The Chemistry of Baking

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The following information is a place to converse about the Chemistry of Baking

Tentative Schedule

SOfIA 2016 Schedule

Chemistry Topics

  • SOfIA students: put this in the order that you will be presenting, and put the correct name with the topic.

Flour Types

  • Brandon

What is flour?

Flour is primarily composed of starch, the rest is fiber, water, and trace amounts of fat and minerals. It is most commonly made from wheat, because other grains aren't capable of producing sufficient amounts of gluten or they contain compounds that inhibit gluten formation. Flour plays a vital role in the chemical process of baking. Each kind of flour has its own special characteristics, which is why it's important to know which kind of flour will best suit your desired baked good. The biggest difference between the various kinds of flour lies in their protein content. This affects how the flours absorb water, for example: the same amount of water in a cake flour could lead to runny, more watery dough while it could lead to a more structured, firm dough with bread flour. Protein content also plays a large role in the development of gluten, which is responsible for the structure, rigidity, and texture of the intended product. Let's explore the differences between some common kinds of flour before we look at the reaction that occurs with flour while baking.

The Different Kinds of Flour

  • All-purpose flour: As its name suggests, this is easily the most versatile kind of flour on the market. Its average protein content varies by brand and ranges from 10-11.7%, so it produces enough gluten to give sandwich bread decent structure without being too wholesome. Bleached flour tends to be bland and flat in flavor.
  • Cake Flour: This has a lower protein content than the all-purpose flour and averages 6-8% and therefore has much less gluten than all-purpose, which accounts for its finer, delicate crumbs. Most are put through a bleaching process, which changes the starches in the flour so that it can absorb more water and fat. (1 cup of cake flour is equal to 2 tablespoons of corn starch and 7/8 cups of all-purpose flour.)
  • Bread flour: Bread flour has a relatively high protein content with averages from 12-14%. This results in a very high gluten development, giving artisanal/rustic breads their characteristic strong and chewy structure. This is often far too strong sandwich bread.
  • Whole-wheat flour: This is made from all 3 parts of the wheat kernel (INSERT LINK)- the endosperm, the fiber-rich bran, and the vitamin-packed germ. These make it more nutritious, flavorful, and dense. Breads baked with whole-wheat flour tend to be heavy, hearty, and sour-tasting.
  • Specialty Flours: There are a few specialty flours that the average chef will not encounter in their everyday lives and tend to be more useful to the professional bakers. These include:
  • Pastry Flour: This flour is often used for pastries and contains a protein content between the all-purpose flour and the cake flour.
  • Self-Rising Flour: This contains a leavener for convenience.

What's the big deal about flour?

Flour plays a crucial role in the reactions that occur when baking. All flours naturally contain both alpha and beta amylases, which are enzymes that break the starches in the dough down to fermentable sugars. These fermentable sugars are maltose and glucose. Scientists have looked at a way to bring the quality of slowly cultured starter dough to the fast doughs that many people use nowadays by enriching flours with more amylase enzymes. This expediates the process by breaking the starch down in less time, which means that there are more sugars available for yeast fermentation and a quicker production of carbon dioxide gas and ethanol, which gives dough its characteristic scent. As previously mentioned, protein content is responsible for each kind of flour's unique attributes. The two proteins that are important to gluten production are glutenin and gliadin. These proteins are hydrated when the flour is mixed with water, resulting in gluten formation. This is because these proteins are dominated by hydrophobic amino acids like glutamine, which has a strong tendency to form hydrogen bonds between protein strands. These hydrogen bonds are solely responsible for the structure and behavior of gluten. We see it as well-structure bread crumb from an artisanal loaf that you can get at a specialty bakery or the less-structured crumb of a cake or cupcake.

There are variations of gliadins (alpha, gamma, and omega gliadins) in flour that are responsible for the common gluten intolerance known as Celiac's disease, which are soluble in alcohols and connect through disulfide linkages. Glutenins are much larger proteins that account for ~47% of the total protein in wheat flour and is responsible for the elasticity and strength of the dough. (Think of glutenins as long strings that become stuck together in an elastic web through their interactions with gliadins.) This is an essential part of gluten formation because as the dough is worked more, the web of proteins increases in strength and durability. If the web of proteins is already strong and durable, then what is the significance of kneading the dough and working in the flour? This physically pushes the protein molecules together, which allows the disulfide bonds to form and stretch, aligning the gluten into long parallel sheets that allow for efficient trapping of air and hydration of gluten. The hydration of gluten introduces small pockets of water in between the layers of gluten that turn into steam and create the final rise of the dough. The reason why we knead the dough is to overcome the naturally slow reaction rate of gluten formation.

