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Use of the sensory techniques in Use of the sensory techniques in quality control of foodquality control of food

WORKSHOPWORKSHOP

Emilia Martinsdottir IFL, Iceland

A. Hegyi, T. Kuti, Campden & Chorleywood Hungary

Structure of the workshop

1. Lectures2. Problems related the topics (industry, country)

„What kind of problems do I have to face in the quality control / checking of the final products?

3. Discussion part / Conclusion part

Lectures

Methods

• The existing quality methods• Development of the sensory benchmarking• Sensory evaluation of fish freshness

Quality Control methods

Criteria for sensory quality monitoring system

Requirements of any system that is going to be applied to a production environment:

• Rapid• Uniform• Simple• Reliable • Valid

Quality control / Assurance

Most frequently used methods:

1. Go – no go (positive release)2. Grading, quality rating3. Multiple comparison4. Difference to control –

specific attribute5. Consensus descriptive

(quality index)

Points to consider:

• Culture / Attitude• Resource / Involvement• Test area• Reference samples• Assessor training• Actions / feedback

Attribute or descriptive tests Chambers 1990In/out of specifications Sidel et al. 1983Difference from control measurements Aust 1985

The main steps

• Define a realistic target product – consumer or in house focussed

• Establish a viable acceptance range –commercial risk, consumer loyalty

• Select and train assessors – commitment to quality

• Standardise and document procedures

Defining standard product

• Should present the customer’s requirements.• Key sensory characteristics• Quality range – limits of consumer tolerance• Training aids• Reference samples

Training assessors

• Determine sensory acuity• Calibrate product knowledge – quality range and

tolerances• Validate assessment ability• Training aids• Reference sample

Procedure

• Assessment area

• Number of assessors

• Frequency of assessment

• Sampling and sample size

• Results and actions

1. Go or not go

”In/out” method

• Simple yes/no answer is sufficient sometimes for QC• Identification of reference samples is limited• The resources to train and maintain the more complex

methods are unavailable

In/out specifications

1. Selection of the critical variable attributes2. Selection of ”in/out” limits3. Identification of ”out-of spec” references4. Identification of action standard

In/out specification

Presence ofIn/out

”off color”

limits

Out

”black speck”

Out

”off flavor” Out

……….

2. Grading, classification quality rating

Classification: the items evaluated are sorted into groups which differ in a nominal manner.

Grading: time honoured methods used in commerce which depends on expert graders who learn their craft from other graders, eg. USDA choice.(Meilgaard, Civille, Carr; 1999)

FAO / USDA guidelines; Campden specifications; Codex Alimentarius; National product standards

Grading and scoring the practical approach

Match Acceptable Improvement Needed Reject0 1 2 3 4 5 6 7 8 9

12345

UnacceptablePoorFairGoodOptimum

4321

ExceedTargetSubstandardReject

Classic grading system

• Quick frozen cauliflower, texture

Tender, firm, florets and stalk, yielding to the bite A

Florets may be slightly soft. Stalks may be slightly tough BFlorets may be very soft.

Stalks may be rather tough and difficult to chew CFails to meet the requirements of campden grade C.substandard

The structure of the Hungarian standards• Minimum requirements

• Sensory attributes• Appearance (colour,

shape,..is examined separately.)

• Odour• Taste• Texture

No tolerance

Defining the ideal product (5 scores)•Defects resulting lower scores•General terms are used to describe the ideal properties of main product groups and faults for each scores.eg.bread, rolls,..•Weighting factors for sensory attributesEvaluation

The sum of the scores (the score of the main property is multiplied by the weighting factor) defines the suitability quality of the products, and grade of the products.

MSZ 9441-82 Ice creams sensory assessments

Improvement of the standards

5 4 Ice top on the surface

3Pale colourSome spots, which shows disolvetion

2Ice top on the surfaceIce cream diverges from the packDarker colourSome defects from the melting – melting spots

Weaknesses

1. Not objective-too general descriptions2. Specific properties of specific products are not

described3. Poor indication of specific causes of failures

deviations 4. No fine tuning5. New products with new properties have to be tested

against too the general requirements.eg. poultry

Weaknesses of the Hungarian standard

Test methods• Objectivity• Limited use of definitions• Low sensitivity of indification

of changes properties (time, technology, composition, etc.)

Resources• Number of the assessors• Lack of visual aids• Slow process of changing

3. Multiple comparison

Multiple ComparisonMultiple ComparisonScope:Scope: compare a number of samples to a compare a number of samples to a rreferenceeference, ,

rratingating the level of difference the level of difference -- overall / attribute overall / attribute differencedifference --

Ref. 863 274 519

Principle:Principle:•• identified reference sampleidentified reference sample•• several coded samples in balanced random order several coded samples in balanced random order

(including internal controls) to be compared with (including internal controls) to be compared with referencereference

•• statistical analysisstatistical analysis

Multiple ComparisonMultiple Comparison

Procedure:Procedure:compare each sample to reference in given compare each sample to reference in given

orderorderrating of the size of differencerating of the size of differenceindicate nature of differenceindicate nature of differencepause, cleanser between samplespause, cleanser between samplesno reno re--testingtestingtt--test to test for difference from controltest to test for difference from control

MC EXAMPLE

• Results indicate that all samples are different from the control.

• There is a larger difference with increasing salt.

• The sample means for the two 2g samples are 6.2 and 5.2. While not significant, a difference of 1 on the scale is large.

• Need to look at assessor consistency.

