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Descriptive Sensory Analysis

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Introduction

Descriptive analysis is concerned with trying to provide description of the sensory qualities of food. It is one of three basic types of sensory test

Difference Tests are usually quantitative, whereas descriptive and affective tests can be qualitative or quantitative and involve detection and description of both Qualitative and Quantitative sensory attributes

Qualitative aspects of foods include

Difference test panels should be able to detect and describe sensory aspects of a product, differentiate and rate the intensity of each attribute and define the degree to which each attribute is present. This requires use of trained panels

Panel size may vary widely: 5 - 100 judges with small panels being sufficient for grocery products. For mass produced products such as beer, soft drinks, confectionery where small differences can be important, large panels are usually necessary.


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Application of descriptive analysis

The purpose of descriptive analysis is to obtain detailed description of

of foods for a range of purposes. It is used both to obtain qualitative descriptors of the product and to obtain quantitative evaluations of product.

Uses of descriptive analysis include


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Qualitative aspects of descriptive analysis

Perceived sensory parameters which define the product are referred to variously as; attributes, characteristics, character notes, descriptive terms, descriptors. The terms used should define the sensory profile, picture or thumbprint of the product. Training of panellists is essential to ensure consistent descriptions of attributes

Descriptive profiles

The range of qualitative characteristics from which a selection may be made for particular purposes are indicated below

Examples are given of some of the descriptive terms that may be used and in which training is needed

  1. Appearance characteristics
  2. Aroma Characteristics
  3. Flavour characteristics
  4. Oral texture characteristics
  5. Geometrical parameters - size, shape, orientation of particles in product
  6. Fat/moisture parameters - presence/release of fat, oil, water
  7. Skinfeel characteristics

Key aspects of qualitative descriptive analysis

Sensory terms are based on an understanding of technical and physiological principles. Panellists are trained to fully understand the terms and to use them consistently. references for terminology are used to ensure consistency. These define characteristics with respect to "model" food products displaying the characteristic


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Quantitative aspects of descriptive analysis

The quantitative aspect or intensity expresses the degree to which a characteristic is present and is expressed by assigning a value on a scale. The validity and reliability of the analysis is dependant on the selection of scaling technique which should encompass full range of intensities but be sufficiently sensitive to pick up small differences


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Training of panellists

Reference scales are used to ensure consistency between panellists across repeated evaluations

Types of scale used

Order of appearance of sensory attributes

In addition to qualitative and quantitative aspects, the order that attributes appear can sometimes be detected. This can sometimes be manipulated by the protocols used eg with texture analysis. In other cases, especially with chemical senses (flavour,aroma), the order can form part of the product profile. Important in some cases is the lingering of an "aftertaste" or an "afterfeel"

Overall impression

As well as rating individual attributes, some kind of "overall rating" is sometimes needed. These may include

Total intensity of aroma/flavour

Overal intensity of aroma or flavour is an assessment of the overall impact the product will have on the consumer

Balance/blend (amplitude)

This is an assessment of the way the various flavour or aroma characteristics fit together in the product. It requires highly trained and skilled panel members and is not appropriate with all products

Overall difference

In some situations, relative difference between samples and controls is important. This involves a quantifying of the difference from the control (c.f. Duo trio test)

Hedonic ratings

This is a rating of the overall acceptance of a product. It is not appropriate with trained panels and should only be used with consumer tests since trained panels tend to weigh attributes differently from ordinary consumers and so their judgements are not "typical" of consumer preferences


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Common descriptive methods

A variety of procedures have been developed for descriptive testing. These include

Each of these is briefly described below


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Flavour profile


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Texture profile


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Quantitative descriptive analysis


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Spectrum descriptive analysis


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Time-intensity analysis


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Free-choice profiling

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