Objective: To evaluate foods based on their sensory attributes
Background: We experience food using our sense of sight, touch, hearing, smell and taste. While there are many instruments that can help us evaluate and estimate these sensations, nothing beats tasting and experiencing the food ourselves. We do this through a systematic process called sensory evaluation. In this process, individuals taste the food and provide feedback about what they experienced. That feedback is collected and analyzed by a food scientist or sensory scientist to understand and interpret what the tasters are saying. Sensory evaluation may be in the form of a hedonic, discrimination or descriptive tests.
Hedonic tests are also called affective or likeness tests. These tests normally involve as many as 75-150 untrained tasters (also called sensory panelists) with the goal to determine the expected consumer acceptability. For example, let’s say you just developed a new chocolate strawberry jam and want to know how many people will like it. The results of this test will tell you if the product will eventually be successful in the market.
Discrimination tests are done to differentiate between different food samples. The test usually involves 25-50 untrained panelists who had been previously screened to select only those who have a keen sense of sensory perception. In other words, you must be a good taster to participate. There are three types of discrimination tests; triangle test, duo-trio test, and paired comparison test.
- Triangle Test: In this test, taste panelists are asked to choose the sample that is most different. You could use this test when you want to find out if consumers would be able to identify any difference with a new product you are developing. For example, if you substituted a cheaper ingredient in the product, you may want to know if customers will be able to pick up on this difference. The panelists would normally be given three samples to taste. Two would be alike and one different. They would be asked to pick out the one that is different.
- Duo-Trio Test: In this test, the panelists are asked to choose the sample that is the same as a reference sample. Imagine that you think you’ve successfully copied a competitor’s product. To determine success, you would present two versions of your product to the panelists and your competitor’s product (the reference sample). The panelists would be asked to pick out which one is the same as the reference sample.
- Paired Comparison Test: In this test, the panelists are asked to compare two samples in order to tell the difference between them. For example, which one is sweeter?
Descriptive tests are done by trained panelists of about 8-12 people. The training is necessary to “calibrate” each panelist so that they share similar feelings on the intensity of the taste or flavor that they are looking for. This is like calibrating an instrument. The only difference is that in this case, the instruments are humans. Food manufacturers who rely heavily on trained panelists include flavor ingredient producers and manufacturers of coffee, tea, and wine.
In this lab, you will be the Sensory Scientist conducting a test to determine which type of potato chips is most acceptable. Feel free to substitute potato chips for three different brands of another snack. You will need at least two taste testers in this experiment. They don’t have to do the test at the same time if that is not possible for you.
Materials and Equipment
- Three different brands of potato chips
- Disposable cups and plates
- Water (at room temperature)
- Sensory evaluation sheet
- Pens or pencils
- Label three small paper plates (or other plates you have available, as long as they are the same size and style) with the following 3-number codes
- Transfer the potato chips to corresponding plates. Make a note of which brand correspond to which code. This is very important when the time comes for you to analyze and interpret your data. Do not allow the taste testers to see the packages.
- Present the samples to the tasters in random order i.e. not the same order. For example,
- Taster 1: 397, 658, 428
- Taster 2: 658, 428, 397
- Taster 3: 428, 658, 397
- Also present each taster with an evaluation sheet and pen/pencil, a cup of room temperature water and plain crackers (optional) to clean their palate between each taste
- Start the sensory evaluation by explaining the procedure and providing useful tips e.g. let them know:
- What they will be tasting
- The purpose of the exercise (To determine which chips they prefer. You can also explain that this is for your Biology of Food Class. I am sure they will want to help you out)
- How to complete the evaluation form (see form at the end of this document)
- Any allergens present in the food they will be tasting (the 8 food allergens are: soy, milk, egg, peanut, tree nut, fish, shellfish and wheat). Check this ahead of time by looking at the package ingredient label. Excuse them from the activity if they are allergic to any of the ingredients.
- The importance of rinsing mouth with water (or eating a plain cracker) before and after each taste and resting between each taste for 30 seconds (These instructions are also on the evaluation form)
- Allow the taster to taste the samples. Make sure to be quiet while they are tasting. Don’t engage them in conversation during the activity
- When they are finished, collect the completed forms and thank them for participating (Consider giving them a treat e.g. chocolate, fruit or snack for participating)
- Average the scores collected and use excel to create a bar graph showing Likeness on the y axis and the code numbers on the x-axis. Hint: Each response represents a number from 1 (dislike extremely) to 9 (like extremely) (5 points)
- Which product brand received the highest overall score (1 point)
- What do you think is special about this brand that distinguishes it from the other two? (1 point)
- Name the type of sensory evaluation test used in this activity (2 points)
- Critical thinking question: Why do you think you were told to give the tasters the samples in random order rather than have each of them taste the samples in the same order? (3 points)
Sensory Evaluation Sheet
- Record the sample codes in the order in which they are given
- Rinse your mouth by drinking the room temperature water provided
- Taste each sample in the order in which it is given (eat a plain cracker and rinse your mouth by drinking room temperature water between each sample)
- Complete the table indicating your likeness for each sample
|Scale||Code __________||Code __________||Code __________|
|Like very much|
|Neither like nor dislike|
|Dislike very much|