References

Cook's Illustrated "Baking Book: Baking Demystified With 450 Foolproof Recipes From America's Most Trusted Food Magazine"

The Royal Society of Chemistry "On the Rise" [1]

Water

Does water ion concentration have an effect of the baked good?

Sugar

  • Types of Sugar compounds
    • Lactose: a sugar present in milk, a disaccharide contain glucose and galactose units
    • Maltose: a sugar produced by the breakdown of starch by enzymes found in malt and saliva, a disaccharide consisting of two linked glucose units
    • Sucrose: a compound that is the chief component of cane or beet sugar
  • Roles Sugar Plays in Baking
    • Gluten Development: Sugar acts as a tenderizing agent by absorbing water and slowing gluten development
    • Leavening: Sugar increases the effectiveness of yeast by providing an immediate source of nourishment for growth
    • Creaming: Sugar helps promote lightness by incorporating air into the shortening
    • Egg Foams: Sugar serves as a whipping aid to stabilize beaten egg foams
    • Egg Protein Coagulation: Sugar molecules disperse among egg proteins and delay coagulation of the egg proteins during baking
    • Gelatinization: Sugar tenderizes by absorbing liquid and delaying gelatinization
    • Caramelization: Sugar caramelizes when heated above its melting point, adding flavor and leading to surface browning which improves moisture retention in baked products
    • Surface Cracking: Sugar helps produce the desirable surface cracking of some cookies because of the relatively high concentration of sugar and the low water content in cookies

http://www.sugar.org/images/docs/sugar-functional-roles.pdf

  • Maillard Reaction
    • The Maillard reaction is a chemical reaction between an amino acid and a reducing sugar, usually requiring the addition of heat.
    • This creates flavor and changes the color of food
      • The Maillard reaction is responsible for many colors and flavors in foodstuffs:
        • caramel made from milk and sugar
        • the browning of bread into toast
        • the color of beer, chocolate, coffee, and maple syrup
        • self-tanning products
        • the flavor of roast meat
        • the color of dried or condensed milk

http://web.mnstate.edu/provost/BCBT100%20Browning.pdf

Protein

What is a protein?

  • an organic compound that consists of several molecules
  • long chains of amino acids (polypeptides) that are found in all living organisms
  • help assist in muscle, hair, collagen growth and are enzymes and antibodies
  • made up of carbon, hydrogen, oxygen, nitrogen in a carboxyl group, amine group, and an "R" group that is interchangeable
  • connected by peptide bonds

What types of proteins are there?

  • monomeric proteins (single polypeptide chain)
  • oligomeric protein (many polypeptide chains)
  • simple proteins
    • composed of only amino acids
  • conjugated proteins
    • amino acids as well as other inorganic compounds (called prosthetic groups)
    • glycoproteins (carbohydrates)
    • lipoproteins (lipids)
    • nucleoproteins (nucleic acids)

Proteins from a chemist's view...

  • 20 different proteins made up of several different combinations of atoms
  • single carbon atom in the middle with the rest bonded
    • amine group (NH2)
    • carboxyl group (COOH)
    • R group (also called a side chain)
      Structure of an Amino Acid
  • elements in side chain/R group can determine special functions of protein
    • for example, making a single protein positively charged or negatively charged, basic or acidic, etc.

Why are proteins important in baking?

  • help provide different levels of structure in baked goods
    • eggs and flour give most protein content
  • remember Brandon's report of different flours from earlier
  • different kinds of flour have different amounts of protein, contributing to different densities and structures of breads, cakes, etc
    • cake flour (6-8% protein)
    • pastry flour (between protein % of cake and all-purpose flour)
    • all-purpose flour (10-11.7% protein)
    • bread flour (12-14% protein)
    • whole wheat flour which has all three parts of wheat kernel (bran, germ, endosperm) and are mixed with all purpose flour
  • heat and mixing break bonds of proteins, forcing them to rejoin bonds to other molecules
    • makes batter or dough thicker
  • gluten formed once water is added
    • gliadin and glutenin in flour turned into gluten

What are good dietary sources for proteins?

