Color affects the judgment of food, the perception of freshness, the intensity of flavor, and the overall acceptability of food. Dubose, Cardello, and Maller (1980) have shown that one's attitude towards and one's choice of food is greatly influenced by its color. A person's first judgment of food is based on color, which then leads to the decision of whether or not to consume that particular food. In a study conducted by The Good Housekeeping Institute, 29% of their readership ranked good appearance or color as important in making a decision about a product, second only to freshness (Good Housekeeping, 1984).
Knowing that food coloring is important to consumers, psychologists such as Dubose et al. (1980) have conducted research and found that colors can affect a change in the flavor of a product. However, as Stillman (1993) points out, "The influence of color on flavor is interesting, because light reflected from a tastant does not directly influence any of the nerve fibers activated by the chemical and textural properties of food or drink" (Stillman, 1993, p 810). Nevertheless, there have been numerous studies that show that the occurrence of light waves bouncing off edible objects can in fact have a profound effect on how one tastes food stimuli. Alley and Alley (1998) show that specific coloring, color intensity and color-related expectations can modify the impact of color on taste. Clydesdale (1993) does specify that the effect of color on flavor most likely results from learned associations, rather than innate knowledge. Furthermore, color may be more prominent perceptually than flavor because color generates a stronger visual neural response than flavor generates a gustatory neural response (Oram, Laing, Hutchinson, Owen, Rose, Freeman, et al., 1995).
Solids and Liquids
When looking at how color influences taste, it is important to study if solids are perceived differently from liquids, or if cooler products are perceived differently from warmer products. A study conducted by DuBose et al. (1980) had participants rate the overall acceptability, color acceptability, flavor acceptability, and flavor intensity for 44 samples of liquid and solid stimuli. The experimenters tested 16 orange flavored beverages and 16 cherry flavored beverages. The food stimuli were 12 cake samples that were a combination of four yellow color levels, and three lemon flavor levels. The results showed that the perceived intensity in beverages increases as color increases for both the orange and the cherry beverages. This held true in the colored but flavorless samples where participants rated a more intense color as a more intense flavor as well, despite the fact that there was no flavor. This seems to also apply in solid samples where the perceived lemon taste increased when the yellow additive was increased (Dubose et al., 1980). This indicates that when tasting food products where color and flavor are both present, color may be the dominant influencer on the perception of taste. This experiment shows that the judgment of flavor intensity is directly affected by color level in both solid and liquid products. Clydesdale (1993) found the same results in fruit flavored beverages and cake as well.
These studies did not measure, however, if the same levels of sweetness were perceived differently between liquids and solids. Alley and Alley (1998) argue that liquids may produce more intense sensations than solids because liquids can cover more of the taste receptors faster and more thoroughly than solids can. The commercial world has taken this into consideration and added more sweeteners to solid sweets than to liquid sweets (Alley & Alley, 1998).
Temperature
Another factor that affects the color influence on flavor intensity is the temperature of the stimuli. Research has shown that cold temperature foods tend to decrease one's sensitivity to sucrose (Hyman, 1983). Additionally, taste sensitivity was prominently increased in low concentrations of sucrose as opposed to higher levels because "the various functions that relate perceived sweetness to concentration for various temperatures converged" (Bartoshuk, Rennert, Rodin, & Stevens, 1982). Since jellybeans are used in the current study, the sucrose level is high but they are tasted at room temperature; therefore, sensitivity should be relatively high.
