Chapter 14 Exercises — Eggs

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Chapter 14 Exercises — Eggs

⚠️ Allergen frame for this entire file. Eggs are one of the top-8 allergens. Every Kitchen Lab below carries an explicit allergen flag and a vegan substitution where one is feasible. The substitutions are not consolation prizes — they are different chemistries that succeed for different reasons. Where a substitute cannot reproduce a specific egg behavior, we say so.

Kitchen Lab 1 — Five Eggs, Five Temperatures (the visual coagulation chart)

This is Pat's signature classroom demo and the single most reliable egg-chemistry lesson in the chapter. You will see, in real time, the protein-denaturation chart from the body of the chapter become physical objects on a plate.

Materials

5 large eggs (refrigerator-cold)
A pot deep enough to hold all five eggs fully submerged (at least 10 cm / 4 inches of water)
An instant-read thermometer (a sous-vide circulator if you have one)
A slotted spoon
A small bowl of ice water
5 small plates or wide ramekins for plating
Optional: 5 clean glass canning jars (one per egg) if you want the "egg cracked into a jar" version
Salt, pepper, and bread for tasting

Time

About 75 minutes total: 15 minutes of setup, 45–60 minutes of cooking, 5 minutes of plating and tasting. The eggs cook simultaneously, not in sequence.

Allergen flags

⚠️ Eggs (top-8). No vegan version of this specific lab — its purpose is to map egg coagulation. A parallel lab for vegan readers: aquafaba whip-test (Lab 3 below).

Procedure (in-shell version)

Set up your water bath. If you have a sous-vide circulator, this is straightforward — set the bath to your target temperature and wait for it to stabilize. Without a circulator, fill a deep pot, heat the water to about 5°C above your target, then turn the heat off and let it drift down to target. You will need to manage temperature with brief low-heat pulses.
You are aiming to hold eggs at five different bath temperatures: 60°C (140°F), 65°C (149°F), 70°C (158°F), 80°C (176°F), and 90°C (194°F). You can do this in five sequential rounds with one pot, or in parallel if you have multiple pots.
For each temperature, lower a refrigerator-cold egg gently into the water with a slotted spoon. Hold for 45 minutes (essential for the in-shell version, because heat penetrates slowly through the shell and the white).
Remove each egg, transfer briefly to ice water (just enough to make peeling possible), peel carefully, and plate.
Label each plate with its temperature.

Procedure (cracked-into-jar version — Pat's classroom variant)

Crack each egg into a clean wide-mouth canning jar. Cap loosely (not airtight).
Submerge each jar in a water bath at one of the five target temperatures, with the water level reaching above the egg level inside the jar.
Hold for 30 minutes (faster than in-shell because there is no shell to slow heat transfer).
Lift each jar out, slide the egg onto a plate, and label.

Expected results

60°C (140°F): Egg looks essentially raw. White is slightly cloudy on the edges (ovotransferrin has begun to set) but the bulk is still liquid. Yolk is unchanged.
65°C (149°F): White is soft-set, tender, slightly translucent. Yolk is creamy, almost pourable, looks more set than raw but flows. This is Maya's grandmother's egg.
70°C (158°F): White is fully set, tender. Yolk is firm-creamy — the texture of a smooth custard.
80°C (176°F): White is firm and slightly weeping water (small clear droplets on the surface). Yolk is fully firm, dry, slightly crumbly.
90°C (194°F): White is rubbery, distinctly weepy. Yolk has a faint gray-green ring around its outer surface (iron sulfide). The whole egg is overcooked.

Discussion during plating

Have each taster put a small piece from each egg in their mouth in temperature order. Ask them to describe the texture differences in their own words before you give them the protein chart. Most people, with no prior food-science background, can identify a clear progression. They are tasting a chart.

