Chapter 23 Quiz — Boiling, Simmering, Poaching, and Steaming

Fifteen multiple-choice and five short-answer questions. Answer key with explanations follows at the end.

Multiple Choice

1. At sea level, what is the highest temperature liquid water can reach in an open pot? a) 105°C b) 100°C c) 121°C d) 90°C

2. Why does a rolling boil not get hotter than 100°C even at maximum heat? a) The water has absorbed maximum energy b) Additional energy is consumed as latent heat of vaporization, converting liquid water to steam rather than raising temperature c) The pot dissipates heat too quickly d) The thermostat regulates temperature automatically

3. Pat Hammond's two-pot egg demonstration shows that: a) Boiling water at sea level varies in temperature b) Boiling and simmering are different temperatures c) Both pots are at the same temperature (100°C); the difference in egg outcomes is due to agitation, not temperature d) Eggs cook differently because of altitude

4. As elevation increases, water's boiling point: a) Stays constant at 100°C b) Rises about 1°C per 285 m of elevation c) Drops about 1°C per 285 m of elevation d) Becomes irrelevant

5. Adding a tablespoon of salt to a liter of pasta water raises the boiling point by approximately: a) 5°C — significant b) 0.15°C — negligible c) 1°C — moderate d) Salt lowers the boiling point

6. A "simmer" in cooking is best identified by: a) The temperature setting on the burner b) The visual signature: bubbles rising lazily from the edges, surface trembling, no rolling c) A specific time (after 10 minutes) d) Bubbles all over the surface

7. Why is a stockpot at a rolling boil cloudy and greasy compared to a simmered one? a) The bones are different b) Boiling agitates fat into a permanent emulsion and pulverizes coagulated proteins back into the broth c) Boiling extracts more flavor d) Boiling chemically transforms the fat

8. The conversion of collagen to gelatin in stock-making is best described as: a) A protein hydrolysis that runs above 60°C, with rate accelerating up to about 90°C b) A sudden phase change at 80°C c) A reaction that requires acid d) A reaction that happens only in pressure cookers

9. Why does steamed broccoli retain more vitamin C than boiled broccoli? a) Steam contains vitamin C b) Vitamin C is fat-soluble c) Water-soluble vitamins leach into boiling water and are discarded; in steaming, the food never sits in a water bath, so leaching is minimal d) Steaming kills less of the vitamin

10. Steam at sea level is at what temperature? a) 110°C b) 100°C c) 90°C d) 130°C

11. Japanese dashi differs fundamentally from French stock in that: a) Dashi takes longer to cook b) Dashi uses cold or warm extraction (kombu) and a brief 60-second steep (bonito), with no animal collagen — relying on free glutamate plus inosinate for umami synergy rather than gelatin for body c) Dashi requires meat d) Dashi is boiled vigorously

12. Salt in pasta water primarily: a) Raises the boiling point significantly b) Flavors the pasta as it hydrates and slightly affects surface texture; does not meaningfully change cooking temperature c) Prevents sticking d) Speeds the chemistry of starch gelatinization

13. A poached egg ideally cooks at: a) 100°C boiling water b) 70-85°C — visible steam, no real bubbles c) 60°C — too cool d) 110°C — pressurized

14. Why is the water at a frémissement (the "shivering surface" simmer) the empirical sweet spot for stock-making? a) Because it is exactly 100°C b) Because at ~85°C, collagen-to-gelatin conversion is fast enough to be efficient, but not so hot that the gelatin further degrades into smaller, less-functional fragments; agitation is gentle enough not to emulsify fat c) Because traditional French chefs preferred it d) Because it requires the least energy

15. What is one reason the Japanese cook Heinz Kawano said, "We do not boil dashi. To boil it is to spoil it"? a) Boiling makes the dashi look ugly b) The agitation of boiling extracts bitter compounds from kombu and bonito, and high heat denatures the umami-bearing proteins; the optimal extraction is gentle and brief c) Boiling is more expensive d) Tradition forbids it

Short Answer

16. Explain why a covered pot reaches boiling faster than an uncovered pot. Use the words "evaporation" and "latent heat" in your answer. (3-4 sentences.)

