Chapter 15 — Quiz

18 questions: 14 multiple choice, 4 short-answer. Answer key with explanations at the bottom.

Multiple Choice

1. Which of the following is the structural form of collagen as it exists in raw meat?

A. A globular protein folded around a water-soluble core B. A flat sheet stabilized by hydrogen bonds (a "beta sheet" structure) C. A triple helix of three protein strands twisted together D. A random coil with no fixed structure

2. A cook braises a brisket at 90°C (195°F) for 4 hours. What is the dominant chemical transformation responsible for the meat's tenderness?

A. The Maillard reaction throughout the meat's interior B. Caramelization of sugars in the meat C. Conversion of collagen to gelatin D. Denaturation of myoglobin

3. A freshly cut steak's interior is purple-red, but within a minute or two of being exposed to air, the color brightens to a vivid cherry red. What is happening?

A. Bacteria are multiplying on the cut surface B. Myoglobin is binding oxygen and turning to oxymyoglobin C. The meat is oxidizing and beginning to spoil D. Collagen is unwinding into gelatin

4. Which statement about the searing-seals-in-juices myth is correct?

A. Searing creates a true physical barrier that retains water in the meat. B. The seared crust is essentially watertight, preventing evaporation. C. The seared crust does not seal in juices; searing's value is the Maillard flavors and textural contrast it creates. D. Searing increases water retention by 50% or more compared to unseared meat.

5. Why does fish typically cook at lower temperatures than mammalian meat?

A. Fish has more myoglobin B. Fish collagen is less heat-stable and converts to gelatin at lower temperatures (around 50°C/122°F) C. Fish has no collagen at all D. Fish proteins denature at higher temperatures than mammal proteins

6. Which of the following pairs describes a "tough cut" likely to benefit from low-and-slow cooking?

A. Beef tenderloin and pork loin B. Beef chuck and pork shoulder C. Chicken breast and turkey breast D. Pork tenderloin and lamb loin

7. What is the approximate internal temperature for medium-rare beef?

A. 38°C (100°F) B. 54°C (129°F) C. 70°C (158°F) D. 82°C (180°F)

8. A 2 kg pork shoulder roast is removed from a 175°C (350°F) oven at internal 80°C (176°F). What approximate temperature should you expect at the center after a 25-minute rest?

A. About 70°C (158°F) — it will cool steadily B. About 80°C (176°F) — the temperature will hold C. About 85–88°C (185–190°F) — carryover will continue inward D. About 95°C (203°F) — carryover will be dramatic

9. Which of the following is the primary reason chicken thigh meat is darker (redder) than chicken breast meat?

A. The thigh contains more blood than the breast B. The thigh muscle is slow-twitch and contains more myoglobin C. The thigh is exposed to more oxygen during cooking D. The thigh contains more fat, which is darker

10. Elastin (a connective-tissue protein found in some cuts of meat) differs from collagen in that:

A. Elastin converts to gelatin even more readily than collagen B. Elastin does not break down meaningfully with normal cooking and should be trimmed C. Elastin is what gives a tender cut its tenderness D. Elastin is found only in fish, not mammals

11. Why might a cook prefer dry-brining over wet-brining a thick cut of meat?

A. Dry-brining is faster (only 10 minutes total) B. Dry-brining adds water to the meat (increasing yield) C. Dry-brining seasons the interior while drying the surface, which improves browning D. Dry-brining is required for any cut over 1 kg

12. Which technique gives a thick steak a near-uniform medium-rare interior with a hard-seared exterior?

A. Searing for 5 minutes per side over screaming high heat only B. Reverse sear (low oven first, hard sear at the end) C. Boiling, then searing D. Marinating in acid for 24 hours then grilling

13. Ground beef should be cooked to a higher internal temperature than a whole-muscle steak because:

A. Grinding makes the meat tougher B. Grinding distributes any surface bacteria throughout the meat C. Ground beef contains more collagen than steak D. Ground beef has a different myoglobin chemistry than steak

14. Wet aging beef in a vacuum bag for 21 days at refrigerator temperatures primarily produces tenderness through:

A. Mold colonies developing on the surface and breaking down proteins B. Enzymatic action (cathepsins, calpains) gradually breaking down muscle and connective-tissue proteins C. Mechanical compression from the vacuum bag D. Dehydration concentrating flavor

Short Answer

15. Explain in 3–4 sentences why a steak cooked at 49°C (rare) loses less weight during cooking than a steak from the same cut cooked at 65°C (medium-well). Tie your answer to specific protein behavior.

16. A friend tells you, "I always sear my roast first because it locks in the juices." What is the actual scientific reason that searing improves a roast, and what is the practical advice for someone who wants juicier meat?

17. Compare and contrast a 4-hour braise of beef shin at 90°C with a 36-hour sous vide cook of beef shin at 65°C. Both convert collagen to gelatin. What are some differences in the final product, and why?

18. Why is the standard recommendation for poultry doneness (74°C / 165°F) higher than the standard for beef doneness (medium-rare 54°C / 129°F)? Address both food safety and the structural difference in the meats.

Answer Key

1. C. Collagen is a triple helix — three protein strands twisted around each other and stabilized by glycine, proline, and hydroxyproline residues. This structure is what makes collagen tough at room temperature and transformable in heat.

2. C. At 90°C over 4 hours, the dominant transformation is collagen unwinding into gelatin. Maillard reactions occur on the surface during initial browning but are not the source of internal tenderness. Caramelization is a sugar reaction and not relevant here. Myoglobin denatures, but that is a color/texture detail rather than the source of tenderness.

3. B. The brightening is myoglobin (in its iron-2+ deoxygenated state, purple-red) binding atmospheric oxygen to become oxymyoglobin (cherry red). It is normal and indicates fresh, oxygen-permeable meat.