Flavor Identification
Identification of flavors based on color has been tested to determine how well participants can identify flavors in a variety of color-flavor combinations. Specific color-flavor combinations have also been studied to determine how sweet the different colors are perceived to be. Various studies have shown that matched color flavor combinations are important in identifying flavors and are perceived to be more intense in flavor. Clydesdale's study (1993) showed that when colored food had matching color and flavor combinations they were perceived as having a stronger intensity than mismatched color flavor combinations (Clydesdale, 1993). Further, Oram et al. (1995) conducted research which showed that when beverages are color-masked or mismatched adults are worse at identifying the beverage's flavor. Additionally, the participants' identification is biased in the direction of the flavor that matches the color. In essence, if a participant is given a red-colored drink that contains some amount of grape flavoring, the participant is more likely to perceive that drink as some sort of red flavor (i.e. cherry) rather than a purple flavor. This bias is more evident when the flavor is less distinctive (Oram et al., 1995). Philipsen, Clydesdale, Griffin, & Stern (1995) also found that the absence of color could greatly reduce or eliminate one's ability to identify flavor. Furthermore, familiar food items may have a greater impact on the sensory judgment of color, resulting in greater intensities than non-familiar food items (Alley & Alley, 1998). In general, red colored food is perceived as sweet cherry or strawberry, yellow and green are perceived as sour/citrus tasting, and blue coloring is characteristic of sweet foods (Alley & Alley, 1998).
Taster Type
One area of taste perception that has yet to be considered as an influence of color on taste intensity is that of the different types of tasters. Research has shown that a person is a taster or a non-taster to certain bitter compounds, and that this status is inherited (Tepper, Christensen, & Cao, 2001). The bitterness of PROP probably follows an incomplete dominant pattern; non-tasters have 2 recessive alleles and perceive the least, super tasters probably have 2 dominant alleles and taste the most, while tasters probably have 1 dominant and 1 recessive allele and taste an intermediate degree (Bartoshuk, 2000). PROP (6-n-propylthiouracil) is a chemical relative to phenylthiocarbamide (PTC), which produces a bitter taste, and is used to determine taster type (Bartoshuk, Duffy, & Inglis, 1994). PROP is normally tested with NaCl as the control substance since NaCl intensity has been shown to remain stable across taster types (Bartoshuk et al., 1994; Tepper et al., 2001).
A person is defined as a taster or a non-taster by using the taste detection threshold for PROP (Ly & Drewnowksi, 2001). Research has shown that approximately seventy per cent of the US adult Caucasian population can taste PROP which categorizes them as tasters, while about thirty per cent cannot taste PROP, thus categorizing them as non-tasters (Tepper et al., 2001). Within the taster type there are also supertasters, who have a lower threshold (high sensitivity) for PROP, and regular tasters who have a higher threshold (lower sensitivity) for PROP (Drewnowski, Henderson, Shore, & Barratt-Fornell, 1997).
Tasters are also generally more sensitive than non-tasters to various compounds such as benzyl alcohol, caffeine, potassium chloride, sucrose, and saccharin (Tepper et al., 2001). However, the research is inconclusive as to whether or not the different taster types actually perceive sweet tastes differently (Drewnowski, Henderson, Shore, & Barratt-Fornell, 1997; Bartoshuk, 1979; Drewnowski, Henderson, & Barratt-Fornell, 1997; Ly & Drewnowski, 2001; Tepper et.al, 2001). The research which indicates that the taster types respond differentially to sweet stimuli do support that this is due to super-tasters' higher sensitivity to sucrose and saccharin water solutions than non-tasters (Drewnowski, et al., 1998)
Hypotheses
In the current study sixteen flavors and colors of jellybeans, half exotic and half typical flavors, will have different color intensities, to determine the effect color intensity has on flavor intensity between the taster types. Also, half of the participants will receive labeled jellybeans and half will receive unlabeled jellybeans. There are several hypotheses adopted in the present study. The first hypothesis states that the non-tasters will rate the jellybeans as lower in flavor intensity. The second hypothesis states that non-tasters will be more influenced by color-enhanced foods than super tasters, and thus will rate lighter and white colored jellybeans as less intense than they rate the medium or darker shades. Non-tasters will also be less likely to be able to determine the non-labeled jellybeans, while the super tasters will have a higher likelihood of correctly assigning a label. One general hypothesis is that all participants who receive labeled jellybeans will rate higher intensity than those that are given masked jellybeans.
