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THE SCIENCE OF GOOD COOKING > CONCEPT 21: WHIPPED EGG WHITES NEED STABILIZERS > Flashcards

CONCEPT 21: WHIPPED EGG WHITES NEED STABILIZERS Flashcards

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1
Q

Describe whipped egg whites.

A

A billowy mound of cloud-like foam.

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2
Q

How do egg whites go from liquid to foam when whipped?

A

As an egg white is beaten, its protein unfold and bond to create a mesh-like network that coats and reinforces the surface of air bubbles produced in the water from egg whites (90% H2O). The unfurled proteins increase viscosity of the water surrounding any air bubbles, enhancing their stability.

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3
Q

What happens if egg whites are under-beaten?

A

Foam won’t be stable.

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4
Q

What happens if egg whites are over-beaten?

A

The foam will become too rigid and rupture, squeezing out the liquid contained in the whites.

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5
Q

What will yolks do to egg whites when creating a foam?

A

They will coats the proteins, much like in a custard, and prevent them from unfolding and bonding.

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6
Q

What do oils and fat do to the air bubbles of a foam?

A

Fats and oils take up valuable space on air bubbles, disrupting the network of protective proteins and causing foam to deflate.

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7
Q

Why don’t foams last?

A

Water eventually succumbs to gravity and begins to drain away.

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8
Q

Will starch help stabilize egg white like a custard?

A

No

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9
Q

What two ingredients help stabilize whipped egg whites?

A

Sugar and cream of tartar.

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10
Q

What two ways does sugar help stabilize egg white foam?

A

It slows the unfolding of egg proteins, delaying the formation of foam and protecting against over whipping. Two, it dissolves in the liquid surrounding the air bubbles, forming a thick and viscous syrup that is slow to drain.

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11
Q

Can sugar be added in the beginning of whipping? Why?

A

No, it interferes with the protein’s ability to cross-link; fewer proteins will bond and trap air, resulting in a foam that is less voluminous.

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12
Q

What happens if you add sugar too late?

A

Sugar has less water to dissolve in, creating a gritty texture and a tendency to form drops of sugar syrup during baking.

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13
Q

When is the right moment to add sugar?

A

When the foam is frothy and bubbly but not quite firm enough to hold a peak; right before soft peak.

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14
Q

How does cream of tartar create better foam?

A

It’s an acid that alters the electrical charge on the proteins of egg whites, reducing the interactions between protein molecules.

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15
Q

Does whipping take longer with cream of tartar?

A

Yes, but produces a much more stable foam.

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16
Q

Why are stabile foams important?

A

Whipped egg white can revert, at least partially, to their liquid state over time. This is what happens when the meringue topping on pie “weeps.”

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17
Q

TEST KITCHEN: FOAM WITH CREAM OF TARTAR AND WITHOUT.

A

Regular foam lost 23mL of water in 60 minutes; cream of tartar lost less than half of that #, 9mL.

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18
Q

How can you minimize stickiness of meringue cookies on a humid or rainy day?

A

Allow meringues to cool in a turned-off oven for an additional hour.

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19
Q

Two basic ingredients in meringue cookies.

A

Egg whites and sugar.

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20
Q

How many types of meringue are there? What are they?

A

Italian, Swiss and French.

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21
Q

What is an Italian meringue?

A

Hot syrup is poured into the egg whites as they are beaten.

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22
Q

What is a Swiss meringue?

A

Heats the egg whites with the sugar.

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23
Q

What is a French meringue?

A

Egg whites are whipped with sugar alone.

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24
Q

What is the difference between meringue cooking when using French instead of Italian?

A

Italian meringues are dense and candy like.

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25
Q

What happens to meringues as they bake if sufficient sugar isn’t added? Why?

A

Without sufficient sugar, the meringues will lose moisture too quickly and collapse.

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26
Q

What are the twin-stabilizers for meringues?

A

Sugar and cornstarch.

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27
Q

To guarantee uniform shape, what should you use?

A

Piping bag

28
Q

Substitute for pastry bag?

A

Zipper-lock bag with end cut off or parchment paper.

29
Q

Oven temp and techniques for meringue cookies.

A

225 degree oven for an hour, followed by another hour in the turned-off oven.

30
Q

In their raw state, tiny bubbles that form a meringue get their structure from what two things?

A

Cross-linking of egg white proteins and the water that occupies virtually all the space between the bubbles.

31
Q

What is happening as a meringue bakes?

A

Its moisture slowly evaporates, weakening its structure. At the same time, ovalbumin is becoming stronger by bonding with other proteins, providing additional structure for the foam.

32
Q

What does sugar have a tendency to hold on to as meringues bake? How does this help?

A

Sugar stops meringue from drying out too quickly, which causes cookies to collapse before ovalbumin has time to strengthen.