Troubleshooting

All my eggs look the same. Your water bath drifted. The temperature differences in this lab are 5–10°C apart; if your bath wandered by 10°C, the differences blur. Use a thermometer or circulator.
My 65°C egg has firmer-than-creamy yolk. Either the bath ran above 65°C, or the eggs were too small (smaller eggs hit equilibrium faster). Try with large eggs and verify temperature.
My 70°C egg has runny yolk. Bath ran below 70°C. Or the hold time was too short.
The 90°C egg's gray ring is huge. That ring is iron-sulfur (iron from the yolk meeting hydrogen sulfide from the white at high heat). The longer the cook above 80°C, the more pronounced. Reduce time next round.

Classroom adaptation

Pat runs this with a laboratory hot plate and a 1-L beaker, with a thermometer clamped to the side. She does it as a Friday demo — students predict textures from the protein chart in their notebook before she pulls the eggs. Most predictions are accurate to within one texture grade. The lab also doubles as a chemistry-lab safety lesson (hot water, raw egg handling, heat shielding).

Kitchen Lab 2 — Mayonnaise from One Yolk (oil-in-water emulsion)

A direct experience of how the yolk's lecithin holds oil in suspension. You will produce, in about 10 minutes, an emulsion with about 4 to 1 oil-to-water ratio that holds together for a week in the refrigerator.

Materials

1 large egg yolk (room temperature — see note)
1 teaspoon (5 mL) Dijon mustard (optional but stabilizing)
1 tablespoon (15 mL) lemon juice or white wine vinegar
¾ to 1 cup (180–240 mL) neutral oil (vegetable, sunflower, light olive — not extra-virgin, which goes bitter when whipped)
¼ teaspoon fine salt
A medium bowl with a damp towel beneath it (to keep it from sliding)
A whisk or a small electric hand mixer

Time

10–15 minutes active. The mayo is ready immediately.

Allergen flags

⚠️ Eggs (top-8). Mustard (in some classifications, an allergen as well). Vegan substitution: see Aquafaba Mayonnaise note below — the emulsion still works, with chickpea liquid replacing the yolk's emulsifier role.

Procedure

Bring the yolk to room temperature. A cold yolk can shock the oil and break the emulsion. (Run the egg under warm tap water for a minute if you forgot to set it out.)
Separate the yolk from the white (save the white for a meringue or scrambled eggs). Place the yolk in your bowl.
Whisk in the mustard and salt. Whisk for 30 seconds — you are pre-mixing the emulsifiers.
Whisk in the lemon juice or vinegar.
Now begin adding the oil. First, add it drop by drop, whisking continuously, for the first 2 to 3 tablespoons (30–45 mL). Each drop must be incorporated before the next is added. The mixture will become noticeably thicker after about a tablespoon of oil — the emulsion has formed.
Once the emulsion is established, increase the oil flow to a thin steady stream while whisking. Keep going until you have added about ¾ cup (180 mL) total. The mayonnaise will be thick, glossy, and pale yellow.
Taste. Adjust salt, lemon, mustard. If too thick, whisk in a teaspoon of water to thin.
Refrigerate. Use within a week.

Vegan substitution: Aquafaba mayonnaise

Replace the yolk with 3 tablespoons (45 mL) of aquafaba (the liquid from a can of chickpeas, drained and reserved). The chickpea liquid contains saponins and small proteins that act as emulsifiers — different molecular cast than yolk lecithin, but the same job. Whisk the aquafaba with mustard, salt, and lemon juice for 60 seconds before starting the oil drizzle. Proceed exactly as above. The result is slightly less rich than yolk-mayo (because there's no yolk fat) but is a real, stable emulsion. Will keep about 4 days refrigerated.

Expected results

A pale yellow (egg) or off-white (aquafaba) glossy thick spread. It holds a peak briefly when you lift the whisk. It can be flavored further (smashed garlic for aïoli, chipotle for spicy mayo, herbs and lemon zest for tartar sauce).