17. A friend in Mexico City complains that her hard-boiled eggs are always slightly underdone. What's happening, and what should she do? (Mexico City elevation: ~2,240 m.) (2-3 sentences.)

18. Distinguish in chemical terms why a roasted (dry-heat) sweet potato develops brown crust and caramelized flavors, while a boiled sweet potato never browns. (3-5 sentences.)

19. Pasta water is sometimes saved as "an ingredient" for finishing pasta sauces. What is the chemistry that makes this useful, and why is the salty starchy water from cooked pasta different from plain salted water? (3-5 sentences.)

20. A reader at sea level wants to make beef stew. Their recipe says "simmer for 3 hours." Why does this take so long, and what is happening to the meat at this temperature window? Identify the relevant chemistry. (4-6 sentences.)

Answer Key

1. b — At sea level, water boils at 100°C / 212°F. Liquid water in an open pot cannot exceed this temperature; any additional energy converts liquid to vapor (phase change) rather than raising temperature.

2. b — Once water reaches its boiling point, additional heat input is consumed as latent heat of vaporization — about 540 calories per gram of water converted to steam. This is roughly 7× more energy than was required to heat that gram from 20°C to 100°C. The temperature stays pinned at the boiling point until all the water has evaporated.

3. c — Both pots in Pat's demonstration are at the same temperature (100°C is the boiling point regardless of how vigorous the boil is). The difference in egg outcomes is due to physical agitation — violent bubbles bruise and crack the egg, while a gentle simmer treats it kindly. This is the "boil vs. simmer" lesson in its purest form.

4. c — Atmospheric pressure decreases with elevation, and water's boiling point decreases proportionally. The rule of thumb is about 1°C per 285 m of elevation.

5. b — Boiling-point elevation by salt is real but extremely small. Roughly 0.15°C for typical pasta-water salinity. This is not a meaningful cooking effect. Salt is doing other things (flavoring the pasta, slightly affecting surface texture), but raising temperature is not one.

6. b — A simmer is identified by visual signature: lazy bubbles drifting up from the edges, surface trembling, no rolling. This corresponds to a temperature of 85-95°C, regardless of what your burner dial says.

7. b — Vigorous boiling has two destructive effects on stock: it agitates fat into a permanent suspension (cloudiness, greasiness) and pulverizes the proteins that would otherwise rise as scum to be skimmed. Simmered stock is clear and clean because neither effect happens at gentler agitation.

8. a — Collagen-to-gelatin conversion is a protein hydrolysis (water molecules inserting into the collagen triple helix and unwinding it). Below 60°C the rate is essentially zero; above 60°C it accelerates exponentially with temperature. Above ~90°C sustained, gelatin starts to further hydrolyze into smaller, less-functional fragments. The empirical sweet spot is about 85°C.

9. c — Boiled vegetables sit in a water bath that water-soluble vitamins (and pigments, and minerals) leach into; that water is then discarded, taking 30-50% of the vitamin C with it. Steamed vegetables don't sit in water — leached compounds drip down to the steaming water below the food, but most of the leaching that boiling causes simply doesn't happen because the food isn't in contact with bulk water.

10. b — Steam at sea level is at 100°C, the same temperature as boiling water. The energy advantage of steam is the latent heat of vaporization (~540 calories per gram) released when steam condenses on cold food.

11. b — French stock builds body from animal collagen converted to gelatin over hours of simmering. Dashi extracts free glutamate from kombu (cold or warm) and inosinate from bonito (60-second steep), giving umami synergy without animal collagen. The two traditions arrived at completely different chemistries for the same goal of "savory broth."

12. b — Salt's main contribution to pasta water is flavoring the pasta as it hydrates from the inside. The boiling-point elevation is negligible (0.15°C). Salt does also slightly affect surface texture and the structure of the gluten-starch matrix, but not in a way that changes cooking time.