33
Q

What does cornstarch add to meringue cookies?

A

It shares the water clinging property of sugar and allows you to cut back on sugar if overly sweet; it doesn’t compromise structure.

34
Q

Recipe for meringue cookies.

A

3/4 C (5 1/4oz) sugar
2 TBSP cornstarch
4 Large egg whites

35
Q

If sugar is lumpy should you break it up with grease-free fingers?

A

Yes, any residual fat from butter or chocolate might hinder whipping the whites.

36
Q

Brown sugar offers sweetness and what?

A

A hint of smokiness from the molasses.

37
Q

What ingredient in brown sugar is slightly acidic? What could this eliminate in making foam?

A

Molasses could eliminate the use of cream of tartar.

38
Q

When folding egg whites with chocolate to bake, what happens when nothing has been added to them?

A

They collapse under the chocolates weight, giving the cake a dense, brick-like structure.

39
Q

When folding egg whites with chocolate to bake, what happens when they’ve been beaten almost rigid?

A

This will make the cake unappealingly dry; beating them will only make the cake more dense.

40
Q

When is sugar added if the final product should be soft peak instead of stiff?

A

Add 1/2 after it becomes frothy (30 sec) and combine; add the other half after combined.

41
Q

What happens when mousse cake is baked at 350?

A

It turns into a giant mushroom that collapses after cooking.

42
Q

What happens when mousse cake is baked at 300?

A

Causes the cakes exterior to be overdone with a raw center.

43
Q

What’s the right temp to bake a mousse cake?

A

In a water bath at 325 degrees.

44
Q

Safest way to separate eggs?

A

Cracking then in a smaller bow, while cold, and then separating.

45
Q

Should plastic wrap on covered, cracked eggs be touching their tops? Why?

A

Yes, so they don’t dry out.

46
Q

Cream of tartar is also known as what?

A

potassium bitartrate or potassium acid tartrate.

47
Q

Cream of tartar is a byproduct of what?

A

Winemaking process

48
Q

Two main ingredients in baking powder.

A

Cream of tartar and baking soda.

49
Q

Cream of tartar’s acidic nature does what to egg whites?

A

Lowers the pH, altering the electrical charge on proteins, encouraging them to unfold; thus creating more volume, greater stability and a glossier appearance.

50
Q

Why is Italian meringue a better choice for lemon meringue pie?

A

The hot syrup cooks the whites and transforms them into a soft, smooth meringue that is stable enough to resist weeping while baking; French doesn’t always cook through and weeping is a greater risk.

51
Q

Does angel food cake use oil or butter?

A

No

52
Q

What can make an angel food cake somewhat heavy?

A

Sugar, even if it’s confectioners’ or granulated.

53
Q

How to you avoid an acceptably heavy angel food cake?

A

Process granulated sugar in the food processor until powdery; it will dissolve much faster and won’t deflate the egg whites.

54
Q

How can you get away with sifting dry goods for angel food cake just once?

A

Process flour with half the sugar to aerate.

55
Q

How many batches should you add flour into egg-white foam? Why?

A

Three batches won’t deflate the egg whites.

56
Q

How should you cool and angel food cake? Why?

A

Angel food cake should be flipped upside down so they aren’t crushed by their own weight.

57
Q

What is bouillie?

A

A paste made from flour and milk.

58
Q

When folding the foam into a soufflé, what makes them more resilient to a heavy hand?

A

Sugar makes the foam more stable.

59
Q

What technique give a soufflé a high, even rise? Why?

A

After pouring, trace a circle in the batter with your finger, 1/2 inch from the edge of the dish; it breaks surface tension.

60
Q

Describe the taste of a finished soufflé.

A

Very creamy in the middle and firm around the outside, almost like a pudding cake.

61
Q

Good indication a soufflé is done cooking.

A

The center isn’t completely solid or liquid-y, but still quite loose and very moist. Once you can smell a soufflé it’s about ready to come out.

62
Q

Do copper bowls help make whipped egg whites stable?

A

Yes

63
Q

What do “copper egg whites” do for a soufflé?

A

Soufflé has greater volume, flavor is less eggy and a light golden crust.

64
Q

Science of copper bowls and egg whites.

A

When whipped, copper ions combine with conalbumin and slow the coagulation process; foam is more stable because it takes longer to whip. Because the foam is more stable, it can better tolerate expansion in the oven.

65
Q

Why does a soufflé made with copper taste less eggy?

A

Copper binds with sulfur atoms contained within some of the egg proteins. Since eggy flavor comes from the breakdown of these proteins (and the rustling release of sulfur-containing compounds), it is more stable and less eggy.

THE SCIENCE OF GOOD COOKING (61 decks)

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