The Science of Baking: Proteins

Proteins provide structure. The two main structural components in baked goods are eggs and flour.

How are proteins affected during the baking process?

Heat and agitation alter the structure of proteins by breaking their molecular bonds. (There are a couple of other things that break the bonds, but don’t play a big part in baking.) Not a big fan of change, protein molecules want to rejoin their bonds but they’re not too picky so they’ll choose the closest molecule and bond to that one. What we see is coagulation or thickening which gives the body and structure we’re looking for. Gluten isn’t formed until water is added. The addition of water turns gliadin and glutenin into gluten.

Maintaining structure of rich baked goods (with lots of sugar, butter, shortening) at altitude is a challenge, so the main structural components, proteins and carbohydrates, need to be increased.

About Flour

Cake Flour

  • The softest flour
  • Low in protein (6-8%)
  • High in starch
  • Little resistance (i.e. Gluten) results in more height during baking.
    • Protein (eggs) must be added for structure
  • White in color
  • Absorbs liquids faster which results in weaker structure
  • Packs easily
  • Used for making “high ratio” cakes because of its ability to carry large amounts of sugar or shortening.

Pastry Flour

  • Soft flour
  • Cream in color
  • Low protein (7-9%)
  • Used for cookies, pie dough, and pastries high in fat and sugar
  • Compared to cake flour, pastry flour gives ore height than spread because of the increased protein

Bread Flour

  • Hard flour
  • Creamy colored
  • High in protein (11.5-13.5%)
  • Used for breads

High Gluten Flour

  • Hard flour
  • Creamy color
  • High in gliadin specifically, so it is good for strudels, pizza, etc. that require a strong, elastic dough
  • Higher in protein (13.5-14.5%)
  • Mix with bread four for a stronger dough (i.e. Add more glutenin)

All-purpose flour

  • Mix of 40% cake flour and 60% bread flour
  • Creamy in color (unbleached)
  • Used for cakes, pastries, cookies

Clear flour

  • First milling of a “sunburned” kernel. (To continue the egg analogy, this would be like a soft cooked egg.)
  • Very strong protein component
  • Slightly darker cream color
  • Ideal flour for blending flours (for example, blend with rye flour to make rye bread)

Cracked Wheat

  • Still has the clear flour attached

Chlorination of flour makes the dough/batter more acidic, distributes fat more evenly (which creates a favorable cake texture), and it also enhances water absorption. Bromide improves gluten formation and dough elasticity.

About Wheat

There are 2 major classifications of wheat:

  1. Hard Wheat is considered to be “winter grown” and is planted after the first frost of the season. The plant doesn’t germinate and grow until spring/early summer and is harvested in early July. This process ‘leans’ the wheat and results IM more protein and less starch. The flour from hard wheat is white or creamy in color, is sharply granular in feel, does not pack easily, produces the best bread flours and is higher in protein.
  2. Soft Wheat is considered to be “spring grown” and is planted after the threat of frost is gone. It is white in color, soft to the touch, packs easily, and produces the best cakes and pastry because of its lower protein and higher starch levels.

Parts of the wheat kernel:

  1. Bran is the shell surrounding the outside of the kernel. It is a good source of insoluble fiber and B vitamins. Think egg shell.
  2. Germ is the sprouting section of the kernel. It is often removed during processing due to the high fat content which can cause the flour to turn rancid. This is why it is important to keep whole grain flours refrigerated or in a cool room. It is a good source of the B-complex vitamins. Think egg yolk.
  3. Endosperm is the largest part of the kernel and the bulk of the flour. It contains starch and protein elements of the wheat. Think egg white.

Importance of wheat flour:

Wheat flour is the backbone and structure of most baked goods. (Gluten free baking is a whole other subject that I’m just learning about now.) Gluten is the tough, rubbery substance formed when flour is mixed with water. Gluten is made up of two different substances: glutenin and gliadin.

Glutenin gives strength to hold the air through the mixing process or for the gases formed by the action of leaveners. Gliadin is the elastic side of the gluten. Without it, the baked good would not be able to expand or rise during the baking process.

Flour also acts as a binding and absorbing agent in baked goods. It holds the liquids in one mass and affects the keeping quality of baked goods through its ability to retain moisture. The higher the protein flour the higher its ability to absorb water.

Eggs- the incredible edible egg!

White (%)
Moisture 90.00% 55.00%
Protein 10.00% 55.00%
Lipids 0.00% 25.00%
Carotenoids 0.00% Trace

Eggs are composed of 2/3 white and 1/3 yolk.

What do eggs do in baked goods?

Eggs have 3 main functions in baked goods:

  1. Foaming- the incorporation of air into a batter.
  2. Emulsification: the stabilization of one liquid in another that wouldn’t naturally mix together (i.e. Oil and water will emulsify easier with the help of mustard in a vinaigrette.)
  3. Coagulation- the conversion of the liquid egg into a solid, which binds together other ingredients.

