Genetics in Taste
Perception
Addison McLeod
Biology Lab 102: Section 009
Keith Fuller
October 19, 2017
Abstract
A universally known fact is that humans are required to ingest food in order to live (Schumpert, 2017). Although this is widely eminent, humans also display considerable differences in taste sensitivity to different substances (Drayna, 2005). Genes, along with your surroundings, can affect how you perceive taste, in terms of spicy or sweet, hot or cold. These differences could be due to the origin of a person (Drayna, 2017). Before this experiment was conducted, it was hypothesized that if students’ parents preferred spicy foods more than sweet foods, then the students will be more likely to taste, or assess, the foods more acutely, because the student has grown up around spicier foods. During the experiment, each member of the group tasted each food and rated it either on the bitter-sweet scale of 1-10, 1 being extremely sweet and 10 being extremely bitter, or the hot-cold scale, 1 being extremely cold and 10 being extremely hot (Schumpert, 2017). After the foods were evaluated, the results were recorded and the hypotheses proved to be correct.
Introduction
Humans display considerable differences in taste sensitivity to different substances (Drayna, 2005). These differences could be due to genetics in origin, or other differences that could result in the variation of taste sensitivity (Drayna, 2005). Looking further into the genetics behind taste perception, studies have been conducted to try to understand taste at a molecular level by assessing genes that can be classified for contributions to phenotypic dissimilarities in taste abilities (Drayna, 2005). This concept has given a better comprehension of the ability to taste phenylthiocarbamide (PTC) that has concluded the debate of the genetics of this classic human trait (Drayna, 2005). There is a particular coding sequence that must be present in the taste receptor genes, which implies that PTC tasting demonstrates more general taste sensory variation (Drayna, 2005). Many facets of taste perception still continue to be inadequately characterized, though (Drayna, 2005). However, more general studies of the connection between genetics and taste phenotypes reveal genes encoding proteins that were formerly unknown to be involved in the sensory process of taste (Drayna, 2005).
Hypotheses
Hypothesis one of the experiment was stated as such: if the students’ parents prefer spicy foods more than sweet foods, then they will be more likely to assess spicy foods more acutely than sweet foods because they will have grown up around spicy foods. (Sweet foods would be perceived by these students as extremely sweet compared to someone who prefers sweet foods over spicy). Hypothesis two of this experiment was given as: If students’ parents prefer more salty/spicy foods than sweet, then they will be more likely to taste hotter foods more acutely than “colder” or minty foods because they grew up eating spicy foods.
Materials and Methods
In the Genetics of Taste and Perception Lab, different tastes were examined and how each group member distinguished them. The materials used for the first taste test were control test strips, which do not contain any chemicals but act as the control in taste test experiments. Next, PTC test strips, sodium benzoate strips, and theorem test strips were tasted. To taste the control test strip, a small sheet was torn off the control strip and then each group member placed it on their tongue for five seconds, with no expectations of flavor in order to calibrate taste anticipations. Next, the test strip was removed and each group member moved their tongue back and forth in their mouth, then repeated the process with that same strip (Schumpert, 2017). This method was repeated for all other strips (Schumpert, 2017). After the results were recorded from tasting each of these strips, the next part of the experiment was food tasting (Schumpert, 2017). For bitter tastes, ginseng candy, root beer candy, dark chocolate, coffee, and pickles were tested. For sweet tastes, sugar, milk chocolate, jolly ranchers, sour patch kids, and brown sugar were used. For spicy foods, horseradish, Tabasco, ketchup, wasabi, and cinnamon candy were sampled. And finally, for cold tastes, peppermint candy, an icebreaker, spearmint candy, and wintergreen candy were tasted. In order for the results to prove the hypothesis, the students’ whose parents preferred spicy food compared to sweet foods would be more like to taste a spicy food, wasabi for example, at a more acute level than someone who preferred sweet foods. Following each tasting, the students documented their results and then compared their ratings with each hypothesis. If the hypotheses described beforehand were correct, then the students who claimed their parents preferred spicy foods would have evaluated the sweet foods as extremely sweet, compared to spicy foods, which they should rate at a middle number on the scale.
Results
Spicy Jessica Morgan Bailey Addison Lauren Essence
horseradish 5 7 7 7 7 7
tabasco 6 10 8 10 6 7
ketchup 5 5 5 5 5 5
wasabi 6 8 8 8 7 10
cinnamon 5 7 5 7 5 5
The results from this experiment were categorized as such: each member of the group tasted each food and rated it either on the bitter-sweet scale of 1-10, 1 being extremely sweet and 10 being extremely bitter, or the hot-cold scale, 1 being extremely cold and 10 being extremely hot (Schumpert, 2017). Although the evaluations somewhat correlated with the first hypothesis, the type of food, however, varied as shown in the results.
Table 1: Results from testing spicy foods. Students who preferred this type of food are highlighted in yellow.
Sweet Jessica Morgan Bailey Addison Lauren Essence
sugar 5 3 3 3 2 2
milk chocolate 4 4 1 3 3 2
jolly rancher 3 2 4 4 3 3
sour patch kids 1 2 4 4 2 1
brown sugar 3 2 4 2 2 4
Table 2: Results from tasting sweet foods. Like Table 1, Students who claimed to prefer spicy foods are highlighted in yellow.
Cold Jessica Morgan Bailey Addison Lauren Essence
peppermint 5 5 5 5 3 5
icebreaker 4 2 4 3 4 2
spearmint 5 3 3 4 3 4
wintergreen 5 4 4 3 2 3
Table 3: Results from testing cold tastes.
For each table, the results are around the same number. The table that represents the judgment of the spicy foods, however, seem to fluctuate a little more than the rest. The graph shown below is a representation of the numbers that accompany each food tested with the people who like spicy food with the people who do not. Graph 1: Results from Table 1.
Discussion
After looking at the results of the experiment, the hypotheses proved to be true. Although each member tested the same kind of food, not everyone would have the same perception of the taste. For example, in Table 1, it shows the rating of horseradish, Tabasco, ketchup, wasabi, and cinnamon. Though horseradish and ketchup have relatively the same numbers, the assessment of wasabi, cinnamon, and tabasco correlate with the first hypothesis. The students who had said prior to the experiment that their parents favor spicy foods had evaluated these three foods at a lower number, meaning it was less spicy to them than the two students whose parents did not favor spicy foods, who had rated the three foods higher on the scale. The data from Table 2 supports the previously stated hypotheses, as well. When testing sweet foods such as sugar, milk chocolate, jolly rancher, sour patch kids, and brown sugar, the students who prefer spicy foods rated the sweet foods lower on the scale, implicating the foods were very or extremely sweet to them, compared to the students who did not prefer spicy food, who rated the sweet foods higher on the scale. In terms of flaws or weaknesses of this experiment, there could have been flaws in the amount of food that was to be tested. With four groups, it was hard to get enough samples so that each member of one group could get a taste. In light of this inconvenience, though, the data collected from the experiment proves the overall hypotheses. Whether or not the perception of these foods has to do with the environment around a person or the genetics of a person, will have to have a further investigation before determining either theory.
References
Drayna D. 2005. Human taste genetics. Annu Rev Genom Hum Genet. 6:217-35.
Schumpert, Andy. 2017. Journal of BIOL102L.1-14.