Essential Ingredients | Flour

The four ingredients that make up the majority of baked goods are flour, sugar, fat, and a leavening agent. These ingredients work together, creating a series of chemical and biological reactions to create an immense range of textures, flavors, smells; even emotions. Memories of childhood pastries – a favorite birthday cake; the flaky, buttery, perfectly golden brown of a croissant; the sour tang and chewy texture of fresh baked sourdough bread. All contain some combination of flour, sugar, fat, and a leavening agent. Baking is a game of ratios. One and a quarter cups flour, two tablespoons butter, two teaspoons baking soda, one teaspoon sugar, one cup milk. Add the heat from a hot cast iron and a scoop of batter and you have pancakes. How ingredients are incorporated – what temperature is required of the raw ingredients, in which order and proportion, which technique is used – whipping, stirring, folding, sifting – create such different masterpieces from the light and fluffy angel food cake to the chewy crumb and dense crust of rustic bread. This series of posts will address these four basic ingredients – their different forms, combinations, and resulting reactions – as well as exploring additional ingredients such as chocolate, vanilla, spices, and fruits essential to the well rounded bakers pantry.

FLOUR

Flour is the primary structural background of baked goods, most commonly harvested from wheat (Triticum spp.). Genetic analysis suggests  wheat was first cultivated in the near East regions of Turkey, Syria, and Iraq with the earliest carbon-14 dating of wild emmer found in northern Jordan as far back as 9600 BC (Wikipedia). Processing of wheat flour removes the hull and the germ, and the endosperm is ground into fine flour. Whole wheat flour has had a measure of the germ left intact which boosts nutritional content by retaining fiber and natural oils, but often spoils faster than more processed unbleached flour as the oils can go rancid more quickly.

The primary components of flour are gluten and starch. Gluten is made up of the proteins gliadins and glutenins. When these proteins  are combined with water and undergo stretching and other mechanical mixing and manipulation, gluten proteins form which creates a web of elastic strands. Wheat starch is the most common carbohydrate in the diet and when raw, the human digestive system has trouble breaking down the structure. When cooked, starch digestibility is increased, but the result produces a gelatinous structure in the presence of water. In baking, the addition of sugar interferes with the starch gelatinization by absorbing water and improving the texture. There are situations when the gelatinzation from starch is desirable and flour is often used as a thickener in sauces (such as gravy) and pie fillings where starch improves the texture.

There are two basic categories of wheat based on protein content: hard wheat (higher protein content) and soft wheat (lower protein content). Hard wheat is often labeled as bread flour and used for baked goods that require a strong, flexible gluten structure. Soft wheat is used in cake flour when a lighter, more tender product is desired. All purpose flour is a blend of hard and soft wheat and each producer has its own proprietary blend.

TYPES OF FLOUR

Depending on the recipe and desired results, an appropriate amount of protein is needed to achieve the right texture. Since protein percentage is generally not listed on the packaging, but necessary to know, you can figure out the protein content by dividing the number of protein grams per serving by the number of total grams in a serving. The following is a list of some common types of flour.

Cake Flour

Cake flour has the lowest percentage of protein ranging from 5% to 7%. Many cake recipes call for cake flour to keep the texture (or crumb) light and tender. Gluten formation is present to support the structure of the cake and trap the air bubbles formed from the leavening, but the reduced protein content keeps the cake from becoming too chewy and dense from over mixing the batter. Since liquid and mechanical action aid in gluten formation, less gluten in the flour will form if over mixed. If cake flour is not stocked in your pantry, but called for in a recipe, a substitution can be made from 7/8 cup of all purpose unbleached flour and 2 tablespoons of cornstarch for each cup of cake flour. Cornstarch will add starch while reducing the ratio of gluten-forming proteins. Cake flour is always bleached with chlorine which disrupts gluten formation, but promotes starch formation and allows the flour to hold more liquid than it otherwise would. The bleaching procedure also decreases the pH, making it more acidic. Higher acidity aids in maintaining the structure of cakes when made with egg whites (such as angel food cakes) which helps the foam structure of the beaten egg whites to set when heated, resulting in a firm and tender cake.