4. C. Searing does not seal in juices — the cooked, dehydrated crust is more permeable than uncooked meat, not less. Searing's actual value is Maillard reaction flavor compounds and the textural contrast of crispy crust against tender interior. (Harold McGee documented this; multiple food scientists have replicated.)

5. B. Fish collagen converts to gelatin at much lower temperatures (around 50°C / 122°F) than mammal collagen (~70°C / 158°F). This is because fish are cold-water animals; their proteins evolved to function at lower temperatures and therefore unwind at lower temperatures. This is also why fish can be served deliberately rare or "just-cooked" in ways that warm-blooded mammal meat cannot.

6. B. Beef chuck and pork shoulder are working-muscle, slow-twitch, high-collagen cuts. They benefit from low-and-slow cooking because their collagen needs time to convert. Tenderloins and loins (and chicken/turkey breast) are postural or fast-twitch, low-collagen, and best cooked hot-and-fast.

7. B. Medium-rare beef internal temperature is roughly 54°C (129°F). Below that range is rare; above is medium and beyond.

8. C. A 2 kg roast pulled at 80°C from a hot oven will continue to climb 5–8°C during a 25-minute rest. The center will likely reach 85–88°C. (This is why pulling early matters — if you waited until the thermometer read 90°C in the oven, you would push the meat well past target after rest.)

9. B. Chicken thigh is slow-twitch (sustained, low-intensity work — chickens are walkers), and slow-twitch fibers are packed with myoglobin (an oxygen-binding pigment). The myoglobin gives the meat its red color. Breast meat is fast-twitch (chickens almost never sustain flight), pale, and low in myoglobin.

10. B. Elastin is heat-stable and does not break down meaningfully during normal cooking. It is the rubbery, often yellowish material in some cuts (e.g., the silverskin or the ligamentum nuchae in the neck), and the traditional advice to trim it before cooking is, in molecular terms, advice to remove the elastin since heat will not save you from it.

11. C. Dry-brining seasons the interior (the salt eventually penetrates the meat) and dries the surface, which improves browning during cooking. Wet-brining adds water and seasons but leaves the surface wet, requiring additional drying time before high-heat cooking for proper browning. Both work; dry-brining is often preferred for cuts intended for high-heat finishing.

12. B. Reverse sear: cook at low oven temperature (around 90–120°C / 200–250°F) until just below target, then briefly sear at very high heat. The slow warming gives a near-uniform internal color (no overcooked layer just under the crust); the brief sear adds Maillard flavor and texture without overcooking.

13. B. Grinding mixes any surface bacteria throughout the meat, so the entire interior must reach a temperature high enough to kill them. A whole-muscle steak's interior is sterile (or near-so) and the surface, where any bacteria are, gets the high searing temperature; ground meat does not have this geometric advantage.

14. B. Wet aging works primarily through enzymatic action — the meat's own proteases (cathepsins and calpains) slowly break down muscle and connective-tissue proteins, increasing tenderness. Mold colonies and surface dehydration are dry-aging phenomena and don't apply to vacuum-sealed wet-aged meat.

15. Sample answer. At 49°C, only myosin (and only partially) has denatured; actin remains largely undenatured, and the muscle fibers retain most of their water-holding capacity. At 65°C, both myosin and actin have substantially denatured; actin denaturation in particular causes the muscle fibers to shrink and squeeze out water (because the unfolded actin molecules pack more tightly and have less internal water-binding). The result is a smaller, drier, gray-tan piece of meat. The percentage weight loss correlates with how far up the temperature ladder the cook has pushed the proteins.

16. Sample answer. Searing creates Maillard reaction flavor compounds on the surface — hundreds of volatile and non-volatile aromatics, plus melanoidins — and provides textural contrast (crispy crust vs. tender interior). It does not seal in juices; the cooked crust is more permeable than uncooked meat, not less. For juicier meat: don't overcook (use a thermometer), choose well-marbled cuts, brine or dry-brine ahead of time, and rest the meat after cooking so the juices that have been driven outward have a chance to redistribute and be partially reabsorbed.

17. Sample answer. Both methods convert collagen to gelatin and thus produce tender meat. Differences: - The 90°C braise drives the muscle fibers further along the temperature ladder — actin and myosin are both fully denatured, color is brown throughout, the meat has lost more water from the muscle (compensated by the gelatin and rendered fat). - The 65°C sous-vide hold is below actin's full denaturation temperature; the muscle fibers have lost much less water; the color stays pinkish; the texture is more steak-like even after collagen has converted. - Flavor: the braise has substantial Maillard development (from initial sear and from any surface above the liquid line), plus reduced cooking liquid that concentrates flavors. Sous vide produces almost no Maillard during the cook itself (a sealed bag at 65°C is too cool for it); flavor is more direct meat-protein flavor, often finished with a brief sear after. - Both are valid; the choice depends on the dish, the equipment, and the cook's taste preference.

18. Sample answer. Two reasons for the higher poultry temperature. - Food safety. Poultry is more likely to carry pathogens like Salmonella and Campylobacter than beef. The 74°C target ensures rapid pasteurization, killing these pathogens within seconds. Beef's surface bacteria are killed by searing; the interior is sterile or near-so, so the interior temperature can be lower. - Structural difference. Whole-muscle beef benefits from staying medium-rare because its texture is best at lower internal temperatures. Poultry breast actually does not benefit from going far above 65°C internally, but the safety target (74°C) is the binding constraint. (Some chefs argue for sous-vide chicken breast held longer at lower temperatures, where pasteurization is achieved by time-temperature combination — Chapter 27 will discuss the relevant pasteurization curves.) For most home cooks, 74°C is the right target for poultry.