Sensory evaluation

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Sensory evaluation
DRAFT ONLY
Foundation
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Learning objectives

• To know the purpose of sensory evaluation.
• To understand the difference between trained and
  untrained testors.
• To know which senses are used in sensory
  evaluation.
• To understand how sensory tests are used.
• To know the different tests commonly used in the
  food industry.

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What is sensory evaluation?
Sensory evaluation involves using one or more
tests to assess different characteristics of food
such as taste, odour and texture. The
tasters look at, smell and eat food samples,
then record their opinions. Depending on the
needs of the food producer, tasters may or may
not have been specially trained and their numbers
may vary.
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Trained testers
Trained testers can detect minor differences
between products or assess specific attributes of
a product. To make sure that the results are
not biased in any way, testing is carried out
under controlled conditions. Testing usually
occurs in booths free from cooking smells with
controlled lighting and heating.
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The controlled environment

• Trained testors taste samples of the same size,
  served on identical plain white dishes, coded
  with random numbers.
• The temperature of the samples is controlled.
• Drinking water and cream crackers are often
  supplied to cleanse the palate between samples.
• This will ensure the tasters are not distracted
  or influenced by any means and a fair test is
  conducted.

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Untrained testers

• These are often consumers, and are invited to
  test products as part of a consumer panel, or use
  them at home.
• They give general information about which
  product they prefer, or comment on certain
  characteristics, for example the savoury taste
  of a pasta dish for slimmers.

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Untrained testors

• Untrained testor panels are balanced by age, sex
  and ethnic background.
• Sometimes particular types of people are used in
  consumer panels, for example people who are on a
  vegetarian or on a slimming diet.

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Hearing
What senses are used? The tasters focus on one
attribute, for example taste or appearance, at a
time, and record their responses on paper or
directly on to a computer.
Hearing sometimes a product is associated with
a sound the crunch of a potato crisp crackle of
a breakfast cereal.
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Sensory evaluation

• Smell and taste the tongue detects five basic
  tastes sweet, sour, salt, bitter and umami.
• The nose detects the volatile aromas released
  from food which produce the sensations of flavour
  in the mouth. The senses of smell and taste work
  together.
• A person who has a bad cold, or holds the end of
  their nose, may not be able to detect different
  flavours very well.

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Sensory evaluation
Touch when food is placed in the mouth, the
surface of the tongue and other areas of
sensitive skin in the mouth react to the feel of
the surface of the food. Different sensations are
felt as the food is chewed and becomes broken up,
such as when a crusty bread roll becomes soggy
with saliva.
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Sensory evaluation
Sight the appearance of food can make it more
or less appetising. The size, shape, colour,
surface texture and presentation are all
important factors when a consumer is deciding
whether to purchase or eat a product. The
lighting in sensory booths is often changed to
disguise the colour of a product, so that the
visual properties can be assessed.
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Industrial use of evaluation

• Sensory evaluation is an important technique for
  use by companies developing new products or
  checking the quality of existing ones. Sensory
  evaluation can be used to
• distinguish between products, e.g. lower fat
  compared with traditional products
• test the popularity of products
• describe specific product attributes e.g.
  crunchiness
• maintain consistent uniform product quality
• profile the characteristics of a modified
  product against those of an original product.

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Industrial use of evaluation

• assess whether a new product is likely to be
  acceptable to, or popular with consumers
• carry out quality control, monitoring samples
  from the production line against the original
  specification
• measure shelf life by testing samples at
  known periods after production to see how eating
  quality is affected
• monitor prototypes, checking that the
  specification or improvements are being met.

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What sensory tests are used?
There is a set of standard tests which can be
used by industry. These were established by the
British Standard (BS5929). They include
Preference tests These supply information on
peoples likes or dislikes of a product. They
are not intended to evaluate specific
characteristics , such as crunchiness or
smoothness. They are subjective tests.
Discrimination tests These aim to evaluate
specific attributes, i.e. characteristics of
products. They are objective tests.
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Preference tests

• There are three different types of preference
  tests, pair comparisons, ranking and hedonic
  scale tests.
• Paired comparison
• This is where tasters are asked to state which
  of two samples they prefer.
• Ranking
• Tasters are asked to rank in order of preference
  a range of similar products.

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Preference tests

• Hedonic
• Products are scored on a 5 or 9 point scale
  according to the degree of liking of a products
  sensory and overall appeal.
• Comments are also recorded.
• The hedonic test should not be used to evaluate
  quality or specific product attributes as it is
  only suitable for gauging preferences.

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Discrimination tests
Paired comparison This is where tasters are
asked to compare two samples, for a specific
characteristic, e.g. fruitiness Ranking This
is where tasters rank samples in order for a
specific characteristic, e.g. sweetness.
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Test results

• Scoring tests using scales samples can be
  scored on different scales to evaluate different
  characteristics.
• Profiling is another method of showing test
  results.
• Either a different grid is used for each sample,
  or a number of results are plotted onto one grid,
  with a key.
• The grids are often referred to as profiles or
  star diagrams.
• This method of evaluation tends to use highly
  trained tasters.

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Review of the learning objectives

• To know the purpose of sensory evaluation.
• To understand the difference between trained and
  untrained testors.
• To know which senses are used in sensory
  evaluation.
• To understand how sensory tests are used.
• To know the different tests commonly used in the
  food industry.

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For more information visit www.nutrition.org.u
k www.foodafactoflife.org.uk