At our 2013 Science of Pie event, Christina Tosi, Zoe Nathan, and the fantastic students from the Science & Food undergraduate course taught us all about pies, baking, creativity, and the scientific process. We just can’t get enough pie science, so here are 5 fun facts related to baking and some of our favorite baking ingredients:
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The Science of Pie
Featuring Christina Tosi & Zoe Nathan
May 19, 2013
At the world’s first scientific bakeoff, the students of the Science & Food undergraduate course presented results from their final projects, including a live taste test of apple pies. The final projects were judged by Chefs Christina Tosi and Zoe Nathan, food critics Jonathan Gold and Evan Kleiman, and UCLA Professors Andrea Kasko, and Sally Krasne.
Christina Tosi on…
…creating cereal milk
“Cereal milk, fortunately for us but unfortunately for the scientific process, was very simple to make . . . But a lot of the other things that we make at Milk Bar go through a much more vigorous question asking and testing process before we actually decide whether or not its successful.”
…crack pie and re-inventing pie crust
“Crack pie is our approach to pie. It very much embodies our approach to pie. We don’t use a traditional American pie crust . . . Pie crust is an opportunity to surprise and wow and provide texture and flavor that is beyond, perhaps, you standard traditional American pie crust.”
…creativity, curiosity, and the scientific process
Whether or not we’re aware of it, the scientific process is often an integral part of cooking and baking. When Christina Tosi describes her creative process at Milk Bar, she might as well be describing the process of scientific research and discovery:
“The second that I got out of school and I was able to have my own voice, I stepped back and I looked at everything that I was taught and listened to and followed without questioning, and I questioned it. And not in a disrespectful way, just in a ‘Well, what if? Why and what if?’ And I think that that curiosity and that forcing yourself to question every single thing in the creative process is incredibly helpful … you really just need that wandering spirit and the courage to ask ‘Why?’ And then of course the momentum and the patience to test through and be willing to fail but also be excited when you succeed.”
Zoe Nathan on…
…being a traditional baker and working with simple ingredients
“A really good baker isn’t bored of flour, and isn’t bored of sugar, and isn’t bored of salt, and isn’t bored of butter. They just know that through process they can make an entirely different thing every single day using five ingredients.”
…how to create the most amazing pie
“My second biggest pet peeve as a baker is how people bake. They forget that this is also an ingredient. Color is flavor: without it, you don’t have flavor. It just doesn’t work. Color and baking time and how your pie looks needs to be treated as another ingredient. It’s just as important as salt, sugar, flour, or anything. If you forget your color, you didn’t make the thing. . . It’s like you don’t have chocolate for your chocolate chip cookies.”
…baking and being present
“I would wish for everybody to throw away their timers and to start to engage all of their senses. Smell! Is it done? Look at it! Is it ready? . . . The whole thing about baking is that it makes you be present.”
Continuing our Science of Pie adventure, we’ve invited Elsbeth Sites of Team Chia to share her pie science project, which examines the use of a very unconventional thickener to tune the viscosity of pie filling. Elsbeth is an undergraduate student of physiological sciences at UCLA who is passionate about food and writing, especially writing about food.
Have you ever baked a lovely pie, sliced it and placed it gently on your best dessert plates, then watched in despair as the filling fled its warm crust and bled all over the dish? This common and unfortunate experience led our team to investigate the viscosity of pie filling. We hoped to discover a way to produce a pie of perfect viscosity that upon slicing, would not spread over the plate too far, nor be too gelatinous. Most pies contain cornstarch to thicken their fillings. To make our project unique and to put a modern and healthy twist on our pie, we replaced starch with the trendy new superfood: chia seeds.
The outside of the chia seed contains large fibrous molecules called polysaccharides. When the seed is wet, these molecules are exuded from the seed and trap liquid. This allows the seed to hold approximately nine times its own weight in water, causing a bead of gel to form around the seed .
|Chia seed hydration. Chia seeds can absorb approximately nine times their weight in water. Water absorption creates a mucilaginous gel around the seed. Figures are from .|
With this knowledge of the chia seed, we posed these questions:
- How do we create a pie that does not bleed across a plate when sliced while not being overly gelatinous?
