Sensory testing has been taking place ever since there has been humans around to assess the quality of their surroundings. The history of sensory analysis began during war time when there was an aim to make palatable food for the armed forces. Sensory testing places worth on a product and helps to determine its acceptability in the marketplace. Research, product development, and quality control are three main areas that sensory testing is utilized (Meilgaard et.al., 1991).
There are many kinds of tests that are given to evaluate sensory perceptions of a product. Difference testing is one of the tests that are used in sensory evaluation. There are many varieties of Difference Tests. Triangle or Duo-trio Tests can measure the overall difference between two products. Ranking, Paired Comparison, and many other types of multiple comparison tests can isolate attribute differences within a product (Meilgaard et.al., 1991).
People go through a particular process during a sensory experience. First there needs to be some type of stimulus which creates some kind of sensory sensation. After a sensation has occurred, the nerves in that area of the body send signals to the brain creating a perception of the experience. Messages are sent back from the brain to various body sites to respond to the stimulus (Meilgaard et.al., 1991). For example, someone takes a bite of hot pizza (stimulus). The nerves in their mouth detect the hot cheese and send a message to the brain that there is something very hot in their mouth (sensation). The brain perceives the cheese to be hot (perception), so hot they cannot keep it in their mouth and they respond by spitting the bite of pizza out (response). Another response would have been that they perceived the cheese to be hot, but not hot enough to spit it out, and they respond by chewing and swallowing the bite of pizza.
Since the main focus of food preparation is for consumption purposes, it must create an acceptable sensory experience. Through sensory testing,"acceptability" is determined. As new food products are created and put on the market, it is important to know what the consumers desires. Consumers and producers may have totally different ideas about what a product should be. Consumer testing during product development provides crucial information a company needs to be successful (Bennion, 1995).
For all testing, excluding consumer testing, it is critical to select an appropriate panel. Often training needs to take place so that the same kind of information is being selected and that similar vocabulary is being used to describe the sensory experience. It is important to use three-digit random codes on your samples to avoid any biases. In choosing a panel, make sure to have a random representative sample of the population. For further information on panelists selection see: http://oregonstate.edu/instruct/nfm405/gina.html panelist selection.
There are four basic methods of sensory evaluation. Firstly, analytical or discriminatory testing, which determine whether or not a deffernce exits between samples, hence Difference Tests. Secondly, there are descriptive tests used to determine the nature and intensity of attributes in a sample. Rating tests are often used to determine this information. Thirdly, there are preference or acceptance test. A hedonic scale is common in this type of testing. Lastly, there are test to measure sensitivity. Test that monitor the detection and thresholds to a stimulus are utilized here (Heath, 1981).
There are many types of Difference Test. A Triangle Test is a sensory test that is used to determine difference between products. These differences could be ingredients, processing, or differences in packaging. Effective testing includes presenting three samples and asking which sample is different. In any type of test, leaving room for panelists to make comments is also beneficial because it can sometimes better explain their choices. A Two-out-of-Five test is similar to the Triangle Test. Panelists are asked to pick two out of the five that are similar in characteristics (Meilgaard et. al., 1991).
Multiple Paired Comparison Tests, where panelists are asked to taste two samples and rate attributes such as saltiness. The panelists may be asked to mark the sample that is the most or least salty. This test involves a number sample pairs.
In a ranking test, panelists are asked to rank in order an attribute the sample possesses (or lack of.) Ranking samples of apples on levels of crispiness (most crisp to mushy) is an example of a ranking test. Ranking the color brown on various types of french fries after being deep fat fried (using different types of potatoes may cause intensity changes to occur in the browning of the potato) is another example of a Difference Ranking Test.
These are just a few of the numerous types of Difference Tests that are used in sensory evaluation. Results of such tests are often displayed in tables and graphs to help organize information and make it more meaningful to readers. Sensory testing is crucial to be successful and to make the most out of the resources available.
