The Science of Baking
Post on 04-Apr-2016
DESCRIPTIONThe science of baking Kitchen chemistry By Kelly Stewart
The science of bakingKitchen chemistryBy Kelly StewartApril 27, 2009
In the home kitchen, there are two kinds of people: cooks and bakers. For cooks, recipes are mere suggestions,flexible in their ingredients and proportions. For bakers, on the other hand, recipes are gospel truth, precise in theirmeasurements and techniques.
Me, Im definitely a cook. I enjoy the spontaneity of tweaking a recipe or making one up basedon whats in the fridge. But the downside to being a cook is that, no matter how often Iveprepared a particular bread or pastry recipe, I cant guarantee the same results every time. Ienvy my grandmother, who can whip together dough for dozens of dinner rolls without evenmeasuring the flour. She just knows when the dough looks and feels right.
After a recent cheese-puff disaster my typically lofty gougres came out of the oven as flat as cookies Idecided to become less of a cook and more of a baker. So I quizzed six baking experts about ingredients andtechniques.
The secret to successful baking? Its all in the chemistry. Andheres the scientific lowdown on how each basic bakingingredient functions in the kitchen.
I started my research with flour. After all, the protein in flourlends structure to baked goods, from poufy popovers to crustyartisanal breads. As pastry chef Shuna Fish Lydon wroterecently on her Eggbeater blog, In baking, protein providesthe walls holding up roofs. But you cant build walls of anykind without elbow grease.
I coaxed Peter Reinhart a baking instructor and the authorof several books, including The Bread Bakers Apprentice into sharing the basics behind dough construction. He told methat two proteins glutenin and gliadin inhabit flour.
When you add water to the flour to hydrate the ingredients, these proteins are drawn to each other and bond,Reinhart says. This new protein is gluten.
Reinhart suggested I call Shirley Corriher for the nitty-gritty on the science of baking. A former VanderbiltUniversity biochemist, Corriher turned her kitchen into a laboratory of sorts and published her experiments in twocookbooks, CookWise and BakeWise.
Kneading builds gluten networks, says Corriher, which in turn support bread. While dough rises, existing glutenthreads touch and create more links. Later, inside the oven, the proteins and starches in the flour transform into thesturdy webbing inside a loaf of bread.
Pastries, on the other hand, demand a more tender crumb. Corriher explains that the lower protein content inpastry, cake, and all-purpose flour creates a less rigid gluten network and a finer crumb.
Gougres (FrenchCheese Puffs)Dinner Rolls
Essential ingredients for baking, clockwise from top left: eggs,butter, milk, vegetable oil, baking powder, baking soda, salt, sugar,yeast, and flour.
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But selecting the right flour for the job isnt as easy as it seems. The problem with all-purpose flour is that it is allover the place in protein content, Corriher says.
So she shared a trick to help determine flours protein content: Measure two cups into a bowl and stir it with ascant cup of water.
If you have a high-protein flour, its going to suck in water like crazy andform a dough, she says. Less protein-rich flour wont come togetherunless you add more flour.
I tested the all-purpose white flour in my cupboard. Sure enough, I had made my top-heavy cheese puffs with ahigh-protein flour more appropriate for hearty bread.
Unfortunately, as Corriher says, theres no easy way to determine the protein content of flour. Just check out thelabel on the flour in your pantry. The manufacturer has rounded the protein weight to the nearest gram perquarter-cup. So one flour that contains 2.5 grams of protein per quarter-cup, and a second flour that contains 3.4grams, would both round to 3 grams of protein for labeling purposes. That difference, however slight, can affecthow the rest of the ingredients play off each other.
Because theres so much guesswork involved with flour and the other elements of baking, Reinhart suggeststreating recipes as templates, not rigid rules. But wait a sec; isnt precision the whole point of baking?
Every situation is different, he says. The instructions are a general guideline to get you into the ballpark. You letthe dough dictate to you what it needs.
Bakers benefit from learning more about the reactions that happen in their mixing bowls, pastry chef Carole Bloomadds. Once you know how ingredients work, thats when you can start to improvise, she says.
I love peering through the oven window to watch as loaves and cakes puff up. Yeast, baking soda, and bakingpowder combined with the extra oomph of steam supply airiness to bread and pastries.
Reinhart reminded me that yeast literally brings bread to life. As yeast feeds on sugars in dough, it oozes a liquidthat, when it touches an air pocket, lets loose carbon dioxide and alcohol. Or, in Reinharts words, The yeastburps and sweats. The elastic dough traps those tiny carbon-dioxide bubbles like a balloon.