Participants
Participants will be recruited from the SFASU student psychology pool using sign up sheets. There will be 96 participants with an age range of 18 years to 24 years. There will be a representation of ethnicity and an equal number of males and females in each taster type. Upon completion of the experiment each participant will be given a sample bag of Jelly Belly Jellybeans for their participation.
Materials
In accordance with Tepper's 2001 study, the taste stimulus used to determine taster status will be a solution of PROP with a concentration of .32 mmol/l and a solution of NaCl with a concentration of .1 mol/l. The solutions will be prepared in advance by dissolving the powder in spring water on mildly heated hot plate, and served at room temperature (Tepper et al., 2001).
A questionnaire and a pencil will be supplied with each sample. The questionnaire will ask the participants' name, whether the current sample is Solution 1 (PROP) or Solution 2 (NaCl) and the rating of the sample on the Green scale. The Green scale, developed by Green, Schaffer, & Gilmore (1993) will be used to determine the perceived intensity of the solutions. The Green scale is an adjective-labeled vertical line that has its upper limit as "strongest imaginable" taste and the lower limit is "barely detectable". The participant is to rate the intensity of the current taste compared with all other tastes found in daily life along this vertical line. Unlike other magnitude scales, the Green scale controls for ceiling effects by using the "strongest imaginable" adjective as the upper limit, thus not limiting one to a fixed number range (Bartoshuk, 2000).
A separate questionnaire will be used for tasting jellybeans. Questionnaires and a pencil will be provided on each desk for each individual participant. Every questionnaire will state the participants number (as explained in the procedure) and a sample number which corresponds to a number on the Dixie cup of each sample, as well as the Green scale for the participant to rate flavor intensity (as described on the previous page). The only difference in the questionnaires will be whether or not the flavor is stated on the questionnaire. The questionnaire for the non-labeled group will ask the participant to identify the flavor while the questionnaire for the labeled group will state the flavor of each sample.
White Dixie cups will be used to supply each participant with samples of the PROP and NaCl solutions, the jellybeans and spring water to drink between each sample.
Eight different colored and flavored Jelly Belly Jellybeans will be used as the taste stimuli. Table 1 shows the flavor/color combinations that will be used.
Table 1
Color Flavor Combinations
Color Typical Exotic Red Cherry Cinnamon Orange Orange Cantaloupe Yellow Lemon Banana Green Apple Watermelon Blue Blueberry Cotton
Candy Purple Grape Wild
Blackberry Pink Strawberry Bubble
Gum Black Licorice Chocolate
Pudding
First Day: Determining Taster Type
The experiment will take place over two days. The first day of the experiment will be used to determine taster type. Taster type will be determined using a method determined by Tepper et al. (2001) that uses one level of PROP and one level of NaCl. They have shown that this method is as effective in determining taster types as normally employed methods which use three levels of PROP (Tepper et al., 2001). The current study will use the same instructions as Tepper et al. (2001) shown below.
"You will rate the intensity of each solution by placing a mark on the labeled scale that best describes what you are experiencing. You can use any part of the line scale that seems appropriate for judging intensity. In making your judgments of intensity, you should rate the solution relative to the strength of all sensations you have experienced in your mouth in everyday life. Thus, 'strongest imaginable' refers to the most intense sensation you have experienced putting food and non-food items in your mouth. This includes such varied taste and mouth feel sensations that come from hot and cold foods an beverages, spices, and spicy foods, toothpaste, mouthwash, medicines etc (Tepper et al., 2001, p573)."