  • Seafood
  • White meat
  • Dairy products (milk, cheese, yogurt, etc.)
  • Eggs
  • Beans

What have I baked, and how do proteins affect it?

  • Portuguese Sweet Bread
    • recipe called for bread flour
      • best kind of flour for the recipe
      • 12-14% protein content, developing a lot of gluten
      • makes bread chewier and makes sure it won't fall apart easily
    • 2 large eggs helped add protein to batter
    • 6 tbs water helped glutenin and gliadin bind, creating the gluten
  • Rye-Flour Chocolate Chip Cookies
    • changed flour in experiment to see different densities and chewiness of cookies
    • different color, different chewiness
    • still liked by majority of people although appearance was much like an oatmeal cookie
  • Sugar Cookie Cupcakes
    • recipe called for all-purpose flour
    • most versatile flour
    • provides good structure for cakes that should have a medium crumb but not too chewy

Sources

Starch

Starch is a white, tasteless, grainy, condensation polysaccharide that is insoluble in cold water or other solvents and is produced by all green plants. Starch is manufactured in the green leaves during photosynthesis and serves the plant as a reserve food supply. In humans and other animals, starch is broken down into sugar molecules and then supply energy to the tissues.

Structure

Saccharide are molecular compounds made of three elements: Carbon, Hydrogen, and Oxygen. Monosaccharides are relatively small molecules, often called sugars. Monosaccharide have a general molecular formula (CH2O)n Where n can be 3, 5 or 6. Trioses, Pentoses, and Hexoses. Glucose is a Hexoses, making its chemical formula C6H12O6. Monosaccharides can undergo a series of condensation reactions, adding one unit after another until polysaccharides are formed. This is called condensation polysaccharide and the building blocks are called monomers. Starch exists in two forms: Amylose and Amylopectin. Both made from alpha glucose. Amylose makes up about 20% of starch and is an unbranched polymer and is more soluble in water than Amylopectin. Amylopectin makes up about 80% of starch and is branched.

Amylase is an enzyme that converts starch into simple sugars. There are two types if Amylase, Alpha and Beta, that differs in the way it attack the bonds of starch molecules. Alpha- amylase is found among living organism. An Alpha- amylase called Ptyalin is produced by the salivary glands and the pancreatic is secreted by the pancreas into the small intestine. Ptyalin is mixed with the food in your mouth and the process could last for several hours. As much as 30 or 40 percent of the starch you ingest can be broken down to maltase. The food passes to the small intestine and the remainder of the starch molecules are catalyzed mainly to maltese by pancreatic amylase. This occurs in the first section of the small intestine. The by product are ultimately broken down by other enzymes into molecules of gluclose, which are rapidly absorbed through the intestinal wall. Beta- Amylase can be found in yeast, molds, bacteria, and plants, practically in the seeds. Beta- Amylase attacks the straight chain of Amylose but is unable to break most of the branch chain in Amylopectin.

Starch Role In Baking Bread

Leaveners

Yeast-Rising to the Occasion

Yeast is an essential part of most baking processes. By breaking down the sugars provided by the mixture of flour and water, yeast begins to consume the sugar within the mixture, producing carbon dioxide (CO2) and alcohol in the process. When fresh bread dough is left proof, the CO2 gases build up within the dough, causing it to rise when left alone. However, a great deal of things are happening while the dough is proofing......

Along with aiding the bread dough to rise, yeast also helps to provide some structure to the bread. When water and flour are mixed together, the two proteins in the flour called glutenin and gliadin combine with the water to create gluten. This gluten (along with the yeast) is responsible for the strength and the structure of the bread. When dough is kneaded, the yeast inside is still active, releasing bursts of carbon dioxide. These bursts of gas move around more water and protein molecules, giving them a chance to form more gluten and create a more structured bread.