13. b — Eggs poach optimally at 70-85°C, where the water is steaming but not bubbling. The egg whites set at ~62-65°C; the yolks begin to thicken at ~70°C. A 100°C bath is too violent and produces ragged whites; a 60°C bath is too cool to set the white properly.

14. b — At 85°C, the kinetics of collagen-to-gelatin conversion are favorable: fast enough for efficient extraction, but not so hot that the gelatin further degrades into less-functional fragments. The agitation at this temperature is gentle (lazy bubbles at the edges, surface trembling), which keeps fat from emulsifying and proteins from being pulverized into the broth.

15. b — The chemistry of dashi extraction is gentle: cold/warm steeping for kombu, brief steep for bonito. Boiling extracts bitter compounds (some hop-like compounds in kombu, and bitter peptides from over-extraction of bonito), and the agitation interferes with the delicate flavor balance. Dashi is one of the cleanest examples in cooking of why "more heat" is not always "more chemistry."

Short Answer Sample Responses

16. When water heats in an open pot, surface evaporation is constantly carrying away energy as latent heat — each evaporated molecule takes about 540 calories per gram with it. The burner's energy input is partly going into making steam (which leaves) rather than raising the water's temperature, so heating is slow. Covering the pot creates a closed atmosphere; vapor accumulates above the water until it reaches saturation, at which point evaporation effectively stops (molecules leaving and condensing back into the liquid balance out). With evaporation halted, all the burner's energy goes into raising the water's temperature, and the pot reaches boiling significantly faster.

17. At Mexico City's elevation (~2,240 m), water boils at about 92°C / 198°F instead of 100°C / 212°F at sea level. Egg yolks need to reach 70-75°C to set firmly, which requires more cooking time at the lower water temperature. She should simmer her eggs about 2-3 minutes longer than a sea-level recipe suggests, or use a pressure cooker to push past the altitude penalty.

18. Boiling water tops out at 100°C, which is far below the activation temperature for the Maillard reaction (~140°C) and for caramelization (~160°C). A boiled sweet potato never browns because the surface temperature can't exceed 100°C as long as there is liquid water present. A roasted sweet potato, surrounded by hot dry air at 200°C+, has its surface water evaporate and the surface temperature climb above 100°C, into the range where Maillard and caramelization both run. The brown crust is melanoidins from Maillard plus caramels from sugar breakdown — chemistry that is geometrically impossible in liquid water below 100°C.

19. Cooked pasta releases starch into its cooking water through gelatinization (Chapter 9) — surface starch granules absorb water, swell, and burst, releasing dissolved starch molecules into the water. The resulting starchy water acts as both a viscosity agent (raising the bulk viscosity of any sauce it's added to) and an emulsifying agent (the dissolved starch molecules can stabilize oil-in-water mixtures, holding fat and water together). This is why a small amount of pasta water added to a pan of olive oil and cheese transforms a thin oily mixture into a glossy clinging sauce. Plain salted water has no starch and cannot perform either function. The salt content is a separate matter (flavoring); the starch content is what makes pasta water "an ingredient."

20. The 3-hour simmer is required because beef stew typically uses tough cuts (chuck, brisket, shank) that are full of collagen — a fibrous structural protein in the connective tissue. Below 60°C, collagen is rubbery and chewy; it requires hours at 60-90°C to hydrolyze into gelatin, which is soft and water-soluble. The empirical sweet spot is around 85°C, where the conversion rate is favorable and the gelatin doesn't further degrade. At a vigorous boil (100°C), the muscle fibers shrink violently and squeeze out moisture, making the meat tough and dry; at a simmer, the muscle proteins relax and the collagen melts, producing tender meat. The 3-hour duration reflects the relatively slow first-order kinetics of collagen hydrolysis at this temperature — a roughly 2-3× rate increase per 10°C, but starting from a slow base.