- Can chia seeds be used to increase the viscosity of our pie filling?
- At what concentration should the seeds be added to the pie to get an ideal viscosity without compromising taste or texture?
We defined our perfect filling to be one that spread slightly when placed on a flat surface without remaining too gelatinous and not spreading at all. A traditional apple pie filling prepared with cornstarch spread 5.6 centimeters in 60 seconds. Finding the right concentration of seeds to add was a tedious process, and the heat at which the pie was baked and served greatly affected the pie’s viscosity. As shown in the figure above, our control filling with no thickening agent spread on average 5.9 centimeters in 60 seconds—clearly too runny. The filling to which we added 0.5 teaspoons of chia seeds spread 5.5 centimeters. By evaluating these spread distances and tasting each filling, we agreed that the filling with only 0.5 teaspoons seeds yielded the best viscosity and palatability. Using more seeds than this overpowered the spices in the filling, making the pie taste nutty and giving it a slimy mouthfeel.
Our experiment was successful in that we answered our original questions:
- Chia seeds can indeed be used to tune the viscosity of apple pie filling.
- To produce an apple pie of optimal viscosity, replace cornstarch with 0.5 tsp chia seeds per ½ cup of filling. While our pie might appeal to the culinarily curious or health savvy, those who prefer a classic pie may find the seeds of the pie annoying, or might miss the texture that more traditional thickeners like cornstarch or flour provide the filling.
If a seedy apple pie up your alley, here is Team Chia’s recipe for Chia Seed Apple Pie. The truly adventurous might even try using chia seeds in a berry pie where thickening agents are more crucial and tiny seeds are less noticeable. If you do try another variation of a chia seed pie at home, let us know how it goes in the comments below!
Adapted from Everyday Food: Our Best Pie Crust
2 1/2 cups all-purpose flour, plus more for rolling dough
1 tsp salt
1 tsp sugar
16 tbsp (2 sticks) cold unsalted butter, cut into pieces
4 tbsp ice water, plus 2 more if needed
In a food processor, pulse flour, salt, and sugar several times to combine. Add butter. Pulse until mixture resembles coarse meal, with just a few pea-size pieces remaining.
Sprinkle with 4 tablespoons ice water. Pulse until dough is crumbly but holds together when squeezed with fingers (if needed, add up to 2 tablespoons more ice water, 1 tablespoon at a time). Do not over-process.
Turn dough out onto a work surface; form dough into two 3/4-inch-thick disks. Wrap both separately and tightly in plastic, and refrigerate until firm, at least 1 hour.
Pie Filling and Assembly
5 Granny Smith apples, sliced
3/4 cup granulated sugar
2 1/2 tsp chia seeds
1/2 tsp ground cinnamon
1/8 tsp ground nutmeg
1/2 cup cold water
3/4 cup apple juice
Preheat oven to 350 degrees.
Wash, peel, and core apples. Cut apples into 1/4- to 1/2-inch slices and place in cold water.
Combine sugar, chia seeds, and spices in a large pot with water and apple juice. Stir and cook on medium high heat until mixture thickens and begins to bubble. Boil for 1 minute, stirring constantly. Fold in apple slices immediately and remove from heat.
To assemble pie, roll dough into 2 14-insh rounds. Fit the first crust into the bottom of a 9-inch pie plate. Spoon filling into the pie dish. Cover the pie with the second crust, trimming the overhang to about 1 inch. Press upper and lower crust edges together and flute as desired. Cut steam slits in the center of the top crust.
Bake for 20 minutes at 350 degrees or until crust is golden brown.
- Muñoz LA, Cobos A, Diaz O, Aguilera JM (2012) Chia seeds: Microstructure, mucilage extraction and hydration. J Food Eng 108: 216–224. doi:10.1016/j.jfoodeng.2011.06.037.