Along with aiding in the creation of a better gluten structure, the yeast in the dough also helps to create complex flavors within the bread. When the fermentation process starts within the bread, the yeast enzymes start breaking down starch into more flavorful sugars. At the beginning of fermentation, enzymes in the yeast start breaking down starch into more flavorful sugars. The yeast uses these sugars and sugars already present in the dough to produce carbon dioxide, alcohol, and a host of flavorful byproducts such as organic acids and amino acids. It is these acids that are responsible for the sour flavor in bread, specifically sourdough bread. The more enzymes present, the greater amount of reactions that break big molecule chains into smaller ones (amylose and maltose into glucose, proteins into amino acids), increasing the flavor.

As fermentation proceeds, the dough becomes more acidic. This is due in part to rising levels of carbon dioxide and the presence of more flavorful organic acids like acetic acid (vinegar) and lactic acid being formed from the alcohol in the dough. As a result of this acidity, more molecules in the break down. However, if more alcohol is formed, the yeast's activity will start to slow down.

Baking Soda and Baking Powder-Know the Difference

Baking soda and baking powder function like yeast by producing carbon dioxide gas in order to give baked goods their characteristic puffy texture. However, the similarities baking soda and baking powder tend to end there, since both perform two different reactions when put into your sweets.

  • Baking Soda-Let the Alkaline Live

Like yeast and baking powder, baking soda creates the carbon dioxide that lets cakes and cookies rise. However, the way this is done is very different to that of yeast. Rather than through fermentation, the alkaline in the baking soda combines with acidic ingredients (buttermilk, sour cream, etc...) to create the carbon dioxide; however, too much of a good thing can be dangerous. If too much leavener is added, the carbon dioxide bubbles will build up, collect, and burst, causing baked goods to become flat. Other than allowing pastries to rise, baking soda also promotes browning in foods, creating deeper, complex flavors. This tasty addition is a direct result of the Maillard (MAY-ard) reaction. The Maillard reaction is when carbohydrates and proteins are heated together and the sugar (from the carbohydrates) and the amino acids (from the proteins) combine to form hundreds of new, distinct flavor compounds. This reaction happens when an amino acid molecule is split apart, with acid end being acidic and the amino end being a an alkaline. When the alkaline end reacts with sugars, the browning process begins to occur. Even though baking soda isn't a natural leavener like yeast, it still causes some of our favorite desserts to rise and help improve the flavor as well.


  • Baking Powder-Two for the Price of One

Like yeast and baking soda, baking powder causes baked goods to rise due to the production of carbon dioxide. However, baking powder holds many traits that make it different from other leaveners, literally. Baking soda is a combination of baking soda and cream of tartar, a very acidic powder. When both of these are combined with cornstarch (to prevent the basic baking soda and acidic cream of tartar from mixing), they create baking powder. Since a moist, acidic environment is required for baking soda to produce carbon dioxide, baking powder is usually used as an ingredient used when the batter has no natural acidity. Another reason baking powder is unique is that it comes in two different forms: single-acting baking powder (which only has one acid combined with the baking soda—a quick-acting acid that begins to work when liquid is added to the batter) and double-acting baking powder (has two acids added to the baking soda, the second acid usually being sodium aluminum sulfate). While the single acting begins to work as soon as it's exposed to liquid, the double acting begins to work only when the dish is put in the oven, after the temperature has climbed above 120 degrees. In terms of which baking powder is the best, most people recommend using double-acting baking powder in all recipes. Baked goods rise higher since most of the rise with baking powder occurs at oven temperatures. Double-acting baking powder also provides sufficient lift in the oven to allow you to bake frozen (unbaked) dough. Single-acting baking powder, on the other hand, doesn't provide sufficient leavening for doughs with little liquid such as scones or muffin. With two unique formats and a unique way of activating, baking powder is an essential for any cook's kitchen.

Unorthodox Leaveners

Here are some other things that function like leaveners from KingArthurFlour.com:[2]

  • Air

The most basic leaven is simply the air that is captured in a dough or batter. This air is created and trapped by a number of different processes while dough is being mixed.

  • Beating and creaming

Don't minimize the importance of these steps; give them the time that's required. Electric mixers have greatly simplified the task of beating sugar, butter and eggs into a light and creamy emulsion for cake, or of making egg whites into meringue. When a recipe calls for 10 minutes of beating-do it!

  • Flour

Fluff up your flour before sprinkling it into a measuring cup. Aerated flour will get whatever you're baking off to a much lighter start. (One of the first things a King Arthur employee learns when taking our basic bread-baking class is to take a flour scoop and fluff up the first several inches of flour in its container.)

