CONCEPT 20: STARCH KEEPS EGGS FROM CURDLING

Question 1

How does stirring affect the strength of protein networks in eggs for custards? What does this mean?

Answer 1

Besides preventing overcooking or burning, it reduces the extent to which the proteins bond into a solid mass. This means that stirred custards form a thinner sauce while oven-cooked form solid gels.

Question 2

How do starches affect the temperature of coagulation?

Answer 2

Starch granules release spindly threads of amylose that interfere with the cross-linking of proteins, increasing the temp at which eggs coagulate.

Question 3

Name two starches used.

Answer 3

Cornstarch and flour.

Question 4

What dishes are starches important for?

Answer 4

Things like quiche, puddings, pastry cream and hot soup to keep wisps of raw egg added feathery and fine.

Question 5

TEST KITCHEN: FRENCH PASTRY CREAM WITH AND WITHOUT CORNSTARCH.

Answer 5

W/O cornstarch Cream with cornstarch thickened into a creamy, smooth, pudding-like consistency; starch less broke into two phases, becoming a thin, watery base with bits or curdled egg throughout.

Question 6

Why would you brush a raw quiche dough with egg white?

Answer 6

To seal any possible cracks.

Question 7

Do onions make eggs curdle? How?

Answer 7

Yes, the acids they release alter electrical charges on the egg proteins, causing them to clump.

Question 8

Does starch prevent onions from curdling eggs in a quiche?

Answer 8

Yes, starch granules act as a barrier between the proteins, which prevents them from squeezing out liquid.

Question 9

Good ratio of eggs to dairy for quiche filling.

Answer 9

9 eggs to 3 cups of dairy.

Question 10

What is a traditional thickener in hot and sour soup?

Answer 10

Cornstarch

Question 11

If you can’t find Chinese black vinegar what’s a good substitution?

Answer 11

Equal parts of red wine and balsamic vinegar.

Question 12

How does cornstarch help keep pork tender?

Answer 12

Cornstarch clings to the meat during cooking, creating a protective sheath that slows the loss of moisture.

Question 13

Hot does the heat from chiles and pepper differ?

Answer 13

Unlike chiles, pepper delivers direct spiciness but doesn’t leave a lingering burn in its wake.

Question 14

What is Chinese black vinegar made from?

Answer 14

Toasted rice

Question 15

Wood ear mushrooms are also known as what?

Answer 15

Tree ear or cloud ear.

Question 16

What are lily buds and golden needles?

Answer 16

Dried buds of tiger lily flower.

Question 17

Describe the taste and texture of bamboo shoots.

Answer 17

Tangy and mildy crunchy.

Question 18

Should you press tofu for a soup? Why?

Answer 18

Yes, spongelike tofu contains a lot of moisture; weighting it beneath a heavy plate yields firmer, cleaner tasting cubes.

Question 19

When adding egg to a soup, what components help creates fine, feathery shreds and not muddy the appearance?

Answer 19

Acid, cornstarch and a calm surface.

Question 20

How do acid and cornstarch help eggs create a fine, feathery texture in soup?

Answer 20

The vinegar neutralizes some of the electrical charges so they bind and bond together; cornstarch stabilizes the liquid proteins, preventing them from contracting excessively in hot liquid.

Question 21

What is referred to as dark or Asian sesame oil?

Answer 21

Toasted sesame oil

Question 22

What is toasted sesame oil produced from?

Answer 22

Deeply roasted sesame seeds.

Question 23

Does cold-pressed sesame oil have a large flavor and aroma?

Answer 23

No

Question 24

What is toasted sesame oil usually used for?

Answer 24

Flavoring agent for distinctive character rather than a cooking oil.

Question 25

Can cold-pressed sesame oil be used interchangeably with other vegetable oils?

Answer 25

Yes

Question 26

Why should toasted sesame oil only be purchased in a tinted glass and stored in the refrigerator?

