
OI 2007 6
Production practices
Stocking density
Environmental management
OI 2007 7
Water source & water quality
Water source– pathogens, – chemical residues– Off-flavors
Water quality management and control– chemical residues– Off-flavors
OI 2007 8
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.
OI 2007 9
Feed quality and feeding regime
Feed quality – Protein– Antioxidants– Pigments– Pathogens/Toxins– Drugs
Feeding regime/practices– Season– Satiation
OI 2007 10
Yellow pigmentation
• Usually the result of yellowpigments (asthaxanthins) in the feed or lagoon (yellow corn feed, algae), usually along fatty tissue
OI 2007 11
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
OI 2007 12
Drug and chemical residues
Drug residues
Chemical residues
Records of proper labeling, use, handling
Monitor chemical disposition, chemical use in adjacent properties
OI 2007 13
Harvesting and handling
OI 2007 14
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Bosworth and Wolters, Unpublished
OI 2007 15
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
OI 2007 16
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
OI 2007 17
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
OI 2007 18
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%
OI 2007 19
OI 2007 20
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
OI 2007 21
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
OI 2007 22
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
OI 2007 23
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.
OI 2007 24
RSE fillets
Red, Soft and Exhudative, RSERed fillets may be the result of stress, on rigor cut fillets, fish that did not bleed completely
OI 2007 25
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
OI 2007 26
Processing
TemperatureTimeInterventionsIcingMarinating
OI 2007 27
OI 2007 28
OI 2007 29
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
OI 2007 31
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
OI 2007 32
Summary
UNIFORMITY OF QUALITY AND STANDARDSOff-flavor management and interventionYield (edible) improvement Rigor onset and its implicationsYiled and quality increases through processing
OI 2007 33
Juan L. SilvaDepartment of Food Science, Nutrition and Health PromotionBox 9805Mississippi State, MS 39762Tel: (662) 325-3200Fax: (662) 325-8728
MALAHO