Troubleshooting

The mayonnaise is liquid; oil is pooling. The emulsion broke. Most common cause: oil added too fast at the start. To fix: in a clean bowl, start with one fresh yolk (or another 3 tablespoons of aquafaba) and a teaspoon of mustard, whisk briefly, and then drizzle in your broken mayonnaise as if it were oil — drop by drop at first, then in a stream. The fresh emulsifier rebuilds the structure.
The mayonnaise is bitter. You used extra-virgin olive oil. Olive's polyphenols turn bitter under shear. Use a neutral oil, or use no more than 25% olive oil mixed with a neutral oil.
The mayonnaise tastes flat. Add salt and acid. Mayonnaise needs both, in noticeable amounts.
The mayonnaise won't get thick. Either the yolk was too cold, the oil was too cold, or the bowl was wet. Start over with everything at room temperature in a dry bowl.

Discussion

Hold the finished mayo up to the light. You are looking at a microscopic forest of oil droplets, each coated in a thin protein-lecithin shell, suspended in a small amount of water. The mayonnaise contains more oil than anything else — yet it is not an oil. It is a structure. This is what an emulsion is.

Kitchen Lab 3 — Aquafaba Pavlova (chickpea-liquid meringue)

A demonstration that protein foam is a chemistry, not a single ingredient. Chickpea liquid produces a foam that whips, stabilizes, and bakes into meringue — closely resembling egg-white meringue with a parallel molecular story.

Materials

½ cup (120 mL) aquafaba (the liquid from one 15-oz / 425-g can of chickpeas, drained and reserved — the chickpeas are a free bonus for hummus or salad)
½ teaspoon cream of tartar (or 1 teaspoon lemon juice)
¾ cup (150 g) caster sugar (superfine sugar; if you only have granulated, pulse it in a blender for 30 seconds)
1 teaspoon vanilla extract
A clean, completely grease-free stand-mixer or hand-mixer bowl with a whisk attachment
A baking sheet lined with parchment paper
Optional: whipped cream or coconut cream and fresh berries for serving

Time

About 15 minutes of whipping, 90 minutes of low-temperature baking, then cooling in the oven (typically overnight or 2–3 hours). Total: about 4 hours, mostly hands-off.

Allergen flags

⚠️ Soy in some commercial aquafabas (chickpeas processed alongside soy). ⚠️ None for those without soy-cross-contamination concerns. Egg-version equivalent: replace the aquafaba with 4 large egg whites; same procedure otherwise.

Procedure

Preheat oven to 120°C (250°F). Position rack in the lower third of the oven.
Pour aquafaba into the spotlessly clean mixer bowl. Even a smear of fat on the bowl will prevent foam formation. Add cream of tartar.
Whip on medium-high speed for 4–5 minutes, until the aquafaba turns from clear-yellow liquid to opaque white foam with soft peaks.
With the mixer still running, begin adding the sugar a tablespoon at a time, waiting 15–20 seconds between additions. Slow sugar addition is critical — dumping sugar in collapses the foam. After all the sugar is in, add the vanilla.
Continue whipping until the foam is glossy, holds stiff peaks, and feels smooth (not gritty) when rubbed between two fingers. This is when the sugar has fully dissolved into the foam. Total whipping time: 8–12 minutes.
Spoon or pipe the meringue onto your parchment-lined baking sheet — either as one large pavlova-shape (about 20 cm / 8 inches across, with a slight depression in the middle for filling) or as individual small meringues.
Bake at 120°C (250°F) for 90 minutes. Then turn the oven off and leave the meringue inside until the oven has cooled completely (typically 2–3 hours, ideally overnight). The slow cooldown prevents the dramatic collapse-and-crack of a meringue pulled into room-temperature air.
The finished meringue should be crisp on the outside, marshmallowy in the center (for pavlova) or fully crisp throughout (for hard meringue, baked an additional 30 minutes).
Top with whipped cream (or coconut cream for fully vegan) and fresh berries.

Expected results

A pale, glossy, crisp-shelled disc with a tender slightly-chewy interior. Indistinguishable to most palates from an egg-white pavlova, with a faintly different aroma (very slight bean-y note, masked by vanilla). The structure is real meringue — a protein-stabilized foam set by drying.

