Flour is one of the pillars of classical baking. As a kid, it was my least favorite ingredient. Everything tasted so wonderful until my mother went and dumped in two cups of flour and the whole thing went to pieces. The batter got all thick and tasted grainy, the eggs, butter, and sugar were so sadly overwhelmed, all my delicious batter was slowly losing its perfection and still, she kept on pouring in flour. You can see I was staunchly pro-batter as a child (I still am); nothing ever tasted half as good baked as it did raw.
I still love batter and dough, but I’ve learned to appreciate the final, baked product a lot more, and I’ve come to terms with the necessary addition of flour. There is a reason, a very good, scientific reason, that none of my early experiments baked very well (despite tasting heavenly as batter).
I. The Anatomy:
Flour is made from finely ground cereal grains, most commonly from wheat.
It contains three key molecules that are essential to its role in baking: starch, glutenin, and gliadin.
Starch – is a large glucose (sugar) complex. It’s a polysaccharide (a long carbohydrate molecule) also known as “amylum”. Human digestive systems have a very difficult time processing and digesting starch unless it is cooked. Starch is commonly found in plants and provides rigidity to plant cell structure; it does the same thing in baking, creating structure in pastries.
Glutenin – the major source of protein found in wheat flour. It is a protein complex with high molecular weight and low molecular subunits. It combines with gliadin to form gluten.
Gliadin – is a prolamin (a group of plant storage glycoproteins) found in wheat and other grasses. It is only soluble in alcohol and can serve as a method for transporting fragile enzymes by protecting them from digestive acids. It acts as a leavening agent and gives pastries their structure.
Gluten – a protein complex found in grains such as wheat, rye, and barley. It is formed when glutenin combines with gliadin and forms molecular sub-networks. This combination happens when you knead flour into dough. When gluten is leavened with sugar, carbon dioxide forms bubbles, causing the dough to rise.
Flour is a true multi-tasker. It makes dough elastic, helps build structure, and acts as a leavening agent.
Kneading flour creates gluten, and the more the batter is mixed, the more the gluten builds up (thats why over mixing baked goods like cookies can lead to an overly-tough final product). Gluten adds chewiness and that’s why tougher baked goods (like bread) use flour with higher gluten content than more tender baked goods, like pastries. Fats and sugars prevent gluten formation (thereby increasing tenderness and decreasing structure rigidity).
Flour is a toughener; the more flour, the more proteins, and the more proteins, the stronger the structure of the pastry becomes. Baking hardens gluten, which forms the structure in pastries. Flour is integral in the formation of structure (that’s why flour less cakes are often soft, ‘fallen’, and/or flatter) as well as in the leavening process. Without flour, you can get your pastry to puff up, but you won’t be able to get it to stay up.
Carbon dioxide is released from several chemical reactions (sugars fermenting, catalysis of chemical reagents like baking soda, etc.) during the baking process. The carbon dioxide bubbles are trapped by the starch and gluten in flour, making the batter/dough rise. However, the networks created by this process absorb water, leading to a drier pastry.
Too much flour and your pastry will be too dry and crumble, however, not enough flour and your pastry will fall (or with cookies, they’ll spread uncontrollably).
All-purpose flours have varying protein content, which means that they will each affect your pastry differently. The higher the protein content, the tougher the baked good, and the less protein, the more tender. To test the protein of your flour, scoop two cups of flour into one cup of water and stir. Flour high in protein will absorb the water and become dough very quickly, flour with less protein won’t combine until you add more flour.
Cake flour is high in starch, low in protein, and is very finely milled. It’s specially made to carry large amounts of sugar and fat without collapsing. It’s also been heavily bleached to make it lighter in color and to break down the protein. To make cake flour yourself, mix 3/4 cup of bleached all purpose flour with 2 tablespoons of cornstarch.
To make your pastry lighter, you can sift your flour. The idea is that during shipping and packing, flour compacts, which means that you might use too much on accident and that, if the flour is packed too dense, it won’t lift your pastry properly. It’s also considered an important step for better dispersing your leavening agent (ie. baking soda). However, some bakers maintain that sifting your flour doesn’t actually help distribute the leavener any better.