Spring water will be provided for each participant to rinse their mouth before the PROP and NaCl solutions. The participants will be told to place the entire sample in their mouths, expectorate the sample into an empty Dixie cup, and then rate its intensity on the Green scale. The participants will not swallow the sample as research has shown that saliva produced by food may have an effect on the taste and intensity perception of stimuli (Guinard, Zoumas-Morse & Walchak, C., 1997). Subjects will be given one sample at a time (to allow for time between samples), as well as water before each sample. Upon completion of tasting and rating both samples the participants will be asked to return the next day at the same time. Taster type will be determined by visually comparing the data (Tepper et al., 2001).
Second Day: Using Color Effect on Flavor Using Jellybeans
On the second day of the experiment each participant will be given a number based on his or her taster type (example: 1n1A: first non-taster in group 1 receiving order A). The participant will then be escorted to a partitioned desk that corresponds to their number. The participants will be divided into eight groups with four non-tasters, four tasters, and four supertasters in each group (see Table 2). Four groups will receive unlabeled jellybeans and four groups will receive labeled jellybeans. Each of these groups will then be divided so that one labeled and one unlabeled group will receive jellybeans that are either white, light colored, medium colored, or dark colored. Each of these 8 groups will receive eight differently colored jellybeans of which there will be four typical flavors and four exotic flavors that are red, orange, yellow, green, blue, purple, pink, or black. To ensure that not all participants receive jellybeans in the same flavor or color order the flavors and colors will be rotated within each group. In each group, two of each taster type will receive the flavors rotated between typical and exotic. However, one will begin with red typical jellybeans and progress through the colors as stated above towards black exotic jellybeans (Order A1) and the other will begin with a black typical jellybean and end with a red exotic jellybean (Order A2). The other two of each taster type will receive the flavors rotated between exotic and typical. One will begin with black exotic jellybeans and progress towards red typical jellybeans (Order B1), while the other will begin with a red exotic jellybean and end with a black exotic jellybean (Order B2) (See Table 3).
Table 2
Color Flavor Order and Group Assignments
One of each taster type receives one of the following within each group.
Order
A1 Order
A2 Order
B1 Order
B2 Cherry Licorice Chocolate
Pudding Cinnamon Cantaloupe Bubble
Gum Strawberry Orange Lemon Grape Wild
Blackberry Banana Watermelon Cotton
Candy Blueberry Apple Blueberry Apple Watermelon Cotton
Candy Wild
Blackberry Banana Lemon Grape Strawberry Orange Cantaloupe Bubble
Gum Chocolate
Pudding Cinnamon Cherry Licorice
Table 3
The Groups will be assigned as follows (4 of each taster type per group):
Group
1 Group
2 Group
3 Group
4 Labeled Labeled Labeled Labeled White Light
Colored Regular
Colored Dark
Colored Group
5 Group
6 Group
7 Group
8 Unlabeled Unlabeled Unlabeled Unlabeled White Light
Colored Regular
Colored Dark
Colored
When all participants have been seated they will be given a consent form to read and sign, as well as a demographic form to complete. All participants will be told the same directions as a group. The directions will be as follows:
"You will taste different flavors of jellybeans. Simply chew the jellybean, but do not swallow it. Spit it back into the Dixie cup when you are finished, and then take a drink of water from the other Dixie cup. You will be given 1 jellybean at a time and a cup of water with each sample. Be sure to drink the water between each sample. You will also be given a form that asks relevant questions pertaining to the sample. I will collect both cups and the form after each sample. Please proceed at your own pace. Any questions?"
Again, to reduce the effect saliva has on taste and intensity perception, the participants will not swallow the sample (Guinard, Zoumas-Morse & Walchak, C., 1997).
The participants will be given one cup of water to drink before the first sample is given. Each participant will be given samples of jellybeans one at a time, as determined by their group, a cup of water to drink after the sample is rated, and the questionnaire. The groups given labeled jellybeans will rate the flavor accuracy and the intensity level, while the groups given unlabeled jellybeans will determine the flavor and rate the intensity of flavor. After each sample is completed the next sample will be distributed individually by the experimenter. Upon completion of the eight samples the experiment will be finished, and the participant will receive a sample bag of Jelly Belly Jellybeans for their participation.
