Transcript DRAFT ONLY Sensory evaluation © Food – a fact of life 2009 Foundation.

DRAFT ONLY
Sensory evaluation
© Food – a fact of life 2009
Foundation
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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 people’s 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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
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.
© Food – a fact of life 2009
For more information visit
www.nutrition.org.uk
www.foodafactoflife.org.uk
© Food – a fact of life 2009