Baking powder and baking soda, meanwhile, release carbon dioxide that only enlarges bubbles that are alreadyin the batter, Corriher explains.
Its important to cream butter thoroughly to whip those bubbles of CO2 into the fat. Start with butter thats soft, notrunny, advises Bloom, whose latest cookbook is Bite-Size Desserts. If the butter is too firm, youre not going toget it to that fluffy stage.
Baking soda reacts with acids citrus juice, buttermilk, molasses, honey, and chocolate are all acidic toproduce carbon dioxide, which in turn puffs the batter.
Double-acting baking powder, adds Corriher, releases carbon dioxide twice during the baking process: once whenit reacts with liquids during mixing, and again when its exposed to higher temperatures in the oven.
Bakers struggling with heavy cakes and too-dense breads can often point to leavening agents as the culprit. Resistthe temptation to add more leavener to compensate for a weak rise, warns Corriher: If the recipe is overleavened,the bubbles run together, float to the top, and pop and your pastry sinks.
One teaspoon of baking powder or just a quarter-teaspoon of baking soda is enough to leaven one cup offlour, says Corriher.
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In pastry, eggs help bind things together, explains Mani Niall, a pastry chef and the author of the cookbookSweet!.
Egg whites work as leavening agents. When heated, the proteins in egg whites uncoil and practically explode upthe sides of the pan, just like Dutch baby pancakes.
Corriher has experimented with substituting egg whites forwhole eggs to force a bigger rise out of cream puffs orgougres. But substitutions can be tricky, she cautions,because the proteins in egg whites force out moisture whentheyre heated. The result: puffy but chalk-dry pastries.
Egg yolks, on the other hand, lend richness and moisture tobaked goods, says David Lebovitz, a pastry chef whosebooks include Room for Dessert. If you were to make a cakewith all egg yolks, itd be moist, but also kind of wet, heexplains.
And make sure to bring eggs to room temperature beforemixing. If you add cold eggs to butter and sugar, they wontcombine correctly, Lebovitz warns.
As anyone whos ever eaten a delicate, buttery croissant can attest, fats are incredible tenderizers. Fats coat theproteins in flour, says Corriher, preventing them from bonding with water and forming gluten.
You dont want a lot of gluten in muffins and scones, making them chewy in a breadlike way, Niall says.
Oil coats flours proteins better than butter does, which explains why oil-based cakes are moister thanbutter-based cakes.
Sugar and milk
Sugar gives pastries their addictive sweetness, but it also helps keep them moist. If you think of baked goodswithout sugar, its bread, because its not tender, says Niall. Not surprisingly, theres a scientific explanation behindsugars tenderizing properties.
If you have a lot of sugar present, your glutenin runs off with sugar, your gliadin runs off with sugar, and you dontget much gluten formed, Corriher explains. And then your pastry wont have any structure.
Likewise, adding milk to batter helps keep baked goods moist. Milk contains the sugar lactose, which bonds withflour proteins and hinders gluten formation.
Both sugar and milk promote browning, Corriher says. Essentially, bread crust is caramelized sugar.
Recipes for baked goods usually call for a pinch of salt because it helps conceal bitter tastes. But the mineral alsoplays a key role in gluten formation, says Patti Christie, a biochemist who teaches a series of popular kitchen-chemistry courses at the Massachusetts Institute of Technology.
The reason you add salt to dough is to make dough more elastic, Christie explains. Charged amino acids in theflour are going to interact with the ions in the salt, and that helps line up the gluten fibers. Your bread is going tohave better texture.
As for sugary treats, a bit of salt added to batters and doughs helps to balance sweetness and enhance otherflavors during baking. And if added as a finishing touch to, say, chocolate-chip cookies, salt provides a pleasing
Because it calls for lots of eggs, a Dutch baby pancake puffs up inthe oven and then deflates once removed from the heat.
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After talking with bakers and chemists about ingredients, methods, and reactions, I decided there was one moreperson I needed to quiz: my grandmother, the master baker in my family. She didnt have advice about science,but she did say that practice is the key to good baking.
But just how much practice? Well, shes baked four to six dozen dinner rolls for our big, hungry family every weekor two for the past 58 years. That adds up to nearly 150,000 rolls in more than 2,000 baking sessions.
After youve made bread for a while, you can tell just by feeling the dough how good a batch youre going to get,she says.
So even though Im fresh out of my lessons on baking science, I still have lots of homework ahead of me. But withenough experimentation, I may be able to switch on my family baking genes after all.
Based in Portland, Oregon, Kelly Stewart is the editor of Roast magazine. Her writing about food has appeared inthe Christian Science Monitor, Meatpaper, and Zagat Survey guidebooks.
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