Troubleshooting

Aquafaba won't whip past soft peaks. Either the bowl had grease, or the aquafaba is too thin. To thicken aquafaba: simmer it gently in a small pot for 5–10 minutes to reduce by about a third. Cool fully before whipping.
Meringue cracked across the top during baking. Oven was too hot. Drop temperature 10°C / 20°F next time.
Meringue is sticky after cooling. Either it didn't bake long enough, or your kitchen is humid. Bake an additional 30 minutes; store in an airtight container.
Meringue collapsed during baking. Oven door was opened during baking; or sugar wasn't fully dissolved before baking.

Discussion

Compare this meringue to an egg-white meringue (Lab 3 in the egg-version). Most tasters cannot tell the difference once it is topped with cream and fruit. The chemistry uses different proteins — chickpea albumins and globulins, plus saponins — but the structural job is the same: stabilize gas bubbles in a thin liquid film, then lock that film with heat and dehydration. Foam chemistry is general; eggs are one path to it.

Discussion Questions

These are designed for classroom discussion or self-study reflection. Use them to deepen the chapter's content beyond the labs.

The egg white contains seven different named proteins, each setting at a different temperature. Why might natural selection have produced a system with multiple proteins at multiple set points, rather than one protein at one set point? What developmental function might a graded coagulation profile serve for a chick embryo?
Maya's grandmother solved her egg's chemistry without ever measuring a temperature. Maya solved it with a $15 thermometer and three weeks of trials. Are these the same kind of knowledge? Are they substitutable? What is gained and what is lost when one replaces the other?
Mayonnaise is microbiologically stable for about a week refrigerated, even though it contains raw egg. Hollandaise is essentially unsafe to keep more than a few hours. Both are emulsions of fat in egg yolk. What about mayonnaise's chemistry makes it more stable? (Hint: think about pH and water activity.)
The chapter notes that the easiest-peeling boiled egg is one that is 7 to 10 days old. Yet brand-fresh eggs are prized for poaching and frying. Are these contradictory preferences? How would you advise a cook who wants both perfect poached eggs and perfect peeled boiled eggs from the same dozen?
Aquafaba meringue works because chickpea proteins and saponins do something analogous to what egg-white proteins do. But the two foams are not identical. If you served someone an aquafaba pavlova and an egg-white pavlova side by side, what cues might give them away? What does this tell you about the difference between "the same chemistry" and "the same molecules"?
The chapter describes both a fresh egg's high-pH (slightly basic) chemistry slowly drifting toward higher pH as the egg ages, and the lower-pH chemistry of vinegar in poaching water. What are these pH effects doing differently to the egg's proteins? Why does one (aging) help peeling while the other (acid) speeds setting?
Pat's "5 Eggs, 5 Temperatures" demo is, in her words, "a chart that becomes food." Why is the visual and taste version of the protein-coagulation chart so much more memorable than reading about it? What does this suggest about how to teach (or learn) food science generally?
A French rolled omelette is cooked in 90 seconds at high heat. A Korean gyeran-jjim is steamed in 15+ minutes at gentle heat. Both produce edible, delicious cooked eggs. From a protein-denaturation perspective, what is each method doing differently? Where on the temperature chart does each live?
Some traditional cuisines preserve eggs by alkaline treatment (Chinese century eggs / pídàn) — long contact with high-pH solutions chemically denatures the proteins without heat. The product is a textured, savory egg with months of shelf life. How does alkaline denaturation differ from heat denaturation? Why does the texture come out so differently?
The chapter argues that eggs are a "course in a carton." If a cook understands eggs deeply, what other foods become easier to understand? Pick three other ingredients (bread, cheese, mayonnaise, custard, soufflé, ice cream, etc.) and trace what egg-knowledge transfers directly to them.

Advanced Sidebar Expansion — Disulfide Bonds and the Texture of an Old Egg

The chapter sidebar discussed why fresh eggs peel poorly and old eggs peel well. We named pH drift and heat-shock proteins. Here is one more layer for the curious.

Egg-white proteins contain cysteine — an amino acid with a thiol (–SH) side chain. Two thiol groups can join into a covalent disulfide bond (–S–S–) under oxidizing conditions. Disulfide bonds are how globular proteins hold their three-dimensional shape; they are also how, during cooking, those proteins cross-link with each other to form the rubbery network of a hard-boiled egg.

