Descriptive analysis is an important part of sensory evaluation. It provides information about the qualitative as well as the quantitative evaluation of food and it is widely used for obtaining detailed description about the aroma, flavour and overall texture of the food product

1. DESCRIPTIVE ANALYSIS
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Andrew L Myrthong
2014-12-126

2. 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 make comparisons between foods
– Affective Tests evaluate liking for foods. These are sometimes called
consumer tests
– Descriptive Tests describe the sensory attributes of a food
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3. Application of descriptive analysis
• The purpose of descriptive analysis is
to obtain detailed description of
– Aroma
– Flavour
– Oral texture
• It is used both to obtain qualitative
descriptors of the product and to
obtain quantitative evaluations of
product.
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4. Uses of descriptive analysis include
• Research and Development (long term studies)
• New product development
• Specifications for QA/QC purposes
• Define product attributes for consumer tests
• Track sensory changes over time
• Long term changes for shelf life/packaging studies
• Short term intensity measurement of specific attributes
• Measure attributes for comparison with instrumental/analytical measurements
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5. Qualitative aspects of descriptive
analysis
• Appearance characteristics
– Colour
– hue, chroma, uniformity, depth
– Surface texture
– shine, smoothness/roughness
– Size and shape
– dimensions, geometry
– Interactions among particles
– stickiness, agglomeration, loose particles
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6. • Aroma Characteristics
–Olfactory sensations
• vanilla, fruity, floral, skunky
• Nasal feelings
–cool, pungent
• Flavour characteristics
– Olfactory sensations
• vanilla, fruity, floral, chocolate, skunky, rancid
– Taste sensations
• salty, sweet, sour, bitter, umami (meatiness)
– Oral feeling factors
• heat, cool, burn, astringent, metallic
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7. • Oral texture characteristics
–Mechanical parameters - reaction of product to stress
• hardness, viscosity, deformation/fracturability
• Geometrical parameters - size, shape, orientation of
particles in product
–gritty, flaky, grainy, stringy
• Fat/moisture parameters - presence/release of fat, oil,
water
–oily, greasy, juicy, moist
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8. • Skin feel characteristics
–Mechanical parameters - reaction of product to stress
• thickness, ease to spread, slipperiness, denseness
–Geometrical parameters - size, shape and orientation of
particles
• gritty, foamy, flaky
–Fat/moisture parameters - presence/release of fat, oil, water
• greasy, oily, dry, wet
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9. 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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10. Training of panellists
• Reference scales are used to ensure consistency
between panellists across repeated evaluations
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11. Types of scale used
• Category scales
• Uses words to define intensity, such as "none", "just detectable",
"mild", "strong"
• terms chosen to describe (as far as possible) equal intervals - 9 point
scale most popular
• Line scales: mark a point on a line (typically 15 cm long)
• Magnitude estimation (ME) scales
• Free choice of first "score"
• Subsequent scores assigned in proportion
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12. Overall impression
• As well as rating individual attributes, some kind of "overall
rating" is sometimes needed. These may include
– Total intensity of aroma or flavour
– Balance/blend
– Overall difference
– Hedonic ratings
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13. 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
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14. 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)
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Hedonic ratings
• This is a rating of the overall acceptance
of a product
• It is not appropriate with trained panels
• Used only with consumer tests since
trained panels tend to weigh attributes
differently from ordinary consumers and
so their judgements are not "typical" of
consumer preferences

15. Common descriptive methods
A variety of procedures have been developed for descriptive testing.
These include
• Flavour profile
• Texture profile
• Quantitative descriptive analysis (QDA)
• Spectrum analysis
• Time-Intensity descriptive analysis
• Free choice profiling
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16. Flavour profile
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• Uses panel of 4 - 6 trained panellists
• Panel sit round table and evaluate one sample at a time and record
the ratings
• Panel then discusses ratings and arrives at a consensus
• Advantage of small panel
Disadvantages:
• Consensus method means
risk of bias from dominant
personality
• Danger of lack of consis-
tency and reproducibility

17. Texture profile
• Procedure similar to flavour profile, but a
wider range of scaling techniques may be
used
• Results may be by consensus method or
by statistical analysis
• Panel training involves understanding
underlying mechanical principles
• Experience of a wide range of textural
attributes
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18. Quantitative descriptive analysis
• Panelists develop agreed terminology beforehand
• Panelists evaluate products one at a time in separate booths
• Panellists are discouraged from discussing results afterwards
• Scoring is by marking on a line
• The results are analysed statistically
• Can lead to inconsistency of results
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19. Spectrum descriptive analysis
• Panelists score intensities with respect to learned absolute intensity scales
• A wide variety of standard descriptors are provided
• Scoring is both by use of descriptive terms and by marking on a line
• It is intended to provide consistent and reliable data by providing a wide
range of standards
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20. Time-intensity analysis
• Panelists evaluate intensity of an attribute at intervals over a period
• Time-intensity response curve is generated
• This should not be seen by the panelists while it is being generated
• Requires a well-trained panel to be effective
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21. Free-choice profiling
• Panelists are allowed to invent their own terms to describe
the sensory attributes of a set of samples
• Samples are from the same category of products
• Panelists develop their own scoresheets
• These are aimed at identifying terms that appear to
measure the same attribute
• Panel training requirements are minimal
• Panel is closer to a consumer panel
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22. Let Us Sum Up
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• The consumer acceptance of fruits/Vegetables and their products most often
relies upon the inherent flavor and textural quality of the product
• Incorporating sensory evaluation will help in the selling of a consumer
friendly product with increased acceptance
• When done properly, sensory information can provide reliable and useful
information about fruits and vegetables and their products which no
instrument can measure – their perceptual characteristics
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23. Thankyou
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