The Provision of Sensory Training at Foundation Level
The Institute of Food Science and Technology
5 Cambridge Court
210 Shepherds Bush Road
Tel: 44 (0)20 7603 6316
Fax: 44 (0)20 7602 9936
The IFST Trust Fund is a registered Charity No. 264044CONTENTS
Scientific Discipline 5
Senses and sensory properties 5
Sensory Responses 5
THE BASIC SENSES 6
The Sense of Sight (Vision) 6
The Sense of Smell (Olfaction) 6
The Sense of Taste (Gustation) 7
The Sense of Touch (Tactile) 7
The Trigeminal Senses 8
The Sense of Hearing (Audition) 8
Sensory Interactions 9
THE SENSORY PANEL 9
Recruitment and Screening 9
GOOD PRACTICE: CONTROL OF TEST ENVIRONMENT 10
Test Room 10
Assessor Control 11
TESTS AND USES 11
Types of test 11
Discrimination Tests 12
Descriptive Profile Methods 12
Temporal & Dynamic Methods 13
Acceptance and Preference Tests 13
BASIC STATISTICAL CONCEPTS 13
An individual achieving Foundation level should be able to: 13
Populations and Samples 14
Probability and Hypothesis Testing 14
RECOMMENDED TEXTS 16
INTRODUCTION The following document details the syllabus for foundation level training in Sensory Science. The syllabus is divided into six sections, which represent the key fundamental areas of study required for individuals with little or no previous experience. The foundation course may be used as a starting point for those who may wish to pursue a career in sensory science and as a refresher for technicians currently working in sensory science. It can also be used as an overview for staff from product development, marketing, consumer insights or quality control/assurance wishing to become more involved with sensory departments.
Please note: the syllabus is intended to primarily develop appreciation of the areas addressed; not provide in-depth knowledge. The focus is on analytical aspects of sensory evaluation that require screened and trained assessors; not on consumer testing.
The syllabus is NOT designed to be used for training sensory assessors.
In order to cover all areas detailed in the syllabus, a combination of teaching methods should be used e.g. pre-course work, formal lectures, student discussion groups, practical activities and handout materials. Furthermore, to keep the students’ attention and interest, a variety of audio visual aids should be employed. The course takes 1 day or a total of 6 hours to complete.
For courses to be accredited they must demonstrate coverage of learning outcomes in each sub section (i.e. 1.1, 1.2, 1.3. etc.) of the six sections that make up the syllabus, and must cover at least 80% of the overall learning outcomes. Furthermore, specific learning outcomes must be covered as a matter of course. These compulsory learning outcomes are italicized and underlined in the syllabus. See the guidelines for accreditation for further details.
It is key that those delivering training demonstrate competence in the risk assessment of health and safety issues and show an awareness of ethical issues in the sensory assessment of food and non-food products.
SPECIAL NOTICE No part of this syllabus may be reproduced in a retrieval system or transmitted in any form or by any means, electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise without prior permission in writing, from the Institute of Food Science & Technology. If granted, it will be on the understanding that the syllabus or extract thereof is accompanied by acknowledgement to the IFST, a statement that this is an extract (if applicable) from this publication, full reference to the syllabus, with an indication that it is available from the IFST Office.
DEFINITION An individual achieving Foundation level should be able to:
Scientific Discipline Recognise that sensory analysis is a scientific discipline that requires standardisation and appropriate controls at all stages (from preparation of the samples to evoke the response, to measuring, analysing and interpreting the response).
And formally define sensory evaluation as “a scientific discipline used to evoke, measure, analyse, and interpret reactions to the characteristics of food and materials as they are perceived by the senses of sight, smell, taste, touch, and hearing.” Express the need for careful documentation at all stages. Distinguish between the scientific approach and the 'journalistic' approach often seen on TV. Differentiate between objective sensory tests and subjective consumer tests. Indicate that both food and non-food materials can be evaluated by sensory analysis: pasta to perfume, nougat to nappies, and fabric to fertiliser! Senses and sensory properties Identify how all the five senses, sight, smell, taste, touch and hearing are involved in sensory analysis.
Define the characteristics of a product in broad categories: appearance, texture, flavour (which includes taste and odour) and sound.
Identify that a wide range of different attributes may be perceived by the senses within these broad characteristics.
