Introduction
Consumers want their food to be healthy but when it comes down to making a buying choice, it is taste that matters most. We experience the pleasure of eating, through our sense of sight, hearing, touch, smell, and taste. For example we appreciate the color of a ripe red apple (sight), we listen to the crunch of a cookie (hearing), we feel the texture of melting chocolate on our tongue (touch), we inhale the flavor of fresh strawberries as we chew (smell), and we taste the sharpness of sour lemons causing our face to cringe. Read more to learn about the sensory properties of food.
Taste and Flavor
Tasting is done with our tongue via taste receptors (gustatory cells) in our taste buds. Taste buds are located in the raised “bumps” on our tongue called papillae. There are only five types of taste receptors i.e. bitter, sweet, salty, sour, and umami. The umami receptor detects the amino acid glutamate, a chemical commonly found in meat and artificial flavors such as monosodium glutamate (MSG).
The “flavors” that our tongue normally gets credit for detecting are actually picked up by our olfactory system located in the nasal cavity. As we chew, odors travel via the back of our mouth to olfactory receptor cells which transmits the data to our olfactory nerve. From the olfactory nerve, the data is sent to our brain for interpretation.
Taste and flavor detection in the lab can be done by sensory evaluation (taste testing). However, instrumentation may also be used to increase objectivity. For example, sourness can be determined by measuring how much acid is present in the food by testing the pH with a pH meter. Sweetness can be determined by measuring brix (percentage sugar) with a refractometer. The saltiness of food brines can be determined by measuring specific gravity using a hydrometer or refractometer. When it comes to flavor detection, sophisticated methods such as gas chromatography are generally used.
Color
The color of foods adds to their attractiveness and appeal. Color is often used as a sign of freshness or spoilage. Subjective measurements of color may be done using a color scale. Objective measurements of color are done in the lab using a colorimeter. Using this instrument, color is reported in L*, a* and b* values where L* values indicate the degree of lightness from black to white (range = 0 – 100); a* values indicate color ranging from green to red; and b* values indicate colors from blue to yellow. In theory, there are no maximum values of a* and b*, but in practice, they are usually numbered from -128 to +127.
Texture
As we chew, we may experience such textures as crispiness, crunchiness, softness, stickiness, gumminess, and smoothness. The enjoyment of the food you are eating will depend on how much of each of these experiences you prefer for the given food. For example, you may prefer a crispy and crunchy cookie while others prefer their cookies soft.
Sensory Evaluation
While there are many objective instruments for getting a sense of the potential taste and flavor experience the consumer will have, nothing beats actually tasting the food Taste testing of food, also called sensory evaluation, is helpful in determining food quality, and providing information to inform quality control and product development. There are generally three types of sensory evaluation tests. These are hedonic, discrimination and descriptive tests. Hedonic tests are also called affective or likeness tests. These tests normally involve as many as 75-150 untrained sensory panelists with the goal to determine expected consumer acceptability. For example, you may have just developed a new chocolate strawberry jam and want to know how many people will actually like it. The results of the test will tell you if this product will eventually be successful in the market.
Discrimination tests are done to differentiate between characteristics of 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. For example, let’s say that the purpose of the sensory evaluation is to determine which product has less bitterness. In this case, during the screening, the potential taste panelists would be given a series of different concentrations of the bitter note that they would be tasting in the actual sensory evaluation if they’re selected. During the test, only those who were able to detect the bitter taste at even low concentrations would be selected to participate in the sensory evaluation. 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 can use this when you want to find out if consumers would be able to identify any difference with a new product you are developing. For example, let’s say that you have substituted a cheaper ingredient in the product and you want to know if customers will be able to pick up on this difference. You would give the panelists two samples that are just like the original product and one with the change. The panelists would then try to find out which one is different. If they are able to clearly identify the sample that’s different, you may need to improve the formula so that the difference is not obvious.
Duo-Trio Test: In this test, the panelists are asked to choose the sample that is the same as a reference sample. This could be used to determine if you were able to successfully replicate a product. Let’s say you are trying to copy your competitor’s product. You experiment with developing the new product and now you are pretty confident that consumers will not be able to tell the difference between yours and your competitor’s (the reference sample). The panelists would be given three samples to taste. One would be the competitor’s product (reference) and the other two would be versions of your product that you think comes close to your competitor’s. The panelists would be asked to tell which one of the product is the same as the reference.
Paired Comparison Test: In this test, the panelists are asked to compare two samples to tell the difference. For example, the objective could be to simply tell which one is sweeter, saltier etc. Let’s say that you increased the salt content of your product to help bring out other flavors, but you do not necessarily want the new product to taste too salty. In this test, the panelists would compare the original product with the new one to see if there is a noticeable difference in saltiness. If they can tell the difference, you probably added too much salt and would need to consider reformulating it.
Descriptive tests are done by trained panelists of about 8-12. 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 makes the evaluation as objective as possible. Food manufacturers who rely heavily on trained panelists include flavor ingredient producers and manufacturers of coffee, tea, and wine.
Suggestions for Sensory Evaluation Activities
- Label each sample with a random number code. Do not reveal brand names and other label information that could create bias
- Keep the noise in the room low to avoid distractions
- Ensure that the room is free from foreign odors
- Keep the preparation area separate from the tasting area
- Make sure that the tasting area is well lit and ventilated
- Use a room where you can control the temperature
- Keep sensory evaluation sheets simple and appropriate for the users (children, general public, trained panelists, untrained panelists etc.)
- Provide clear instructions to panelists in writing and orally before the test
- Communicate important reminders before the test e.g.
- Do not discuss your feelings about the taste of the samples with other panelists
- Taste samples in the order given
- Drink water and/or eat a cracker to clean their palate between samples
- Rinse mouth and expectorate (spit) if needed between samples
