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Workshop: Use of sensory techniques in quality control of food

Sensory Evaluation of Fish FreshnessSensory Evaluation of Fish Freshness

EmilEmilííaa MartinsdMartinsdóóttirttir

Icelandic Fisheries LaboratoriesIcelandic Fisheries LaboratoriesSkSkúúlagatalagata 4, IS4, IS--101 Reykjav101 Reykjavíík, Iceland k, Iceland Tel: +354 5308600, email: Tel: +354 5308600, email: emilia@rf.isemilia@rf.is

The content of the lectureMethods for sensory evaluation of fish

importance of freshnessuse of sensory evaluation

The QIM-methodHow to develop a QIM-schemeReference manual

Use in industryConclusions

Why is sensory evaluation of fish important!

Sensory evaluation of fish freshness gives valuable information on qualityFish is very perishable, can be kept on ice 8-20 days depending on species

Spoilage is species related - Many different species

Freshness and changes in sensory attributes are critical parameters during food production

Time and temperature is of main importance

Fish is transported all overFish is sold via e-commerce

Sensory evaluation in the fishery chain

FIsh auction

Consumers

Retailers

Fresh fillets

Consumers

Retailers

Frozen fillets

Fish processing plant

Landing

Fishing vessel

Sensory evaluation of whole fish

Sensory evaluation of raw and cooked filletsSensory evaluation of cooked fillets

Methods for sensory evaluation of fish freshness in the industry

EU scheme Grading scheme for whole fish EU scheme is commonly accepted in the EU countries E, A, B / unfit

QIM (Quality Index Method)Bremner,1985Demerit points 0-3 added to give an index

Torry scheme for both whole and cooked fishShewan, 1953scoring system (10-1)

Not Extra A B Admitted

Skin Bright, iridescent pigment Pigmentation bright but Pigmentation in the Dull pigmentation(save for redfish) or not lustrous process of becomingopalescent; no discoloured and dulldiscolouration

Skin mucus Aqueous, transparent Slightly cloudy Milky Yellowish, grey,opaque mucus

Eyes Convex (bulging), black, Convex and slightly Flat, opalescent cornea, Concave in the centre,bright pupil, transparent sunken; black, dull pupil, opaque pupil grey pupil, milkycornea slighly opalescent cornea cornea

Gills Bright colour, no mucus Less coloured, Brown / green becoming Yellowish, milky mucustransparent mucus discoloured, thick,

opaque mucusPeritoneum on Smooth, bright, difficult Slighly dull, can be Speckled, comes away Does not stickgutted fish to detach from flesh detached from flesh easily from fleshSmell of gills andabdominal cavity>whitefish other Seaweedy No smell of seaweed, Fermented, slightly sour Sour than plaice: neutral smell>plaice: Fresh oily, peppery Oily, seaweedy or Oily, fermented, stale, Sour

earthy smell slightly sweetish slightly rancidFlesh Firm and elastic, smooth Less elastic Slightly soft (flaccid), Soft (flaccid), scales

surface less elastic, waxy easily detached from(velvery) and dull skin, surface rathersurface wrinkled

CriteriaFreshness category

EU-scheme

White fish: Haddock, codsaithe, pollock, redfish, whiting, ling, hake, Ray´s bream, anglerfishpouting and poor cod, bogue, picarel, conger, gurnard, mullet, plaice,mergrim, sole, dab,lemon,sole, flounder,scabbard fish

Disadvantages of grading schemes like the EU-scheme

Grouping several, different sensory terms into one quality gradeSensory characteristics disagree with other subdescriptions of the quality grade

confusion of the grader, increased timedecreases the objectivity of the evaluation

Not species related

QIM-schemefor Sea bass

Quality parameter Description Score

Skin Colour/ Bright, iridescent pigmentation 0appearanceRather dull, becoming discoloured (head) 1

Green, yellowish, mainly near the abdomen 2Odour Fresh seaweedy, neutral 0

Cucumber, metal, hey 1Sour, dish cloth 2Rotten 3

Texture In rigor 0Finger mark disappears rapidly 1Finger leaves mark over 3 seconds 2

