Chapter 27 Quiz — Sous Vide

Multiple Choice (Questions 1–15)

1. The French phrase sous vide literally translates as: - a) Slow cooking - b) Under vacuum - c) Below boiling - d) Sealed in glass

2. Which two cooks are usually credited with developing modern sous vide cooking in France in the 1970s? - a) Auguste Escoffier and Marie-Antoine Carême - b) Bruno Goussault and Georges Pralus - c) Paul Bocuse and Alain Ducasse - d) Ferran Adrià and Heston Blumenthal

3. The principal advantage of cooking in a precision water bath versus a hot pan is: - a) Water cooks food faster than oil - b) Water carries flavor better than air - c) The food cannot exceed the bath temperature, eliminating overshooting - d) Sous vide produces a deeper Maillard crust than a pan

4. At sea level, the water in a sous vide bath cannot exceed: - a) 50°C / 122°F - b) 80°C / 176°F - c) 100°C / 212°F - d) 200°C / 392°F

5. The standard sous vide temperature for medium-rare steak is approximately: - a) 45°C / 113°F - b) 54°C / 129°F - c) 65°C / 149°F - d) 75°C / 167°F

6. Why does a 63°C / 145°F egg held for 45 minutes have a custard-thick yolk and a partially-set white? - a) The yolk and the white are the same protein - b) Different proteins in the egg denature at different temperatures, and 63°C is between the thresholds for some white proteins (denatured) and others (not denatured) - c) The bath has cooked the yolk faster than the white - d) The egg shell insulates the white but not the yolk

7. A 12-log reduction of Salmonella means the bacterial population is reduced by a factor of: - a) 12 - b) 1,000 - c) 1,000,000 - d) 1,000,000,000,000 (one trillion)

8. The D-value of a bacterium at a given temperature describes: - a) The temperature at which the bacterium is killed - b) The time required at that temperature to reduce the population by 90% (one log) - c) The total number of bacteria present - d) The depth of penetration of heat

9. Which is true about pasteurization in sous vide cooking? - a) It only works at 73°C / 165°F or higher - b) Lower temperatures held longer can produce equivalent safety reductions (e.g., 60°C for 30 minutes ≈ 73°C instantaneously) - c) Sous vide does not require pasteurization considerations - d) Pasteurization is impossible below 100°C

10. The standard practice after a sous vide cook is to: - a) Serve immediately straight from the bag - b) Sear the surface in a hot pan, on a torch, or on a grill to develop Maillard flavor and color - c) Refrigerate before eating - d) Boil briefly to finalize cooking

11. A 2-inch (5 cm) steak takes approximately how much longer to reach bath temperature than a 1-inch (2.5 cm) steak of the same cut? - a) The same time - b) Twice as long - c) Four times as long - d) Eight times as long

12. Which of the following is NOT a typical limitation of sous vide cooking? - a) Maillard browning does not occur in the bag - b) Wood-smoke flavor is not produced - c) Food cannot be cooked to a specific target temperature - d) Cooking takes longer than equivalent pan or oven preparations

13. The "water displacement method" for sealing a freezer bag of food is: - a) Filling the bag with water before sealing - b) Lowering the open bag slowly into the water bath; water pressure pushes air out - c) Boiling the bag to remove air - d) Sealing the bag in a vacuum oven

14. A typical home immersion circulator holds the bath temperature within: - a) ±10°C - b) ±5°C - c) ±0.5°C or better - d) The temperature drifts uncontrollably

15. A 24-hour sous vide cook at 71°C / 160°F on a chuck roast produces: - a) The texture of a hard braise (collagen broken down, fibers dry) - b) The texture of a tartare (raw) - c) Both the gelatinous quality of a braise (collagen → gelatin) and the firm texture of a steak (because the muscle proteins are not driven past 71°C) - d) An indistinguishable result from a 1-hour cook

Short Answer (Questions 16–20)

16. Explain why a sous vide steak cannot overcook. Use the words "temperature gradient," "bath temperature," and "denaturation."

17. A home cook wants to serve a chicken breast that is fully pasteurized but still juicy. The conventional method (cooking to 73°C internal) tends to dry out the breast. Describe the sous vide approach (specific temperature, time, and the underlying pasteurization-curve reasoning) that solves this problem.

18. Sous vide cannot produce the Maillard reaction in the bag. Why not? And what is the standard solution?

19. The 63°C / 145°F egg has a texture that no other cooking method can produce. Explain why, referencing the different denaturation temperatures of egg-white and egg-yolk proteins.

20. Speculate on why a long sous vide cook at moderate temperature (e.g., 71°C for 24 hours) produces a tougher cut's "best" texture. What is happening to the collagen versus what is happening to the muscle fibers, and why does this combination of effects benefit from time alone?

Answer Key

1. b) Under vacuum.

2. b) Bruno Goussault and Georges Pralus. Goussault came from industrial food science (working with Cryovac on institutional reheating); Pralus was a chef at Restaurant Troisgros experimenting with foie gras.

3. c) The food cannot exceed the bath temperature. This eliminates the overshoot problem that defines pan and oven cooking.

4. c) 100°C / 212°F. The sous vide bath is bounded by water's boiling point at sea level. (At higher elevations the boiling point is lower.) For most sous vide cooks, the bath temperature is far below 100°C.

5. b) 54°C / 129°F. Within a few degrees, this is the standard "medium-rare from edge to edge" target.

6. b) Different proteins denature at different temperatures. Ovotransferrin (a white protein) denatures around 60–63°C; ovalbumin (the major white protein) doesn't fully denature until ~84°C. Yolk proteins thicken around 62–70°C. At 63°C held long enough, the yolk thickens, ovotransferrin denatures (some white sets), but ovalbumin does not — yielding the unique partial-set texture.

7. d) One trillion (10^12). A "log" is a factor of 10, so 12 logs is 10^12.

8. b) The time required at a given temperature to reduce the bacterial population by 90% (one log).

9. b) Lower temperatures held longer produce equivalent safety reductions. This is the foundation of low-temperature pasteurization in sous vide.

10. b) Sear the surface in a hot pan, on a torch, or on a grill. The interior is already cooked; the sear adds the Maillard reaction (Chapter 8) for color and flavor.

11. c) Four times as long. Heat penetrates a slab on the order of L²/α, where L is thickness — so doubling the thickness quadruples the time.

12. c) Sous vide can cook food to a specific target temperature; that is its central advantage. The other three (no Maillard, no wood smoke, longer total cook time) are real limitations.

13. b) Lowering the open bag slowly into the water; the water pressure pushes air out through the open end, which is then sealed before water enters.

14. c) ±0.5°C or better. Modern home immersion circulators are highly accurate. Industrial units can hold ±0.1°C.

15. c) Both gelatinous and firm. The collagen has had 24 hours to convert to gelatin (which it does slowly even at 71°C); the muscle proteins denatured early but never went past 71°C, so they retain water and structure better than they would in a hard braise.

16. Sample answer: In a hot pan, the steak develops a temperature gradient — the surface is at the pan's temperature (200°C+), the center is much cooler. The cook's job is to pull the steak when the center hits the target (e.g., 54°C) before the outer layers overcook. In sous vide, the bath temperature is the target temperature. The steak rises asymptotically to the bath temperature and stops; nowhere in the steak can ever exceed the bath temperature. So denaturation cannot proceed past the target temperature — the steak cannot overcook because there is no driving force for additional heating once equilibrium is reached.

17. Sample answer: Pasteurization of Salmonella depends on time and temperature, not just temperature. A 12-log reduction can be achieved at 60°C / 140°F in approximately 30 minutes — equivalent safety to "instantaneous" pasteurization at 73°C. So a home cook can cook chicken breast at 60°C in a sous vide bath for 90 minutes (1 hour come-up time + 30 minutes pasteurization, conservatively). At 60°C, myosin in the muscle has denatured (so the chicken is firm and opaque) but actin has not (which would otherwise contract sharply and squeeze out water). The result is fully pasteurized chicken that retains its juice — dramatically different in texture from breast cooked to 73°C internal.

18. Sample answer: The Maillard reaction (Chapter 8) needs temperatures around 140°C / 285°F or higher to run at meaningful speed. The water in a sous vide bath caps at 100°C at sea level, and most sous vide cooks are well below that. The standard solution is the post-cook sear: dry the surface of the food and apply intense, brief heat (cast iron at 230°C+, a torch, a hot grill) for 30–60 seconds per side. This develops the brown crust without further cooking the interior.

19. Sample answer: Egg whites and egg yolks contain different proteins with different denaturation temperatures. Ovotransferrin (a white protein) denatures around 60–63°C. Ovalbumin (the dominant white protein) doesn't fully denature until around 84°C. Yolk proteins begin thickening around 62°C and continue to set up to about 70°C. At 63°C held for 45 minutes, the yolk thickens to a custard consistency, ovotransferrin in the white denatures, but ovalbumin does not fully denature — so the white is partially set (opaque, tender) rather than firm. No conventional cooking method (boiling, poaching) can hold the egg precisely at this in-between temperature long enough to achieve this texture.

20. Sample answer: Tough cuts like chuck contain large amounts of collagen (connective tissue), which is chewy when raw or briefly cooked. Collagen converts to gelatin (smooth, savory, dissolved in liquid) by hydrolysis — a chemical reaction that takes time at moderate temperatures (e.g., several hours at 70°C, accelerating at higher temperatures). Meanwhile, the muscle proteins (myosin, actin) denature quickly at any cooking temperature above ~55°C, and at higher temperatures they contract sharply and squeeze out water, producing the dry, stringy texture of an over-braised cut. A long cook at 71°C splits the difference: collagen has time to convert to gelatin (24 hours is enough); but the muscle has plateaued at 71°C, where actin has begun to denature but the contraction is moderate and the water loss is modest. The result is the rare combination of fully tender connective tissue and still-juicy muscle — a texture no other cooking method (which couples high temperature with shorter cook time) can produce.