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 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 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 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 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.
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.
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.