On foraging for local ingredients in your college dormitory…
Our Judge’s Favorite winner of the 2013 Science of Pie event showed how beer and vodka affect pie crust color and texture. But they weren’t the only students who experimented with alcohol in their pies. Two other teams—Team Super Rum and the Beam Team—also used alcohol to create flaky, tender crusts. The Beam Team even added Kentucky bourbon whiskey (Jim Beam, of course) to their pie filling for an extra punch of flavor.
So why all the alcohol? According to the Beam Team:
“Our group was inspired by Alex Atala’s process of going out into the Amazon Forest and finding local plants to use as ingredients. As college students, we decided that our ‘native’ ingredient is alcohol since it is easily found in abundant quantities all around us, so we used our two favorite types of hard alcohol: whiskey and vodka.”
There’s another (more scientific) reason for boozing up a pie crust: alcohol creates a more tender, flaky crust than can be easily achieved with water alone. This happens because alcohol and water have very different effects on the formation of springy gluten networks in pie dough.
Gluten develops when two wheat proteins in flour, glutenin and gliadin, are mixed with water. Because parts of these proteins do not like to interact with water, the proteins begin to stick to each other much in the same way oil droplets come together when suspended in water. As a flour-water dough is mixed, the glutenin and gliadin molecules interact to form an extensive elastic network .
|Gluten development during dough formation. Scanning electron micrographs of gluten networks during early (A), middle (B), and late (C) stages of dough mixing . The development of these gluten networks requires water.|
While gluten networks are great for chewy bread dough, they are less than ideal for flaky, tender pie crust. An ideal pie dough has as just enough gluten to hold everything in the dough together. And while gluten development can be minimized by adding only scant amounts of water and handling the dough as little as possible, this is easier said than done.
A more practical solution is to replace some of the water with a liquid that does not promote gluten formation. Unlike water, alcohol inhibits gluten formation. By interacting with the gluten proteins, alcohol molecules limit their ability to stick to each other and form springy networks . Using alcohol in the place of water allows more liquid to be added to the dough while still restricting gluten formation. This results in a softer, more pliable dough that becomes tender and flaky when baked.
Like the recipe below, the Beam Team paired a vodka pie crust with a decadent bourbon and apple filling. Although vodka is typically used for its subtle flavor, any type of alcohol will prevent gluten formation. As their name suggests, Team Super Rum used rum instead of vodka to create a flaky and uniquely flavored crust. And we bet there are many more delicious possibilities in the realm of alcohol-based pie crusts. If you try this recipe with something other than vodka, share your new pie crust concoction with us in the comments below!
Foolproof Vodka Pie Crust
Cook’s Illustrated, November 2007
2 1/2 cups (12 1/2 ounces) unbleached all-purpose flour
1 tsp table salt
2 tbsp sugar
12 tbsp (1 1/2 sticks) cold unsalted butter, cut into 1/4-inch slices
1/2 cup cold vegetable shortening, cut into 4 pieces
1/4 cup cold vodka
1/4 cup cold water
Process 1 1/2 cups flour, salt, and sugar in a food processor until combined, about 2 one-second pulses. Add butter and shortening and process until homogeneous dough just starts to collect in uneven clumps, about 15 seconds (dough will resemble cottage cheese curds and there should be no uncoated flour). Scrape bowl with rubber spatula and redistribute dough evenly around processor blade. Add remaining cup flour and pulse until mixture is evenly distributed around bowl and mass of dough has been broken up, 4 to 6 quick pulses. Empty mixture into medium bowl.
Sprinkle vodka and water over mixture. With rubber spatula, use folding motion to mix, pressing down on dough until dough is slightly tacky and sticks together. Divide dough into two even balls and flatten each into 4-inch disk. Wrap each in plastic wrap and refrigerate at least 45 minutes or up to 2 days.
Bourbon Apple Pie Filling
2 tbsp all-purpose flour
6 or 7 apples, mix of tart and sweet
1/3 cup sugar
1/2 tsp cinnamon
1/2 tsp nutmeg
1/4 tsp salt
1/2 cup bourbon whiskey
2 tbsp lemon juice
2 tbsp butter cut into small pieces
Preheat oven to 425. Place bottom crust in pie plate.