In a fresh egg, the cysteine residues are largely in their reduced (free thiol) state, with the protein structure held by intramolecular disulfide bonds and weaker interactions. In an aged egg, slow oxidation of the whites produces more intermolecular disulfide bonds — bonds between proteins, not within them. The aged white is, even before cooking, slightly more cross-linked.

This has two practical consequences. First, an aged egg's white sets at a slightly lower temperature than a fresh egg's white — the cross-links are partially in place before heat is applied, and the network completes faster. Second, an aged egg's chalazae are weaker (the protein structure that twists them has slowly degraded), which is why old eggs strain through a sieve more easily than fresh eggs.

Egg-white foams care about disulfide bonds too. Whipping introduces shear force that can both break existing disulfide bonds (releasing protein structures to unfold and migrate to bubble walls) and form new ones (cross-linking the walls). The over-whipping problem mentioned in the main chapter sidebar is, mechanistically, when too many new intermolecular disulfide bonds have formed, locking the foam into a rigid, brittle structure that cannot stretch around expanding gas bubbles.

This is also why copper bowls were traditionally used by French pastry chefs for whipping egg whites: traces of copper ions slowly catalyze stable disulfide-bond formation, but only at a moderate rate, producing a foam that is more elastic than one whipped in glass or stainless steel. Modern pastry chefs achieve a similar effect chemically with a pinch of cream of tartar, which slows over-whipping by a different mechanism (lowering pH, which reduces the rate of disulfide cross-linking). Different paths to the same goal: a foam that holds peaks without going brittle.

🥖 Mastery Food Checkpoint

How does this chapter inform the five mastery food tracks?

Bread. Egg-enriched doughs (brioche, challah, panettone) involve yolk fat lubricating gluten, lecithin emulsifying the dough, white proteins adding structure, and carotenoids coloring the crumb. Now you understand why brioche feels like cake — the yolk fat has interrupted the gluten network. Bring this to Chapter 17.
Cheese. The ovalbumin → curd analogy is direct: an egg setting in a custard is closely related to milk's casein setting in cheese. Both are gentle protein coagulation in a water-rich matrix, controllable by temperature and acid. The egg custard you may make this week is a small-scale model of the cheese curd you'll meet in Chapter 32.
Chocolate. Eggs are central to chocolate desserts — mousse au chocolat is whipped egg whites lightening a chocolate-fat base; pâte à bombe is a yolk-and-sugar syrup as the base of buttercream and chocolate ganache lightening; chocolate soufflé is eggs over base. The texture work happens in the egg foam.
Fermented vegetables. Less direct, but: thousand-year egg (Chinese pídàn) is an egg preserved by alkaline action — a parallel preservation chemistry to the fermentation track's acid preservation. Same ingredient, opposite end of the pH scale.
Coffee. The closest connection is egg-cleared coffee — a Scandinavian tradition where a beaten egg is added to ground coffee, and the egg proteins coagulate as the coffee is brewed, dragging fine grinds and bitter colloids out of the brew with them. The chemistry is protein coagulation as filtration.

Mastery Food Checkpoint — Self-Assessment

Choose your track and answer in your own words:

Bread track: Describe how you would adjust a basic bread recipe to make brioche. Which of the egg's roles (binding, coloring, leavening, enriching, tenderizing, moistening) is each adjustment serving?
Cheese track: Explain the mechanism by which a crème anglaise thickens. Compare it to the mechanism by which milk thickens into yogurt.
Chocolate track: Sketch the structure of a chocolate mousse, layer by layer. Identify which layer the egg whites are doing and what they are doing.
Fermented vegetables track: Explain how an alkaline preservation (century egg) and an acidic preservation (kimchi) achieve the same goal — microbiological stability — through opposite pH shifts. What does this say about pH 4.6 (Chapter 33) as a safety line?
Coffee track: Look up a Scandinavian "egg coffee" recipe online. Predict what the egg is doing chemically before you read the explanation.