DRAFT ONLY Sensory evaluation 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Preference tests • Hedonic Productsare 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.
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.
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.
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.
For more information visit www.nutrition.org.ukwww.foodafactoflife.org.uk