Answer 26

It is particularly prone to damage from heat and light.

Question 27

Do white and green area of scallions differ in texture and flavor?

Answer 27

Yes

Question 28

Describe taste of scallions.

Answer 28

Green portion has grassy notes and a peppery bite; white had a delicate, sweet taste similar to shallots.

Question 29

Is the texture of scallion sections different after cooking?

Answer 29

Yes, the whites softened nicely while the greens took on a limp texture; only use greens as a garnish.

Question 30

Should you chop scallions in advance? Why?

Answer 30

No, a dull, soapy flavor takes place of the sweet onions flavor when pre-chopped and left to wait.

Question 31

Flour is 75% what?

Answer 31

Wheat starch

Question 32

What does chocolate pudding usually suffer from?

Answer 32

A dearth of chocolate or grainy texture that’s caused by too much cocoa butter.

Question 33

Should you add cornstarch or eggs to a pudding?

Answer 33

Both, pudding made with cornstarch only is a hollow affair; not as texturally dense and creamy as we prefer–eggs add richness and body.

Question 34

Can you add unlimited amounts of bittersweet chocolate in pudding to increase its flavor? Why?

Answer 34

No, manufactured chocolate’s fat is made to stay solid at room temp and melt in your mouth. When the cocoa butter resolidifies, its crystalline structure is reorganized and becomes more stable; melts much more slowly. In high amounts it will create a grainy texture.

Question 35

Does cocoa powder have less cocoa butter than bittersweet chocolate?

Answer 35

Yes, it has far less cocoa butter.

Question 36

What adds more chocolate flavor without increasing overall amount of cocoa butter?

Answer 36

Cocoa powder

Question 37

How can you thicken pudding with chocolate?

Answer 37

Using chocolate with a higher cacao percentage will result in a thicker pudding; a higher cacao % means more cocoa butter and cocoa solids, both of which act as thickeners.

Question 38

Compare cacao % in chocolate to fat % in cream.

Answer 38

Just as more fat in heavy cream makes it thicker than milk, a higher % of cacao makes it thicker as well.

Question 39

What does expresso powder do to chocolate?

Answer 39

A little bit of coffee flavor serves to reinforce, but not compete, the flavor of chocolate, enhancing its roasted undertones.

Question 40

Why is pastry cream considered an anomaly among custards?

Answer 40

Overheating typical leads to curdling; however, it’s vital to bring pastry cream to a boil–doing so sets the egg and activates (gelatinizes) the starch, ensuring proper consistency.

Question 41

What ingredient makes pastry cream an anomaly? Why?

Answer 41

An enzyme in the yolks called amylase can break down the starch and make pastry cream runny; brining it to a boil destroys the amylase.

Question 42

When it’s hot enough, 3 or 4 bubbles will burst on a pastry creams surface. What is the temperature?

Answer 42

200 degrees

Question 43

Which thickener is less potent, cornstarch or flower?

Answer 43

Flour is a less potent thickener.

Question 44

What happens chemically when starch is heated in water?

Answer 44

The granules absorb water, swell, and eventually burst, releasing a starch molecule called amylose that diffuses through the solution, trapping additional water and forming a gelatinous network.

Question 45

Why does cornstarch contain more amylose than flour?

Answer 45

It is a pure starch.

Question 46

If pastry cream isn’t heated enough, how does amylase ruin it?

Answer 46

Weakens the starch gels so the custard never fully sets up.

Question 47

Better thickener for pastry cream, cornstarch or flour? Why?

Answer 47

Flour contains proteins and lipids that dilute its capacity to form starch gels, so that more of it is needed for thickening. But these components also act as binders, keeping water trapped and ensuring it’s only used for thickening.

Question 48

What happens is pastry cream is heated too much?

Answer 48

The starch granules can burst.

Question 49

What does over-whisking do to pastry cream?

Answer 49

Break the bonds of starch gels and thin it out.