Peel, core, and halve the apples. Cut into 1/4-inch thick slices, about 7 or 8 cups.
In a 4 quart saucepan, whisk together sugar, flour, cinnamon, nutmeg, and salt. Whisk in bourbon whiskey and lemon juice until evenly blended. Cook over medium heat, whisking frequently until the mixture boils and thickens slightly. Add apples and stir until evenly coated. Continue cooking, stirring continuously, for 3 minutes. Set aside to cool, stirring once or twice for 20 minutes.
Pour apple mixture into the pie shell, mounding apples slightly in the center. Dot with butter and add the top crust. Cut several steam vents into top crust.
Bake 25 minutes at 425. Reduce temperature to 350 and bake 45 minutes longer or until crust is brown and juices are bubbling.
Serve warm or chilled with whipped cream or ice cream.
- Pie crust recipe from Cook’s Illustrated via Serious Eats
- Bourbon apple pie filling recipe adapted from Group Recipes
- Technology of breadmaking (2007). 2nd ed. New York: Springer. 397 p.
- Amend T (1995) The mechanism of dough forming: Efforts in the field of molecular structure. Getreide Mehl Brot 49: 359–362.
Amy Rowat dissects the science of pie for the New York Times, while Harold McGee explains how vodka makes a light, crispy batter for frying fish. Apparently pie crust isn’t the only dough that benefits from a little alcohol! Read more
It’s summer. Berries and stone fruits abound, and so the season of pies continues. And we continue to think deeply about the science of pie. There has been intense interest in pies these past few months: first at the Science of Pie event; next at the World Science Festival’s Scientific Kitchen workshop at Pie Corps in New York; and most recently the New York Times Pie Issue. But we believe you can never know too much about pie. Here are 10 more things we think you should know…
1. A bit of high school chemistry goes a long way when baking pies.
The ideal gas law (PV=nRT) tells us that the volume of an air pocket gets bigger with increasing temperature. In the oven, molecules get more energy and start moving faster and faster, causing air pockets to get bigger and bigger; this can result in an inflated pie that collapses once you cut into it. At the same time, apples lose water, most of which gets converted to steam. Consider that a water molecule takes up about 1700 times more volume in the gas phase than in the liquid phase: if your crust were completely impermeable to water and all the steam got trapped inside, your pie would become much larger than your oven! Luckily much of that steam can escape through the crust and through steam vents. (This is also a good reason to be sure to avoid air pockets when you lay your crust into your pie tin!)
2. There is an art to cutting your fruit for a pie filling.
The way you cut your fruit is important. Smaller pieces of fruit will cook more quickly, but they also tend to lose more liquid since they have a higher surface-area-to-volume ratio. The geometry of your fruit pieces is also important for packing the filling into your pie. After placing your fruit slices into the center of the pie, pat them down to make sure they all like flat. This will create a pie with a lovely cross-section of layered fruits and, more importantly, will help to avoid air pockets that can expand in the oven.
3. Sometimes the best pie is a day-old pie.
Temperature is important for pie texture. Eating your pie the day after you bake it allows plenty of time for the pie to cool down and the filling to “set”. Because molecules flow more quickly past each other at higher temperatures, hot pie filling straight from the oven will be more runny; as the pie filling cools, starchy molecules like cornstarch and flour spend more time interacting with each other. As the pie cools, the pectin molecules of your fruit also spend more time interacting with each other. This results in a more solid, gel-like filling that will take longer to seep out of the pie when it is cut and served on a plate.
4. Think of butter as a gas.
Butter is really just a bunch of teeny tiny water droplets dispersed in a matrix of fat. In the oven, these water droplets convert from liquid to gas. This means that the chunks of butter you can see in your dough are really just big pockets of air waiting to happen. More air = flakier crust! While butters with the highest butterfat content are generally synonymous with the highest quality butter, when it comes to baking pie a slightly lower fat content, and higher water content, may be a good thing.
5. