Quiz — Chapter 6: Taste, Flavor, and Aroma

18 questions. 14 multiple choice, 4 short answer. Mix of recall, application, and "explain why" questions. Answer key with explanations at the bottom.

Multiple Choice

1. Approximately what percentage of "flavor" is actually smell, traveling from the food in your mouth up the nasopharynx to the olfactory bulb? - a) 20% - b) 50% - c) 80% - d) 95%

2. The five generally-accepted basic tastes are: - a) Sweet, sour, salty, bitter, hot - b) Sweet, sour, salty, bitter, fat - c) Sweet, sour, salty, bitter, umami - d) Sweet, sour, salty, bitter, astringent

3. Which of the following is the correct status of the "tongue map" (sweet at the tip, bitter at the back, etc.)? - a) Verified by modern research and still taught in textbooks because of accuracy. - b) An oversimplification of older research; all tastes are perceived everywhere on the tongue. - c) True for adults but not for children. - d) True only for the four "primary" tastes; umami is detected uniformly.

4. Umami was scientifically identified by which researcher, in what year? - a) Louis Pasteur, 1864 - b) Kikunae Ikeda, 1908 - c) Linda Bartoshuk, 1991 - d) Charles Zuker, 2002

5. The dominant umami molecule in foods is: - a) Sodium chloride - b) Glutamate - c) Capsaicin - d) Citric acid

6. Which of the following is a true statement about MSG? - a) MSG is harmful to most people and should be avoided. - b) MSG is the same molecule as the glutamate in parmesan cheese, soy sauce, and tomatoes. - c) MSG was found to cause "Chinese Restaurant Syndrome" in controlled trials. - d) MSG is banned in most countries.

7. Retronasal olfaction refers to: - a) Smelling food before you put it in your mouth. - b) Volatile compounds reaching your olfactory bulb from the back of your throat while chewing. - c) The sense of smell during a head cold. - d) Smell that produces taste.

8. Capsaicin (the active compound in chiles) produces a sensation of heat by: - a) Activating the umami receptor. - b) Raising the actual temperature of the food. - c) Activating the TRPV1 receptor, which is normally activated by painful heat (above 43°C). - d) Stimulating bitter receptors.

9. Chemesthesis includes: - a) Capsaicin heat, mint cool, and carbonation tingle. - b) Sweet, sour, salty, bitter, and umami. - c) Aroma compounds traveling through the nose. - d) Color and visual cues from food.

10. Approximately how many distinct olfactory receptor types do humans have? - a) About 5 - b) About 50 - c) About 400 - d) About 4,000

11. Why does food taste blander during a head cold? - a) The taste buds on the tongue are inflamed. - b) The salt and sugar in food can't dissolve in the saliva. - c) The mucus in the inflamed nasal passages prevents volatile compounds from reaching the olfactory epithelium. - d) The tongue's nerve signals to the brain are interrupted.

12. Glutamate combined with IMP (a nucleotide in meat) or GMP (a nucleotide in mushrooms) produces what kind of effect on perceived umami? - a) Suppression — the combination tastes less savory than glutamate alone. - b) Synergy — the combination tastes much more savory than glutamate alone. - c) No effect — IMP and GMP don't change perceived umami. - d) Bitter shift — the combination tastes bitter rather than savory.

13. A "supertaster" is someone who: - a) Has a higher density of fungiform papillae and a more sensitive bitter receptor variant. - b) Has been trained as a chef. - c) Lacks the bitter receptor. - d) Has more than five basic tastes.

14. Which of the following pairings is supported by the food-pairing hypothesis (shared volatile compounds)? - a) Strawberry and balsamic vinegar. - b) Lemon and butter. - c) Salt and pepper. - d) Bread and butter.

Short Answer

15. Explain in your own words why pinching your nose while eating a strawberry causes the strawberry to "lose its flavor." What is happening physiologically? When you release your nose, what happens?

16. The 1968 NEJM letter on "Chinese Restaurant Syndrome" had real consequences for Chinese-American restaurants and for the public perception of MSG. What does the modern scientific consensus on MSG actually say? Why might it have been so hard to dispel the original concern?

17. A friend says, "I don't like spicy food because the heat overwhelms my taste buds." What is technically wrong with this statement? What is actually happening when someone perceives spiciness?

18. A home cook is making chicken soup. The base broth tastes "thin and watery." Working from this chapter, list three concrete strategies — drawing on the chemistry of taste and aroma — that the cook could try, and explain the rationale for each.

Answer Key

1. (c) 80%. This is the rough rule of thumb. The remaining 20 percent is the contribution of taste (sweet, sour, salty, bitter, umami), texture, temperature, and visual cues combined. The exact number is not precise — different studies estimate the smell contribution at 70-90 percent depending on methodology — but 80 percent is the commonly-cited figure.

2. (c) Sweet, sour, salty, bitter, umami. Hot is a chemesthetic sensation, not a taste. Astringency is also chemesthetic. Fat is a candidate sixth taste under active research but not yet universally accepted as a fifth.

3. (b) An oversimplification of older research. The original 1901 paper found minor regional sensitivity differences, but the cartoon "tongue map" with exclusive regions for each taste was a popularization that turned into textbook canon despite being inaccurate. All regions of the tongue can detect all five tastes, with at most very small regional sensitivity variations.

4. (b) Kikunae Ikeda, 1908. Ikeda was studying kombu dashi, identified glutamate as the active compound, named the new taste umami, and patented MSG production. He founded Ajinomoto, which still exists today.