Self-Rising Flour

Self-rising flour is popular in the southern United States and England and has the addition of 1 1/2 teaspoons of baking powder and 1/2 teaspoon of salt per cup of flour. It is a medium protein flour with 7% to 11% protein, but should only be used in recipes which call specifically for self-rising flour.

All Purpose Flour

Protein content in all purpose flour ranges from 7% to 12% protein. Always use unbleached all purpose flour. Historically, flour was made in small batches and – after milling – the flour was left to sit so protein could develop and the color would naturally bleach from the grains. Lighter colored flour was more desirable because it meant the flour had been given time to develop, so chemical bleaching was used to lighten the flour. Chemically bleached flours have a lower protein content since the aging process is reduced and, also, because the bleaching agents destroy some of the protein formation. Bleaching agents used are generally benzoyl peroxide (just like the acne medication) or some type of chlorine. All purpose flour is what is sold in every grocery store across the country and each manufacturer has a proprietary blend which comes with a range of protein content. Major name brands have a more consistent protein content (Gold Medal is a good choice and maintains a  range of 10% to 11% protein).

Bread Flour

Bread flour contains the highest amount of protein of any type of flour. Gluten formation is essential to the structure of bread and the leavening agent (often biological yeast) which creates carbon dioxide and alcohol as byproducts of consuming flour and sugar. The gluten must be able to stretch as gas is produced within the structure of the dough coagulate in the heat of the oven without collapsing as it cools.

GLUTEN DEVELOPMENT

Formation of immensely strong strands of gluten is created by heat and mechanical stretching in the form of kneading. Heat encourages the activity of yeast organisms, and stretching creates the bonds of gliadins and glutenins. The addition of liquid hydrates the strands which begin to form a tangled net. As the dough is worked, the gluten strands create long, twisted chains which are strong enough to be stretched, but spring back after stretching. When the dough is baked in the oven, final coagulation of the strands occurs which allows the pastry or bread to hold its shape and prevents it form collapsing as it cools. Several factors can influence gluten development and techniques can be applied to change the texture and structure.

Choice of flour is important since different flours have different ratios of protein. Altering the choice of flour can greatly influence the production of gluten in the recipe.

Dough manipulation (kneading) more or less is one of the primary factors that produces gluten. Following the addition of liquid, kneading creates the gluten structure in bread. If dough is not kneaded, very little gluten will form and the loaf will be dense and heavy. Pie dough and cake batter must not, however, be overmixed or too much gluten will adversely affect the texture of the dough.

Controlling the amount of liquid in the recipe also has an influence on gluten production. Protein molecules must be hydrated before gluten can form. Variations in protein in the flour actually affect how much water can be absorbed into the structure of the dough so flour with less protein content will absorb less water, creating a soupy batter if too much water is added, while higher content flour absorbs more water. When the protein structure is overwhelmed by liquid, the proteins are diluted which affects their ability to bond and strengthen. Some bread recipes – such as Italian ciabatta – call for a wet dough and the resulting loaf is a flat bread with large holes in the chewy crumb. If you change the type of flour you use, you may need to adjust the water content to maintain structural integrity in the pastry or bread.

Temperature of the liquid influences gluten production as well. Warm liquid hydrates proteins more quickly, while cold liquid delays hydration. Pay attention to the temperature of ingredients called for in your recipe (room temperature eggs or cold water). Pie dough is created with cold ingredients which delays gluten formation, leading to a flaky, tender dough.

Fat content interferes with gluten formation because it coat the strands of protein and reduce hydration from water. If protein strands aren’t hydrated, they won’t bond and form long strands of gluten. This type of interference is called “shortening.” Pastries that are shortened often have a very delicate crumb and high fat content – like shortbread cookies.

Sugar works in tandem with the amount of liquid in a recipe because it absorbs liquid readily – effectively robbing the protein strands of sufficient liquid to hydrate. Sugar acts to moisten and tenderize recipes – as well as adding sweetening.