Eyes Pupils Clear and black, metal shiny 0Grey 1Mat, grey 2

Form Convex 0Flat 1Sunken 2

Colour Blood red/orange 0Pale red, pink/light brown 1Grey-brown, brown, grey 2

Mucus Transparent 0Milky, clotted 1Brown, clotted 2

Odour Fresh, seaweed, neutral 0Metal, grass 1Sour, mouldy,dish cloth 2Rotten 3

Flesh, filleColour Translucent, bluish 0Waxy, milky 1Opaque, yellow, brown spots 2

Solution Whole 0Beginning to dissolve 1Viscera dissolved 2

Quality Index 0-22

Gills

Viscera

Advantages of the Quality Index Method (QIM)

The relevant attributes are all evaluated and given scores according to their imporanceThe inspector has to evaluate each attributeMinor differences in judgements in one attribute do not influence the total score Useful to teach inexperienced people Useful to train and harmonise inspectorsLinear relationship between Quality Index and storage time in ice

QIM scheme is developed for a new each fish species

Development of QIM schemeselection of experienced QIM assessorspurchasing of super fresh fishcontrolled storage experimentday-to-day description of the sensory attributesdraft schemevalidation and linear regressionend-of-shelf lifepractical implementation

y = 0,6921x + 1,5676R2 = 0,9533

0

6

12

18

24

0 5 10 15 20 25

Days in ice

QI score

Practical session

With max 5 experienced QIM assessorsexperienced in sensory assessmentsgood vocabularyexperienced panel leader

day-to-day descriptionfive fishes a time (do not re-use them)discussion during observationwrite down all comments from everyonecontinue one day after fish is definitely spoiled

Draft scheme

Select the attributes which changed during the storage timegroup the descriptions with major changesadd scores 0 very fresh, to max 3 at end of changesmake a draft QIM scheme

Changes in sensory attributes during storage of ocean perch

Gills

Colour : Blood red Score = 0

Mucus: Clear

Score = 0

Eyes

Cornea: Clear

Score = 0

Form: concave

Score = 0

Eyes

Cornea: milky

Score = 2

Form: sunken

Score = 2

Mucus:

Discoloured, clotty Score = 2

Right score for each description?Texture

0,0

0,51,0

1,5

2,0

0 5 10 15 20 25

Days in ice

Score

Gills odor

0,00,51,01,52,02,53,0

0 5 10 15 20 25Days in ice

Score

Individually assessment of all attributes over the storage period

How do they changedo they increase are all the scores 0, 1,2 3, used

Right score for each description?

Multivariate analyses of all data.

Make a PCA analyses of all results and decide if an attribute contributes enough to the total QIM score and to the storage time

0.6

0.4

0.2

0

0.2

0.4

0.6

0.25 0.26 0.27 0.28 0.29 0.30 0.31 X-expl: 82%,4%

•Days in ice

•Skin colour

•Skin mucus

•Skin odour

•Texture

•Eyes pupils•Eyes form

•Gills colour

•Gills mucus•Gills odour

•Abdomen blood

Abdomen odour•

PC1

PC2 X-loadings

Validationnew storage experimentuse the draft QIM scheme individuallydiscuss the scoring after every sessionadjust the descriptions and scoresdetermine “end-of-shelf life”

simultaneously use sensory evaluation of cooked samples by expert panel

Torry schemeQuantitative Descriptive Analyses (QDA)

Torry scheme for the evaluation of cooked cod

Odour Flavour ScoreSweet, cooked milk Watery, metallic 10

Shellfish, cooked meat Sweet, meaty 9

Faint, neutral Sweet but more faint 8

Wood, vanilla Neutral 7

Cooked potatoes Insipid 6

Boiled clothes A little sour, faintTMA

5

Sour milk, TMA Bitter,sour, TMA, 4

End of shelf life

Average score = 5.5

Changes in Quality Index and eating quality (Torry-score) during storage of iced haddock

Linear relationship -QI can be used to predict Torry-scoreQIM used on whole raw fish could replace sensory evaluation of cooked samples.