State that interactions between these characteristics may influence sensory analysis.
Sensory Responses Recognise that both physiological and psychological factors affect an individual’s perception and subsequent response to stimuli.
Identify that trained assessors are being used as instruments and as such their responses to sensory stimuli need to be standardised and calibrated.
Explain that the type of assessors may range from those who have undergone a minimum of screening and selection to those considered experts on a particular product.
State that the degree of training will depend on the test being undertaken, and that descriptive profiling methods will require a greater amount of training compared to discrimination methods.
THE BASIC SENSES An individual achieving Foundation level should be able to:
The Sense of Sight (Vision) Describe the basic structure of the eye and that rods and cone cells on the retina convert light energy to neural impulses to the brain via the optic nerve.
Express the incidence of colour blindness (red/green most common occurs in approximately 810 % of males and 0.4% of females) and the need to screen for visual impairment (see Section 3: The Sensory Panel).
Outline how test conditions might be used to disguise some appearance attributes so they do not influence the assessment of other attributes e.g. use of coloured lighting.
The Sense of Smell (Olfaction) State that volatile molecules are sensed by the millions of hair-like cilia that cover the nasal epithelium (located in the roof of the nasal cavity), although the mechanism for distinguishing between different types of odour molecule is still unclear.
Explain that Anosmia is the total or partial loss of the sense of smell and can be permanent or temporary. Also be aware that selective anosmia is insensitivity to a specific group of compounds e.g. phenolic compounds.
State that for a product to have an odour/aroma, volatile molecules must be transported in air to the nose.
State that the volatile molecules can enter the nose orthonasally (by active sniffing/breathing) or retronasally (via the back of the throat during eating).
State that there are a very large number of volatile compounds in food, and a single perception can arise from a mixture of volatile compounds e.g. strawberry aroma.
Review the fact that many words can be used to describe a single compound (e.g. thymol = herb-like, green, rubber-like) and that a single term can describe many compounds (e.g. lemon = -pinene, -limonene, citral, citronellal, linalool etc.
The Sense of Taste (Gustation) Describe gustation as the mechanism by which non-volatile substances dissolved in water, oil or saliva are detected by chemical receptors in the taste buds.
State that taste buds are located on the surface of the tongue and other areas of the mouth or throat.
Explain that stimulation of taste receptors results in 5 different taste responses - salty, sweet, acidic (sour), bitter and umami.
Group non-volatile compounds dependent on the taste response they elicit:
Salty compounds e.g. sodium chloride, potassium chloride
Sweet compounds e.g. sucrose, fructose, glucose, aspartame
Bitter compounds e.g. quinine, caffeine
Umami compounds e.g. monosodium glutamate.
Recognise that all areas of the tongue can be sensitive to taste compounds but that some areas are more sensitive than others.
State that Aguesia, a rare neurological condition, is the total loss of the sense of taste. Hypoguesia is partial loss of one or more of the taste sensations.
The Sense of Touch (Tactile) Explain that tactile receptors on the surface of the lips, tongue, face and hands detect differences in force, particle size, heat and chemical stimulus during hand and mouth touch.
Recall that nerve fibres in the muscles, tendons and joints sense the tension and relaxation of the muscles and allow the perception of attributes such as heaviness and hardness.
State that texture is complex and related to food structure and can be divided into three elements, mechanical, e.g. hardness and chewiness; geometric e.g. graininess and crumbliness; and mouth feel e.g. oiliness and moistness.
List the three stages of texture perception:
Initial phase (first bite)
Masticatory phase (chewing)
Residual phase (after swallowing)
Be aware of factors that may affect tactile perception e.g. poor dentition, dry mouth, skin hydration, etc.
The Trigeminal Senses State that the trigeminal nerve is primarily responsible for transmitting sensations from the face (mouth, teeth and nasal cavity) to the brain, and controls the muscles used for chewing.
Explain that certain chemical substances can stimulate the trigeminal nerves to give hot, burning, tingling or cooling or astringent sensations (e.g. piperine in pepper, capsaicin in chilli pepper, carbon dioxide in fizzy drinks).
The Sense of Hearing (Audition) State that sound is sensed by millions of tiny hair cells in the ear (receptors) which are stimulated by the vibration of air from sound waves.
Recognise that the noise emitted by food during eating contributes to the perceived texture of a food.