Ultimately there are several factors influencing how what flour acts in recipes from the molecular make-up of the flour to the environment in which the flour is worked. Hopefully you have learned from this article and can apply this to your next baking project. Please let me know if this information was useful to you, or if there was a difference in your approach to baking.

XOXO

References

Dresser, Keith. “Stocking a Baking Pantry.” Cook’s Illustrated. 85 (2007): 16-17. Print.

Mushet, Cindy; Sur La Table. The Art and Soul of Baking. Pp. 20-22. Andrews McMeel Publishing, LLC. Kansas City, MO. 2008. ISBN: 978-0-7407-7334-1

Picheca, Christine. “Unbleached Flour vs. Bleached Flour – What’s the Difference?.” The Foodie-File: Sleuthing for Food and Drink in Canada. Very Good Food, 05 Dec 2009. Web. Web. 29 Jan. 2013.

Photo credits:

Flour photo // Wheat photo

Lemon Layer Cake with Fluffy Icing | Or: Everything You Learned in High School Chemistry is Actually Important

Today it snowed. Actually, it’s been snowing since Thursday night and the driveway has now been plowed twice, thanks to my tenacious husband. I, on the other hand, decided to bake. The chemistry of baking is incredibly interesting to me. I love that a combination of fat, sugar, and eggs – tempered and heated to 170° – creates custard. What exactly does that? What causes the difference in how pastries bake up when liquid is added to dry ingredients, versus when dry ingredients are added to wet ingredients?

Publications from Cook’s Illustrated have filled some of the void in my search for why a certain process must proceed according to certain predetermined steps, but I still have quite a few questions. Today, I decided to tackle Lemon Layer Cake with Fluffy Icing, compliments of The Cook’s Illustrated Cookbook. This cookbook is a bible. I just love it.

This particular recipe includes a white cake, lemon curd for the filling, and a fluffy white icing made with egg whites – kind of like a shiny meringue, like marshmallow. Sounds easy enough. The recipe was fairly involved and, with the three separate components, took me several hours to complete.

I started with the lemon curd. This was a fairly basic curd recipe, but included an additional 1 tsp of gelatin to tighten up the texture after it cooled and make it more spreadable as a filling.

While the lemon curd was setting up in the refrigerator, I baked the cakes. This cake recipe was a little different than the traditional white cake recipe in two ways. First, it omits the egg yolks from the egg component, going with six egg whites instead. Not that unusual, since egg yolk tends to lead to a more rich and heavy batter. The second difference was to combine the dry ingredients, and then beat in the softened butter to the dry ingredients before adding the wet ingredients.

This approach reminded me of a pie crust I make where the butter is cut into a portion of the flour, followed by the addition of the rest of the flour. The reason for this is the reaction of water and flour to create gluten strands. In a pie dough recipe, you are looking for the perfect combination of tender flakiness and sturdiness, and this depends on the amount of flour that reacts with the water to create gluten. By blending the flour and butter to a portion of the total flour first, the butter creates a protective, hydrophobic (won’t absorb water) coating around the flour and reducing the gluten-producing reaction of flour and water. Later in the pie dough recipe, the remaining flour is added along with water, effectively controlling the amount of gluten produced and keeping the pie dough from becoming to tough.

Back to the cake! Since this cake is supposed to be light and tender, the replacement of egg yolk with egg whites makes it light and fluffy, but the addition of softened butter to the dry ingredients also helps to keep it light by reducing the amount of naked flour which could create too much gluten and make the cake tough. This is especially important, because the batter is beat pretty vigorously in the stand mixer to make it light and fluffy.

Even with all of that information, I ran into a problem. My cakes fell.