4. Difference to control –specific attribute

Uniformity of colour

defining target defining target

5. Consensus descriptive

Sensory benchmarking

The number of the assessorsminimum 3 trained assessors, + panel leader-sensory acuity-calibrate product knowledge-validate assessment ability-visual aids

The type of the scaleNine unit numeric intervallum scale is the most suitable, but in

some cases due to the simplicity of the products 5 points scale can be used.

0 1 2 3 4 5 6 7 8 9

EvaluationTolerance 1. sample 2. sample 3. sample

Uniformity of shape

5-7 7 5 4 X

Uniformity of colour

5-7 4 X 7 6

Brigthness 4-7 4 8 X 7 X

….

Non-compliance 4 2 5

Non-compliance(%)

27% 13% 42%

Improvement of the sensory benchmarking

The driving factors for the development and implementation of the sensory benchmarking analysis help the preparation of the Hungarian food industry for the EU accession and to improve marketability and competitiveness of Hungarian products on the international market.

We examined the reliability of the new quality assessment method with following tools:

• Comparison of methods• Assessor’s performance

We studied the effects of:

• Sample preparation• Number of assessors

Comparison of methodsComparison of methods:

Traditional method: according to the national standardNew quality assessment: more detailed category scale with 10 pointsNew quality assessment with visual aids: more detailed category scale with 10 points and illustration

Experimental desing:• two-way (3 samples, 5 assessors) cross classification with 3

repetitionsEvaluation:• ANOVA and Gauge R&R analysis for determination of repeatability

and reproducibility

Traditional methods

Hungarian standards

New quality assessment

Appearance-discoloration9 pontA jellegzetes színtől igen erősen eltér. Sötét, elbarnult igen nagymértékben foltos, romlás következtében elszíneződött.

2004.05. 27.

8 PontA jellegzetestől eltérő, foltos, elbarnult, sötétebb.

2004. 08. 13.

7. PontA jellegzetes színtől kissé sötétebb vagy kisséfoltos, kismértékben elszíneződött (nem egész felületen), de nem romlásból eredően.

2005. 11. 24.

Appearance-discoloration5-6 pontA hús marhahúsra jellemzően világos vagy sötétebb piros színű, a húst átszövő faggyú fehér vagy gyengén sárgás. A szín egyenletes, foltosságtól mentes.

2005.01. 19.

4 pontA jellegzetesnél halványabb vagy világosabb, a benne lévő faggyúfehér vagy sárgás.

2005. 04. 11.

New quality assessment with visual aids

0 1 2 3 4 5 6 7 8 9

Whey

Improvement needed

Acceptable MatchRejected

0 1 2 3 4 5 6 7 8 9

Whey

Rejected Improvement needed

Acceptable Match

Comparison of methods

Repeatability & Reproducibility Summary Plot

DD-2 SJ-8 HA-4 FA-3 JG-5

Operators

-6

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Repeatability & Reproducibility Summary Plot

SJ-8 HA-4 JG-5 FA-3 DD-2

Operators

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-4

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Repeatability & Reproducibility Summary P

JG-5 SJ-8 DD-2 FA-3 HA-4

Operators

-6

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Traditional method

New quality assessment

New quality assessment with

visual aids

The plot shows the deviation of the average measured (assigned) values by a panellist from the grand average (lines in the middle of boxes), the difference visually shows the additive error of the panellist. The points within a box are the deviations for the 3 samples from the average given by the panellists. The vertical lines represent the repeated measurements within a sample.

Sample preparation

The appropriate sample presentation can reduce the uncertainty of the results by 50% in the context of odour and by 75% in the context of flavour.

71,4889,88

45,73

86,98

20,8

95,79

020406080

100

(%)

homogenity ofcolour

odour overall flavour

The ratio of variance of the measurement on the example of coffee

Presented on the same temperature Presented on different temperature

Number of assessors

There is no considerable difference between the result of the 2 groups of assessors.

0

20

40

60

80

100

(%)

Colour Uniformity Defects of coat Overall taste Texture Hardness ofthe coat

The comparison of variance of measurement on the example of Cordon Bleu

3 trained assessor 7 trained assessor

Conclusion

With use of visual aids and more detailed, precise category scaling

provides more reliable, more precise, more relevant information than national Hungarian standardsincreases clarity of results it is easy to detect the deviation of the judgements with these statistical tools and according to these evaluation appropriate training can be provided for the assessors

Workshopsthe problematic areas

• there is no standards- mainly international, or the numbers of these standards are limited.

• some methods are just wide-spread, but is not capable for recognition of deviation in the quality.

• lack of proper understanding of advantage of sensory tests• lack of the resources (assessors, facilities,…etc)• ……………………………………

•

Case study

• The company is producing yoghurts with fruity components. The quality is controlled by 1-3 screened people, who are carrying out the sensory tests in the general laboratory. At least in every half an hour they get 2 new samples.

• The company has received more and more consumers' complaints related to the off flavours of the products.

• As a result of this issue the company wants to expand the sensory activity to more accuracy of the quality control.

Case study

TASKS:• Discussing the existing method regarding the

complaints! Can it be improved?• Discussing the possiblity of setting/adding a

dedicated sensory panel? Which type of methods should they use?

• How and when do you use consumer tests in this case?

Discussion

IIcelandiccelandic Fisheries Fisheries LaboratoriesLaboratories

SkSkúúlagatalagata 4, IS4, IS--101 101 ReykjavReykjavíík, Iceland k, Iceland

Tel: +354 5308600, Tel: +354 5308600, email: email: emilia@rf.isemilia@rf.is

Campden ChorleywoodHungary

1107 Budapest Szállás str.21. Tel: 36 - 1 433 14 70Fax: 36 - 1 433 14 80www.campden.co.uk

www.campden.hue-mail: campden@campdenkht.com

Thank you for attention!