Be aware that loss of hearing can occur due to illness, genetics, age, which may affect texture perception.
Sensory Interactions Describe how appearance can influence other attributes e.g. colour - visual flavour (orange colour suggests orange flavour); colour intensity can lead to assumption about flavour intensity; unevenness of colour or blotchy appearance may suggest poor quality or deterioration.
Clarify that odour combines with taste and trigeminal stimulation to give flavour.
Sensitivity State that individuals differ in their sensitivity to the same compounds (see Section 3 – The Sensory Panel).
Recognise that different threshold levels for individuals can be determined through screening – detection, recognition, just noticeable difference and terminal.
List factors that may affect sensitivity to smell and taste e.g. oversaturation, ageusia, anosmia, ill health, personal habits, age etc.
THE SENSORY PANEL An individual achieving Foundation level should be able to:
Recruitment and Screening Define the factors that will influence the recruitment and selection of assessors e.g. management resource, test frequency, test method, company policy.
State the key advantages and disadvantages of using internal and external assessors e.g. resources, time, space.
Identify suitable personality and attitude factors when recruiting assessors e.g. good team player, cosmopolitan taste preferences, positive, committed and flexible, ability to use computerized data collection equipment.
Explain why it is important that the assessors should have at least normal sensory acuity relative to the tests being undertaken.
Review how the state of health affects sensory acuity and the need to be aware of physiological restrictions relevant to the test e.g. allergies, false teeth, migraines etc.
Select and apply different panel screening tests, e.g. those aimed at determining sensory acuity, those aimed at determining impairment, those aimed at evaluating an assessor’s potential to describe and communicate.
Interpret the results of the screening tests and apply these to selection of assessors for different sensory methodologies.
GOOD PRACTICE: CONTROL OF TEST ENVIRONMENT An individual achieving Foundation level should be able to:
Test Room Describe how the physical environment must work so as to minimise bias, enhance assessors’ sensitivity and eliminate variables unconnected with the products being analysed.
Recognise important considerations when designing a test facility e.g.
Locating away from areas of noise and odour and sample preparation areas.
Avoiding claustrophobic design.
Use of odour free easy clean materials.
Pale grey or white colour for surfaces and surroundings.
Necessary equipment for sample preparation.
Lighting onto samples needs be evenly distributed.
The use of Northern Daylight lighting is recommended for standard assessments. Coloured lighting is recommended when visual distractions need to be minimized.
Control of air circulation, humidity and temperature.
Outline important issues concerning the presentation of samples e.g.:
Odour-free and easy to clean equipment (glass, china and stainless steel rather than plastic or wood).
Consistent portion size, representative of the sample to each assessor.
Sample carriers (if used) should not mask sample’s attributes.
Controlled serving temperature.
Standard procedures e.g. controlled/standardised cooking regimes.
Sample coding – commonly 3 digit random codes.
Balanced, random order of presentation.
Maximum number of samples per session dependent on product type.
State the need to keep good records i.e. date codes, test required, storage etc.
Identify key health and safety risks related to ingesting or handling food and non-food products Assessor Control State the need to provide any necessary training/information for the panel to conduct the test e.g. use of score sheets, test methods etc.
Explain the consequences of poor panel scheduling e.g. eating foods at inappropriate times of day or around coffee breaks or lunchtimes.
Recognise that certain physiological factors may influence panel results e.g. adaptation.
Recognise that certain psychological factors may influence panel results e.g. Expectation errors, Stimulus error, Halo effect.
Identify that assessors must be in good health and adopt sensible personal habits before/during sessions e.g. avoiding smoking 1-2 hours before panel, strong coffee for 1-2 hours before panel and the use of strong smelling cosmetics/soap.
TESTS AND USES An individual achieving Foundation level should be able to:
Types of test
Outline the three main categories of sensory test i.e. discrimination; descriptive and preference/acceptance, and their uses. Discrimination Tests Explain that discrimination tests are used to determine if there is a detectable difference between two types of samples being compared in the same session.
Name typical discrimination tests and specify the differences between them e.g. Paired Comparison, Triangle, Duo Trio, Tetrad.
Recommend the minimum number of assessors required for commonly used discrimination tests (paired comparison, triangle test, duo trio) and how this depends on the degree of panel training.