It’s not totally visible from this photo, but there was an obvious bowl in the top, which made things difficult when I started stacking and filling the layers. I did some reading into “why cakes fall,” and determined that I may have contributed to this fiasco. Cakes can fall for a number of chemistry related reasons including altitude adjustments for high elevation, old baking powder, low temperature, too much or too little sugar (sugar amount determines the temperature at which the batter sets), over or under beating the batter which incorporates too much or too little air, as well as opening the oven half way through the baking and excessive jarring of the batter in the pan before it sets. Oops. Let me explain. I had positioned the pans on separate racks – one above the other. When I checked (half way through) I noticed that the top cake was nicely browned while the bottom cake was still pasty white. I decided to switch the pans from top to bottom which probably burst some of the bubbles before the cake had set, causing them to fall into oblivion.

While the cakes were cooling, I whipped up the icing. This recipe is almost like a meringue with whipped egg whites. It included corn syrup to make it shiny, sugar, a splash of water, and egg whites. The concoction was heated to 160° F over a double boiler…

and then whipped into oblivion in the stand mixer.

Now for ASSEMBLY:

Since this was a four layer cake made from two cakes, each one needed to be horizontally divided. First of all, I didn’t have a long, serrated bread knife, so that was difficult but manageable. There’s something to be said for the right tools for the job. Second, and not so manageable, was the giant bowl in the middle of each cake, leading to a cake that would ultimately sink in the middle, rather than mound, and for some pretty thin layers in the middle. I started by cutting each of the two layers in half to create four layers. Then I began layering them, separated by the lemon curd.

Since some of the layers were less than sturdy (being approximately four grains of flour thick in the middle where they had fallen) I used a flat baking sheet to transfer and slide them onto the stack.

Assembly proceeded mostly without a hitch (this was actually spectacular since I’ve never actually assembled a layer cake) but it was a little off center and, frankly, looked like it had too much to drink. I frosted it with the icing and everything looked wonderful.

…for about two minutes. Then my icing started oozing and melting all over. It is really devastating to show my cake failures all over the internet, but it inspires me to learn what went wrong. Namely acid. After some reading, I discovered that egg whites are an alkaline pH and the proteins in them cause them to whip up so nicely. When egg whites are beaten, the protein coils unravel and begin to form bonds and networks. These networks form over the surfaces of air bubbles and keep them from popping. This is excellent, while it lasts. Over beating egg whites causes an overbonding of proteins and begins to create protein coagulation, and there is a very fine line between perfectly beaten and overbeaten. Overbeating causes coagulation which keeps the proteins from holding their network form and – thus – they can’t maintain the surface integrity over the air bubbles, so it begins to slump and deflate. The fix? Acid. Cream of tartar is highly recommended since it is the only solid acid, and it is flavorless. Vinegar and lemon juice work as well, but they have distinct flavors, and sometimes adding additional liquid to a meringue or icing is undesirable. The point of adding an acid is to broaden the margin in which the egg whites are “perfectly beaten” to “over beaten.” An acid increases the number of free hydrogen molecules, allowing more hydrogen bonds to be created. Hydrogen bonds are incredibly strong and help the egg whites to hold their stiff-peaked form.

Here is the lumpy, slouching form of my deflated icing and uneven cake

As you can see from the next photo, the layers were a little even. I tried adding additional lemon curd in the middle of the cake to even out the slumping middle, but I think it just became a gooey  mess

On a side note, I seriously thought I just lost my entire post and I almost had an aneurysm. Moving on.

Overall, the cake was delicious. I didn’t personally think the icing fit with flavor the the cake. It was almost cloyingly sweet and tasted like marshmallow. According to my husband, it tasted exactly like Fluff, which got high marks from him. I am considering adding lemon juice as an acid just to cut the sweetness a touch when I remake the recipe.

Overall, I learned quite a bit about the problems I encountered, and it was exciting to use my prior knowledge when I asked myself “why?” I hope y’all learned something today! I know I did.

This is actually the first time I’ve encountered any of these problems, so tell me: who has had problems with their cakes falling? did you discover how to fix it? Did your icing run all over the kitchen after you worked so hard on it? Please tell me, I’m dying to know that I’m not the only inept cook.

XOXO