Results will be analyzed using a 4(color intensity) X 3 (taster type) X 2 (flavor type) X 2 (label) between subjects ANOVA. The color intensities are white, light colored, medium colored, and dark colored. The taster types are non-taster, taster, and super-taster. The flavor types are defined as typical or exotic flavors. These two flavor types were used to ensure the results were similar across the two types. No hypotheses were stated and thus no results are concluded for this variable, as it was used to diminish confounding effects. The last independent variable is whether the jellybean is labeled or not labeled with the jelly bean flavor. The two dependent variables are the individual ratings of intensity measured in the number of centimeters from the x-axis where the maximum is 100 cm, and the number of correct labels of unidentified stimuli.
The hypotheses stated for the current study will be supported. Non-tasters will rate the intensity of the jellybeans (M = 32.5) much lower than the tasters (M = 55.75) or the supertasters (M = 63.5). In general, this may be due to the idea that non-tasters have less sensitivity to certain taste, thus this may influence how the non-tasters perceive the sweet taste of the jellybeans. If a certain compound is not tasted, then the entire stimuli can be distorted. Supertasters have the ability to taste a variety of compounds and thus the flavor of the stimuli will be complete, giving rise to a higher intensity. Complete taste versus incomplete taste may influence the way in which these two taster types perceive stimuli.
The hypothesis that non-tasters rate lighter shades of jellybeans as less intense than darker shades more so than do tasters or super-tasters will also be supported. Again, this may be due to the idea that non-tasters do not taste as many compounds as tasters do. Thus, non-tasters may use their visual system to aid in determining the intensity of the stimuli. Therefore, a non-taster will perceive a lighter colored jellybean as less intense than the tasters will because their visual system perceives less intensity.
Further, once intensity reaches a certain level very little can actually have a significant impact on intensity. In this case, super-tasters already have a higher sensitivity to certain foods so they will be less influenced by the colors of the jellybeans. However, since non-tasters have a much lower intensity rating they are more vulnerable to outside influences on taste, such as color.
The hypothesis that non-tasters will have less ability to determine the non-labeled jellybeans, while the super tasters will have a higher likelihood of assigning a correct label will also be supported. Since non-tasters do not perceive all the compounds tasters perceive, their ability to correctly label unidentified stimuli is decreased. The results will show that non-tasters labeled the jellybeans incorrect more often than tasters or super-tasters did. When one does not receive all the information possible for an unidentified stimulus, the ability to label that stimulus specifically may be hindered. Therefore, the result that non-tasters will not able to correctly identify as many stimuli as tasters is reasonable.
Across all subjects the labeled jellybeans received higher intensity ratings than non-labeled jellybeans. This is in accordance with past research which indicates that unlabeled stimuli have lower intensity ratings because humans have a difficult time identifying taste when no color is present (Clydesdale, 1993; Oram et al., 1993; Philipsen, et al., 1995). When both color and taste are present, visual and taste receptors are both activated suggesting that more sense receptors are activated and therefore provide more information to the brain. When the brain has more information it can utilize top-down processing to assess the current situation.
In conclusion, past research on the influence of color on taste perception has been extensive. However, the current study is able to assess whether different taster types will be differentially influenced by various shades of colors for the same flavor. In essence, non-tasters should more influenced by color than super tasters, and are less able to identify the flavor when the jellybean was not labeled. Additionally, the non-labeled jellybeans will be rated as less intense than the labeled jellybeans. Outside of the lab this in turn suggests that food manufacturers need to increase colorants so that the foods appear more intense to ensure that taste intensity levels are fairly even across taster types. Additionally, specific labeling of flavors will increase the intensity of the flavor. This research produces a greater understanding of the impact of physical state and color on the judgment of foods and beverages. Thus, it is beneficial in improving food products, and allows psychologists a better understanding of how sense receptors influence perception.
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