Be aware that many more assessors are required for Similarity Tests than for Difference Tests.
List typical applications and limitations for discrimination tests.
Descriptive Profile Methods Express that descriptive profile methods are used either to describe, or describe and quantify, the attributes of the samples and produce a sensory profile.
Identify that different types of scale may be used to quantify the individual attributes e.g. category, unstructured line, magnitude estimation, labelled magnitude.
Outline the stages in the development of a sensory profile to test a set of samples – i.e. development of vocabulary, rating of attributes, analysis of the data.
Recognise that there are several established techniques (Quantitative Descriptive Analysis, Spectrum Method, consensus profile, qualitative profile, free-choice profile) with the same underlying basic approaches.
Be aware that it is not uncommon for hybrid descriptive profile methods consisting of a combination of elements from two or more of the established methods to be used.
Recognise that the level of training is crucial for descriptive profile tests and describe the consequences of the degree of training on the quality of the sensory data obtained.
State that descriptive profile techniques require a small number of highly trained assessors.
Discuss the typical applications and limitations of descriptive profile tests.
Be aware of rapid descriptive methods e.g. Free Multiple Sorting, Napping (Projective Mapping), Partial Napping, that speed up data capture but that analysis of the data is more complex compared to conventional profiling.
Temporal & Dynamic Methods Recognise that these methods enable perception to be measured over time.
Be aware that established methods are available e.g. Time Intensity (TI), Temporal Dominance of Sensations (TDS), Progressive Profile, whilst others are evolving e.g. Temporal Check-all-that-apply (TCATA), Temporal Order of Sensations (TOS).
Acceptance and Preference Tests Understand the difference between Acceptance and Preference Tests.
State that acceptance tests e.g. 9 point hedonic scale, measure degree of liking.
State that paired comparison and ranking tests can be used to measure order of preference
Recognise that a large number of untrained consumers are required for acceptance and preference tests to best represent the population. Trained assessors should not be used for acceptance or preference tests.
BASIC STATISTICAL CONCEPTS An individual achieving Foundation level should be able to: Populations and Samples State that a population refers to all the objects or individuals that define a group of interest. For example, the population of the UK or all consumers of a particular brand of chocolate.
State that a sample from a population can be defined as selected objects or individuals chosen to represent the population. Note that it is important to select a sample of objects or individuals that represent the population to ensure that decisions made based on the data are as meaningful as possible.
State that the mean, sometimes called an average in layman’s language, is a measure of the middle (centre) of a set of data, and that it is sometimes called an ‘arithmetic mean’. Understand that it is obtained by adding up the values of all the observations and dividing by the total number of observations. For example, the mean of 8, 4, 6, 9 and 2 is:
(8 + 4 + 6 + 9 + 2)/5 = 29/5 = 5.8
State that the standard deviation of a sample is a measure of the dispersion in a set of data, and that the standard deviation allows an assessment of how much the data points as a whole differ from the mean value.
Probability and Hypothesis Testing Be aware at its simplest level that probability is the chance of an event happening e.g. in a Triangle Test there is a 1/3 probability of choosing the ‘odd’ sample by chance.
Be aware that in hypothesis testing the ‘null hypothesis’ is what happens by chance while the ‘alternative hypothesis’ is an outcome that has a greater than chance probability of occurring.
Be aware that in hypothesis testing a conclusion is reached with a degree of confidence and thus attached to any outcome is a chance of being wrong i.e. a risk of rejecting the null hypotheses when it is true or accepting it when it is false.
State that concluding ‘no difference’ in a discrimination test does not imply the samples are the same.
State that to demonstrate similarity a much larger number of responses is required and a greater understanding of statistical principles will be needed.
RECOMMENDED TEXTS Guidelines for Sensory Analysis in Food Product Development and Quality Control. (2nd Ed.) Lyon, D.H., Francombe, M.A. and Hasdell, T.A. 2000.Chapman & Hall. ISBN 0-4124-2950-0
Sensory Evaluation: A Practical Handbook
Sarah Kemp, Tracey Hollowood, Joanne Hort.2009. Wiley-Blackwell. ISBN: 978-1-4051-6210-4
IFST GUIDELINES FOR ETHICAL AND PROFESSIONAL PRACTICES FOR THE SENSORY ANALYSIS OF FOODS