  • Fats

The way you incorporate fat into a dough or batter also increases the amount of air you add. Creaming butter and sugar together incorporates air, both through the action of the beaters, and because jagged sugar crystals "grab" air as they come to the surface. Vegetable oil will produce a heavier product because it just doesn't contain as much air as butter. Also, the water in butter, when heated in the oven, expands and turns to steam; this also helps create a lighter baked good.

  • Eggs

Most recipes calling for eggs have them beaten until they're light and lemon-colored; that's the signal that they've incorporated an appropriate amount of air. Egg whites can be beaten until they've ballooned with air and become meringue. And if you beat eggs together with fat (e.g., creaming eggs and butter), you produce an emulsion that can hold more air than either alone.

  • Liquids

Cool liquids have more oxygen than warm ones. We're not advocating cold necessarily, but use cooler (cool tap water, milk from the fridge) rather than warmer, unless directed otherwise.

  • Sweeteners

Dry sugars will capture more air in a batter or dough than liquid sweeteners. This isn't to say you shouldn't use honey or molasses or maple syrup; when liquid sweeteners are used, the recipe calls for another type of leavening to raise the batter sufficiently.

Sources

Baking Soda:[3]

Baking Powder:[4]

Yeast:[5]

Other Adjuncts

Gluten

  • Insoluble in water
  • Major goal with baking is learning to limit or increase for the best texture

General Gluten Information

  • Natural component in wheat, barley, rye
  • Proteins (gliadins and glutenins) combine with starch from endosperm of grain seed to form gluten
  • No true gluten in corn or rice (not good for bread baking)

Bread Making

  • Flour is mixed with water = starch dissolves and glutenin and gliadin molecules form
  • Kneading creates more connections among the molecules
  • Yeast creates CO2, making light dough
  • More water = more gluten connects
  • Gluten levels are different in different flours
  • Structure of yeast-raised doughs rely on gluten strongly

Celiac Disease

  • Cannot digest gluten - immune system sees gluten as a pathogen
  • About 1% of Americans

4 Steps to Limit Gluten

  • Start with the right flour
    • Bread flour - most proteins
    • pastry/cake flour - least proteins
    • All-purpose flour - good choice for almost anything
  • Beware of water
    • Water initiates the formation of gliadin and gluten
    • Flaky and tender - little water
    • Cakes and some bread doughs - lots of water
  • Handle with care
    • The more you mix, the stronger the connections of gluten become
    • Yeast doughs often require more kneading to smooth the strands, so the dough expands and rises with the production of carbon dioxide from the yeast
    • Biscuits and piecrusts are difficult because they require some gluten, but not as much as bread dough, therefore making overmixing easy
  • Understand how other ingredients affect gluten
    • Fats weaken gluten
    • Coat gluten proteins preventing the formation of strands
    • Shortening “shortens” gluten
    • Cutting in fats coats the flour resulting in less water absorbed
  • Sugar hinders gluten; salt helps it
    • Sugar attaches to water before the water can attach to glutenin and gliadin
    • Salt makes gluten sticky and strong

Sources

"'Taking Control of Gluten"':[6] "'Gluten"':[7]

Experiments

“The Chemistry of Baking” students have been familiarizing themselves with the fascinating chemical properties of basic baking ingredients. During the first week, students made bread dough from flour, water, yeast, and salt. Students have discussed the chemical components of flour, known as starch and proteins, which interact with water and yeast to form bread. However, there has been little discussion about the role of salt in making dough. Salt influences both the taste and structure of bread through its interactions with yeast and flour. To better understand the role of salt, SOfIA students were asked to read the following article from the Journal of Agriculture and Food Chemistry: “Disaggregation and Reaggregation of Gluten Proteins by Sodium Chloride.” (will put in link)


This article discusses the effect of the presence of NaCl in making dough, in regards to bread dough’s gluten constituents. The study uses a variety of different methods to discern the relationship of sodium chloride and gluten proteins, including a protein extraction and subsequent SDS-PAGE (sodium dodecyl sulfate… will talk about SDS page)

Students will be repeating the protein extraction and gel electrophoresis in the laboratory in order to draw their own conclusions about dough prepared with NaCl. They will follow the JAS study’s methods, with room for adjustments. Results and analysis of the experiment are TBA.

