1. Why does food taste less delicious when you keep eating the same thing?
Imagine eating your favorite snack one by one. The first bite feels wonderful, but by the tenth bite, the flavor may feel less intense. This is not just because your stomach is full. The "pleasantness" you feel from a food’s taste, look, and smell drops while you are eating it. The pleasantness of other foods you have not eaten yet also drops, but the drop is larger for the food you are currently eating. In a 1982 paper by Rolls and colleagues, this phenomenon was named "sensory-specific satiety" [1]. The word "specific" means "limited to that food." It shows that boredom with a specific taste progresses separately from general fullness.
2. How did changing a sandwich filling to four types lead to 33% more eating?
What happens to the amount of food eaten if you change the flavor? The same paper describes a lunch experiment comparing sandwiches eaten with only one filling versus sandwiches served with four different fillings in sequence [1]. The result showed that people ate 33% more when the fillings were changed. A 33% increase means that if someone would normally eat 300 g, they would eat about 400 g. When researchers changed only the shape of pasta or only the flavor of a dish, people ate about 14–15% more in both cases. This shows that changes in shape or flavor, not just taste, can increase the amount eaten [1]. The way we get used to a taste also depends on the type of taste. In a study of sweetened yogurt, the intensity of sweetness dropped over time, but the intensity of sourness did not drop [2]. It seems that we do not adapt to all aspects of a flavor equally with every bite.
3. Why is sushi ginger eaten between bites instead of placed on top?
At a sushi restaurant, people rarely put ginger on top of their sushi. Ginger is used as a palate cleanser, eaten between bites to refresh the mouth [3]. It is made from young ginger sliced thin and pickled in sweet vinegar. One theory says the name comes from the "gari-gari" sound it makes when chewed. It was originally a term used in the sushi industry [3]. Does a palate cleanser erase the previous taste, or does it change the aftertaste? Few studies have tested this directly, but one experiment offers a hint. In a study with 36 participants, using a mouthwash with menthol increased sensations of "cold," "mint," and "tingling" in the aftertaste. This reduced the desire to eat potato chips and the liking for them. The amount eaten over 12 minutes dropped by 29%. Rinsing with water showed no clear change in the amount eaten or appetite ratings [4]. However, this result is from just one study on mint mouthwash. We cannot say for sure that ginger or wasabi cause the same effect.
4. How does wasabi's heat act on the body's pain and irritation sensors?
Many people have teared up from eating too much wasabi. The spicy component of wasabi is volatile mustard oil (isothiocyanates), with allyl mustard oil (allyl isothiocyanate) being the most common. Raw wasabi contains about 0.3 g per 100 g [5]. This component is not present in its original form. When wasabi is grated and cells are broken, enzymes break down "mustard oil glycosides" to create mustard oil [5]. The fresh, sharp aroma right after grating is thought to be related to this reaction. Allyl isothiocyanate activates a sensor called TRPA1 in nerves that transmit pain and irritation, creating the sensation of heat [6]. Does wasabi really clear your nose? Eating wasabi makes it feel like your nose has opened up. However, according to reports of a conference presentation, a small 2004 study (22 people) used acoustic rhinometry to measure the volume inside the nose. The volume actually decreased significantly. It is interpreted that the feeling of clarity is due to nerve stimulation, not actual physical opening. Since this is a small-scale result from a conference abstract, it cannot be stated as a definite fact [7].
5. How do shiso, green onion, and ginger change the impression of smell?
The main component of the aroma of blue shiso (large leaf) served with sashimi is perillaldehyde [8]. The pungency and smell of alliums like green onion, onion, and garlic come from sulfur-containing precursor substances derived from amino acids [9]. The spiciness of ginger is attributed to compounds like gingerol, shogaol, and zingerone [10]. Did experiments test if these suppress fishy smells? An experiment in Japan added 11 kinds of spices to trimethylamine (TMA), a major component of raw fish odor. Onion, bay leaf, and sage showed strong suppressive effects, while ginger showed moderate effects. Gas chromatography also showed that TMA decreased over time [11]. However, this was a model experiment in a test tube and did not include wasabi, shiso, or green onion. Whether the same thing happens with actual sashimi is a different question.
6. How can you score the deliciousness of each bite in a mini experiment at home?
You can do a "mini observation" of sensory-specific satiety with things you have at home. Choose a food you are not allergic to and do this with an adult. Pick one salty snack you like. After each bite, write down the "deliciousness" on a scale of 0 to 10 in a notebook. After the fifth bite, take a bite of something with a different flavor (like a piece of apple), then go back to the original snack. Watch how the score changes. This is a record for one person and is not a scientific experiment. If the score does not change, it is not a failure; it is just a record of your tongue. It is material to think about whether the explanation that "boredom progresses linked to the food eaten" matches your own sensations.