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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: [email protected]@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