Eggs are very important in baking at sea level and are also a big help in successful high altitude baking. Eggs are known as “tougheners” because the proteins in the white and yolk provide structure. They’re also known as “tenderizers” because of the lipids and emulsifiers in the yolk.

In terms of structure, egg whites have the most, followed by whole eggs and then finally egg yolks. Eggs provide structure to baked goods because of the aggregation (also known as thickening or gelling) of the protein. Think of the proteins as tightly wound springs. As the eggs are cooked the protein unwinds and then reconnects with other proteins to give structure to baked goods and custards. You can maximize the amount of structure provided by egg whites if you allow them to warm up a bit. The proteins will begin the process of unwinding slowly. Just like athletes need to warm up before a game for optimal performance, egg whites will experience the same benefits. You will also get a more stable egg white/meringue if you start whipping on a lower speed because more uniform air cells will be formed. Replacing ~25% of the weight of the egg whites with water creates a more flexible foam less prone to ove-rbeating and will foam up faster.

There are other factors that affect how the egg proteins will coagulate and hence the type of structure formed: rate of cooking, amount of acid, and amount of tenderizers.

  • The slower an egg is cooked, the smoother its texture will be which is why many recipes for custards and puddings call for the use of a bain marie or double boiler. A bain marie or double boiler also help with even cooking and help prevent overcooking. If eggs are over cooked, the thickening/gelling disappears into a chewy mess and the proteins tighten. The custard will look lumpy and watery because the proteins are squeezing together and pushing the water out.
  • According to Alton Brown, scalding milk for a custard creates a smoother custard- though nobody knows exactly why that happens.
  • Adding acid to eggs will cause more coagulation and lowers the temperature at which the eggs coagulate. Egg coagulation at lower temperatures is especially beneficial to high altitudes because our water doesn’t boil as hot.
  • Adding fats and sugars will result in a more tender baked good as they inhibit some of the coagulation.
  • Sugar is a wily beast when interacting with eggs. It is a tenderizer because it is hygroscopic. If the sugar steals the water from the protein, the protein will be weaker. Sugar, however, is also slightly acidic which helps strengthen the protein in the eggs which is why meringues hold their shape better than plain whipped egg whites and why sweet soufflés are easier to handle than savory ones. Sugar also helps stabilize meringues because it dissolves in the water of the egg whites, coats the proteins and slows down drying process.
  • Egg whites reach their maximum volume at 8x of their original volume; whole eggs can reach 4x their original volume; and egg yolks can reach 1 _x their original volume.

Eggs Sizes (from the USDA)

Pee wee 15 1.
Small 18 1.5
Medium 21 1.75
Large 24 2
X-Large 27 2.
Jumbo 30 2.

More Egg Pointers:

  • Fresh eggs have prominent chalazae, thick whites, and perky yolk.
  • As the egg ages, in today’s refrigerated environment, it will slowly loose moisture. Dehydration is more likely to occur than actual spoilage.
  • The weights for individual eggs set by the USDA are based upon the total weight of a dozen eggs; ie the eggs within a single dozen can have varying weights but the total meet USDA requirements. So, it is important to weigh eggs as well because their weights can vary and can decrease as the egg ages.
  • Adding an extra egg yolk will create more puff and less spread to cookies during baking. An acidic batter will set faster but have less browning. Baking soda will neutralize some of the acid and thus will help with browning.
  • To make a dry cake more moist, substitute 2 to 2. egg yolks for 1 whole egg.
  • According to Rose Levy Berenbaum, author of “The Cake Bible,” acidic batters produce a sweeter, more aromatic quality in cakes. In his baking cookbook, Alton Brown notes that adding acid proves flavor, changes the crumb of baked goods and they brown and retain moisture better, which is very beneficial at high altitudes.


  • Always use clean utensils and bowl. Fats inhibit volume.
  • Egg whites should be at room temp for text volume
  • Add acid once egg whites are foamy and starting to get volume
  • Sugar should not be added too soon or too fast
  • Allow egg whites to whip to at least 4 x the original volume before adding sugar
  • Add sugar in a slow steady stream
  • Do not over whip your egg whites. They will lose volume and deflate, and will be hard to incorporate because they become dry and lumpy

Peaks achieved in meringues:

  • Soft: too little air, loss of volume, curls when checked
    not desirable except when meringue will be incorporated into something
  • Medium: proper amount of air- ‘7’ shape when checked
  • Stiff: shiny, stand straight when checked
  • Dry: over whipped, too much air, loss of volume, looks clumpy, not desirable.

Meringue Types

  • French or Common
    • Least stable
    • Can be gritty
    • Quickest method
  • Swiss
    • More stable than common meringue
    • Whites and sugars are heated together
    • Whip until cool
  • Italian
    • Most stable
    • Considered the finest
    • Takes the longest amount of time

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