factors affecting fish quality focus on farmed salmon

Factors Affecting Fish Quality:Focus on Farmed Salmon

Dave RobbEWOS Innovation

What is Fish Quality?

• Quality is many things to different people– Consumers– Processors– Retailers / Food Service

• Quality includes– Appearance– Texture– Eating quality– Chemical constituents– Food safety– Ethical concerns

Is Fish Quality Important?

• When demand exceeds supply, quality does not pay extra – certification schemes may

• When demand is limiting, then quality is important

• Quality is also important to gain consumer confidence and repeat sales

• If quality varies too much, consumers do not understand this and will purchase something else

• Value added processing can cover a range of quality issues – upgrading poor quality for some products

Factors Affecting Fish Quality

Which aspects?• External condition

– Shape– Fins– Scales and skin

• Internal condition– Fat content– Colour and Pigment– Gaping– Texture– Bloodspotting– Eating quality– Shelf-life

• What can affect these?– Genetics– Freshwater husbandry– Seawater husbandry– Nutrition– Growth rates– Harvest– Storage Changes

• There is a lot of variation in what happens in all of these areas (nutrition is probably the least)

What is Flesh Quality?

Consumer Assessed• Appearance• Eating Quality

Technological• Texture• Processability

– A lot of value added products made with fish

Appearance

External• Shape• Cuts and bruises• Net marks• Fin and tail erosion• Eye damage• Scale loss

Appearance

Internal• Fat – width • Colour• Bloodspotting• Haemorrhages / Bruises• Vaccine scars• Gaping

Texture

• Very important indicator of freshness• Also essential for all value added products

• Gaping – holes in the product• Soft flesh – poor yield and rough cuts• Fatty flesh – poor yield

Bloodspotting

Bloodspotting Challenges

Vaccine Scars

• Melanin deposits in the muscle and viscera• Caused by reaction to adjuvants in vaccines

Technical Quality

• Gaping• Soft flesh• Gutting and filleting• Storage stability• Freezing• Salting• Smoking

Where is Flesh Quality Affected?

Genetics

• Growth rates• Fat• Colour• Muscle Fibre Number

• Tool for the future• Need to develop with value chain• Target strains for diets

Stock on Muscle Fibre Number and Area

Ref: Johnston et al 2000

Why is Fibre Number Important?

Ref: Johnston et al 2000

Egg Incubation Temp

• Range of temps from 2°C to over 10°C been used

• Found that over 8°C and sudden temp fluctuations can cause range of deformities

• Affects muscle fibre number later in life• Muscle fibre can be affected throughout life, but

most strongly affected at this stage

• Affects gene expression• Higher temp, rates are faster, perhaps not giving

enough time for impact of expression• Could explain some of the deformities observed

Effect of Incubation Temperature

From 8 to 10 oC

From 8 to 12 oC

05

101520253035404550

Temperature increased at:

110 do 220 do 330 do hatching

Muscle Fibre Number8 C or 5 to 7°C

Visceral DeformitiesIncubation Temps

• Variation between sites – on top of stocks• Probably due to environmental differences• Well shown by company monitoring program

Colour by Site

20.0

22.0

24.0

26.0

28.0

30.0

0 1000 2000 3000 4000 5000 6000Live Weight (g)

Mean DSMSalmoFan

Farm Site

Fat By Site

0

5

10

15

20

25

30

0 1000 2000 3000 4000 5000 6000Live Weight (g)

FatContent

(%)

ATS: Fat content by Live Weight

Fat in Salmon Fillet

Gaping / Soft Texture

• Fish are soft generally compare to meat• Low amount of collagen, etc• More likely to gape• Working with customers to develop diets to

reduce gaping

• Fixer diet to reduce severe gaping

EWOS Trial Results

• Effect of increased dietary oil on gaping• Low Oil showed more gaping than High Oil• But lots of variation within treatments