QIM is more rapid and is performed earlier in the production chain.

0

5

10

15

20

0 5 10 15

Storage time (days)

Qua

lity

inde

x-Q

I

2345678910

Torr

y sc

ore

QI-MayQI-DecTorry-MayTorry-Dec

QDA evaluation of end-of-shelf life for salmon

increase of negative attributesdetection of spoilage flavourssignificant difference at 20-22 days (for positive as well as negative flavours)

0

20

40

60

80

100

0 5 10 15 20 25Days in ice

Score

Sour Musty, earth Rancid

Negative QDA flavour changes

Finalising the QIM scheme

Describe the assessment of the fishMake professional photographs

on relevant attributesuse one batch, make photographs every dayno ‘commercial’ pictures

calculate reliability of the calibration curvehow many fishes per batchprediction of storage time st.dev.

Convex form of eye

Firm texture

Linear relationship between QI and storage time in ice

Scientific development of QIM for various species Quality Index increases linearly with the storage time.

For use in the industry - Evaluate QIPredicted storage time in ice is defined as the number of days that the fish has been stored in ice.Shelf life is defined as the number of days that whole, fresh (gutted) fish can be stored in ice until it becomes unfit for human consumption -Storage studiesAn estimate can be calculated for the remaining shelf life (= shelf life-predicted storage time).

QIM in Quality and Production Management

0

5

10

15

20

25

30

0 5 10 15 20

Predicted storage time in ice

Qua

lity

Inde

x

Remaining shelf-life

Estimated shelf life

Remaining shelf- life

Plaice

Salmon

QIM-manual in 11 languages

English, Dutch, Danish, French, German, Greek, Icelandic, Italian, Norwegian, Portuguese and Spanish!Sensory evaluation of fish

The Quality Index Method (QIM)for 12 fish species

Guidelines for sensory evaluation of fishFacilities for sensory evaluationSample preparation of cooked samples and procedure for the sensory evaluationSelection and training of panellists

Shelf life of whole fishUsing QIM in process- and quality management

ConclusionsQIM is developed and recommended by fish

research institutes Rapid, objective sensory method QIM is used in research Use in fish auctions has increasedInterest of the fish sector has increased

For further progress and development of QIMImplementation

in fish auctions and fish processing plantstraining of assessorsimplementation of QIM (at the first point of sale) stimulated if the EU Council regulation (2406/1996) would incorporate QIM

Develop schemes for more fish species!!

ConclusionsQIM-schemes could be developed for other food

quality controlsame language for buyers and sellersphotographs

QIM-homepagehttp://www.qim-eurofish.com/

Attribute Description Score

Appearance Skin Bright, iridescent pigmentation 0Rather dull, becoming discoloured 1Dull 2

Stiffness In rigor 0Firm, elastic 1Soft, 2Very soft 3

Cornea Clear 0Opalescent 1Milky 2

Form Convex 0Flat, slightly sunken 1Sunken, concave 2

Pupil Black 0Opaque 1Grey 2

Colour Bright 0Less coloured, some discoloured 1Discoloured, brown spots 2Brown, discoloured 3

Smell Fresh. seaweedy, metallic 0Neutral, grassy, musty 1Yeast, bread, beer, sour milk 2Sulphuric, very sour 3

Mucus Clear 0Milky 1Milky, dark, opaque 2

Flesh, fillets Colour Translucent, bluish 0Waxy, milky 1Opaque, yellow, brown spots 2

Colour Red 0Dark red 1Brown 2

Quality index 0-23

Eyes

Gills

Blood

QIM-EUROFISHQIMCHAIN-project Information on QIM methodAll QIM-schemes presented New articles on QIM

Thank you for your attention!

Acknowledgements :

Rian Schelvis-Smit and Joop Luten RIVO

Grethe Hyldig DIFRES

Kolbrún Sveinsdóttir IFL