5. (b) Glutamate. Specifically, free glutamate ions (the amino acid in its dissociated form). Foods rich in free glutamate include parmesan, tomatoes, mushrooms, miso, soy sauce, anchovies, kombu, and aged or slow-cooked meats.

6. (b) MSG is the same molecule as the glutamate in parmesan cheese. The chemistry is identical; the source (industrial fermentation vs. cheese aging vs. tomato cooking) does not change the molecule. Decades of controlled trials have failed to confirm any reproducible "Chinese Restaurant Syndrome" effect, and major food-safety bodies classify MSG as generally safe.

7. (b) Volatile compounds reaching the olfactory bulb from the back of your throat while chewing. This is the dominant route by which aroma reaches your nose during eating. Orthonasal olfaction (sniffing) is a separate route.

8. (c) Activating the TRPV1 receptor. TRPV1 is normally activated by painful heat (above 43°C / 109°F). Capsaicin binds it and triggers it as if the tongue were actually burning, producing the sensation of heat without temperature change. Other chemesthetic compounds (menthol, mustard oil) hijack other temperature/pain receptors similarly.

9. (a) Capsaicin heat, mint cool, and carbonation tingle. All three are chemesthetic — they activate temperature/pain pathways rather than dedicated taste receptors. They are real and important sensations but not "tastes" in the formal sense.

10. (c) About 400. Humans have roughly 400 functional olfactory receptor types. Each one responds to multiple molecules; each molecule activates multiple receptors. The combinatorial coding lets us distinguish thousands of distinct odors.

11. (c) Mucus in the nasal passages prevents volatiles from reaching the olfactory epithelium. Your taste buds are still functional during a cold; sweet still tastes sweet, salt still tastes salty. What's lost is the aromatic component, which is most of "flavor." The receptors are fine; the airflow is impaired.

12. (b) Synergy. Glutamate plus IMP, or glutamate plus GMP, can taste up to 5-10 times more savory than the same total concentration of glutamate alone. This is why dashi (kombu = glutamate, bonito = IMP) tastes so much more savory than either ingredient alone, and why cooking traditions worldwide combine ingredients across umami families (tomato + parmesan, chicken + mushrooms, etc.).

13. (a) Higher density of fungiform papillae and more sensitive bitter receptor. About 25 percent of the population are supertasters, with a particular variant of the TAS2R38 gene. They tend to perceive bitter foods as more intense and may avoid coffee, brussels sprouts, and dark chocolate without conditioning.

14. (a) Strawberry and balsamic vinegar. Both contain ethyl butyrate, ethyl hexanoate, and similar fruity ester compounds. The other pairings work for various reasons but do not rely on shared volatile compounds in the same way.

15. Sample answer: Pinching the nose blocks the retronasal olfactory pathway — volatile aromatic compounds released by the chewed strawberry can no longer travel up the nasopharynx to the olfactory bulb at the front of the brain. The taste receptors on the tongue still function, so you still perceive sweet, sour, etc., but the 80 percent of "flavor" that comes from aroma is offline. The strawberry tastes generic — sweet, slightly tart, watery, fibrous — without its identifying volatile signature. Releasing the nose suddenly opens the pathway; accumulated volatiles flood through and the olfactory bulb receives the strawberry's aromatic profile, which the brain instantly recognizes as strawberry.

16. Sample answer: The modern scientific consensus is that MSG is generally safe, that the "Chinese Restaurant Syndrome" symptoms have not been replicable in controlled trials, and that the original 1968 letter was speculative and lacked scientific support. Why was it hard to dispel? Several reasons: the NEJM lent the claim institutional authority; the framing was racially specific (singling out Chinese cuisine while ignoring equally-MSG-rich Italian, French, Japanese, etc., cooking) and tapped into pre-existing biases about Asian food; the nocebo effect produced real symptoms in people who expected to react; and the food industry had a financial interest in the panic (companies advertising "no MSG" benefited from the perception even if it was false). The combination of bad science, racial bias, and industry incentive produced a self-sustaining myth that took 50+ years to formally retract.

17. Sample answer: "Spicy food" produces sensations through the chemesthetic pathway, not the taste pathway. Capsaicin in chiles activates TRPV1, a receptor that is normally activated by painful heat. The sensation is real (it is a true firing of pain/temperature receptors) but it is not a "taste" — taste buds are not involved. The friend's statement implies that taste buds are being "overwhelmed" by spice, but the taste buds are processing taste signals (sweet, sour, etc.) normally; the chemesthetic system is processing a separate (and intense) signal in parallel. The friend may simply prefer not to activate this pain/temperature pathway, which is a perception preference rather than a taste limitation.

18. Sample answer: Three strategies, with rationale: 1. Add umami sources — soy sauce, tomato paste, parmesan rind, dried mushrooms, fish sauce. Each adds free glutamate (and some add synergistic IMP or GMP), increasing the perceived savoriness without adding salt. The thinness is often a result of insufficient umami load. 2. Add aromatic compounds — toast and grind whole spices, bloom them in fat, add fresh herbs at the end, finish with citrus zest. The "thin" perception may be partly an aromatic deficiency; adding volatile complexity makes the broth taste fuller. 3. Adjust salt and acid in tandem — taste, then add a pinch of salt (which sharpens umami perception), and a few drops of lemon juice or vinegar (which sharpens the salt perception). The cross-modulation effects cumulate. Often a thin broth is missing one of these three legs (umami, aroma, salt-acid balance) rather than just water content.