0 1 2 3 40

10

20

30

40

0 1 2 3 4Gaping Score

Low Oil High Oil

0

10

20

30

40

n

Diet on Gaping

Gaping ScoreTGC > 0

Gaping ScoreTGC > 1.5

Dietary Treatment Dietary Treatment

Starvation

Fat Content

Body composition remains unaffected

0 20 40 60 80 1000

6

12

18

MuscleLipid(%)

Days Starved Einen et al 1998a

Harvest

Harvest Requirements

• Need a system which keeps the fish calm throughout –stress and activity at any stage will downgrade– Trained staff– Good systems – keep fish activity low and kill fish

rapidly, without stress (good welfare)– Monitoring and feedback

• Activity results in muscle lactic acid build up– Decreased time to rigor onset– Firmer rigor – greater rigor force on muscle– Change in muscle protein conformation– Loss of colour and translucency– Loss of texture and muscle strength

Withdrawlof Feed

Withdrawlof Medication

Well BoatAmbient

Temperature(4)

Crowding(1)

Crowdingand Grading

(1)

Well Boatwith

Chilling(4)

Crowding inAQUI-S orClove Oil

(1)

Legend

Point where fish are stunned or die if procedure carriedout correctly

Numbered critical control point for fish stress and activity.Note: more control points does not necessarily mean a worse system.

(1)

HarvestRoadmap

Point where fish die if procedure not carried out correctly

Shore basedKilling Site

(4)

Transport toProcessing

Plant

Live Chilling (5) Bleeding (6)

Carbon Dioxide (5) Bleeding (6)

Percussive Stunning (5) Bleeding (6)Transport toProcessing

Plant

Gutting

Gutting


MovableHarvest Cage

(4)

Held overnight(6)

Crowded(7)

Removed from Cage

(8)

Towedto Shore

(5)

Shore basedKilling Site

(9)Carbon Dioxide (10) Bleeding (11)


Plant


PlantGutting

Gutting

Held in WellBoat Overnight

(6)

Removed fromWell Boat

(7)

Into Slaughtery

(8)


Percussive Stunning (9) Bleeding (10)

Electrical Stunning (9) Bleeding (10)


Gutting

Gutting

Gutting

Gutting

Transportto Slaughtery

(5)


(6)

Into Slaughtery

(7)





Gutting

Gutting

Gutting

Gutting

Held in WellBoat Overnight

(6)


(7)

Into Slaughtery

(8)





Gutting

Gutting

Gutting

Gutting


(6)

Transportto Slaughtery

(5)

Into Slaughtery

(7)





Gutting

Gutting

Gutting

Gutting

Holding Cageat Slaughtery

(7)

Crowded(8)

Removed from Cage

(9)

Discharge(6)

Into Slaughtery

(10)





Gutting

Gutting

Gutting

Gutting

Harvest Vessel

(4)

Bleeding (6)AQUI-S anaesthesia (5)



Plant


PlantGutting

Gutting

Brailling (2) Harvest Vessel

(3)


Plant

Bleeding (5)Carbon Dioxide (4)

Bleeding (4)


PlantGutting

Gutting

Live Fishin the Main

Growing Cage

Removal from cage

(3)

Fish Readyfor Harvest

FishCrowded

(2)BraillingVacuum PumpAir liftVenturi PumpSiphoning

Vacuum PumpDirect to Shore

Swim from onecage to next

BraillingVacuum PumpAir liftVenturi Pump

Change in muscle strength

0

1

2

3

GapingScore

0

20

40

60

80

FailureStress(kPa)

Rested

Active

Less likelyto break

Jerrett et al 1996 and Robb et al 2000

Harvest Impacts

• Big driver on rigor onset– Possible to be 60h pre-rigor– Commercially can send fish into full rigor in

45min– Best times seen between 30 and 40h– Full system control required

• This has a big impact on processing times• Must not process in rigor or get gaping and poor

yields

Quality Conclusions

Quality is Very Complex

• Lots of factors throughout the value chain affect quality

• Lots of interactions• Training and awareness at any one point is

essential

The Value Chain is the Strongest Tool

factors affecting fish quality focus on farmed salmon

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