Recipes

Bread

Biscuits

Cookies

Cakes

Tarts

Stephanie and Brandon's Chocolate Pecan Tarts

Pie Crust Recipe:

  • 3/4 cup all-purpose flour
  • 1/2 stick unsalted butter, cold and diced
  • 1 tablespoon granulated sugar
  • 1 tablespoon milk

Directions: 1. In a food processor, add the flour, unsalted butter, and sugar. Pulse until it looks like fine sands. If not using a food processor, beat with a hand-held pastry cutter until mixture is fine. After, add in the milk and pulse until it forms a ball. 2. Transfer to a clean working surface and flatten a little. Roll out right away and cover with a plastic wrap. Store in the refrigerator before using.

Chocolate Pecan Filling:

  • 2/3 cup sugar
  • 1/3 cup margarine or butter, melted
  • 1 cup corn syrup
  • 1/2 teaspoon salt
  • 3 eggs
  • 1 cup pecan halves or broken pieces

Directions: 1. Beat sugar, margarine, corn syrup, salt and eggs with hand beater or electric mixer. Stir in pecans. 2. Line tart plates with the pie crust. Make sure uncooked crust is no more than an 1/8 inch thick. 3. Carefully pour 1/8 cup of chocolate pecan filling into each shaped tart. 4. Top with more crushed pecans, if desired. 5. Bake at 375 for approximately 15 minutes. 6. Let cool and enjoy! :)

Rachel & Z's Strawberry Jam Tarts

Tart Recipe:

  • 3 cups all purpose flour
  • 1 tbs sugar
  • 1 1/2 tsp kosher salt
  • 1 cup cold butter
  • 1/2 cup ice water
  • 1 large egg yolk
  • 1 tsp vinegar

Directions: Use a food processor to combine the flour, sugar, and salt in bowl. Cut the butter into small cubes about 1/2 inch thick. Add to flour mixture, until there is only pea-sized lumps left. Whisk together ice water, egg yolk, and vinegar in separate bowl. Pour liquid mixture into cut flour. Shape the dough into a ball. Pour the dough onto a floured surface and knead quickly and lightly. Divide the dough in half, wrap and refrigerate for at least 30 minutes.

Strawberry Jam:

  • 4 lbs strawberries
  • 2 lbs granny smith apples
  • 1/2 cup fresh lemon juice
  • 5 cups sugar

Directions: Wash, hull and cut the strawberries in half or quarters. Peel, core and chop the apples into smaller than 1/2 inch pieces. In an 8-quart pan, stir together the strawberries, apples, and lemon juice. Bring the mixture to a boil, stirring constantly. Add the sugar and stir until it is dissolved. Somewhat boil, stirring frequently, until the jam reaches 212 deg F (about 15-25 minutes).

Sam & Gabby's French Apple Pie Tarts

Tart Recipe:

  • 3/4 cup sugar
  • 1/4 cup all-purpose flour
  • 1 dash of salt
  • 2 tbs butter
  • 1 large egg yolk
  • 1/4 cup lemon juice

Directions: Pre-heat oven to 425. Mix dry ingredients together in one bowl. Once finished, add chilled butter to the mixture and use a pastry cutter to mix the butter in until it is the size of small rice grains. Make a hole in the dry ingredients to put the egg and lemon juice into. Knead together and divide dough into two. Roll into dough balls and wrap both with cling wrap. Let sit in the refrigerator for 30 minutes to chill.

French Apple Pie Crumble:

  • 1 cup all-purpose flour
  • 1/2 cup chilled butter
  • 1/2 cup brown sugar
  • 5 cups thinly sliced granny smith apples
  • 1 cup thinly sliced honey crisp apples
  • 1/2 tsp ground cinnamon

Directions: Mix sugar, flour, cinnamon, and salt together in one bowl and then add the bowl of cut up apples. Microwave tart insides inside a microwave for 5 minutes until soft. Fill tart pan with cut out tart bottoms. Use a mason jar lid to cut the pastries after they've been rolled out 1/8 of an inch thickness. Fill tarts with apple pie filling. Use the crumble and sprinkle over filled tarts by using a tablespoon of crust mixture. Stick in oven for 15-20 minutes or until browned.

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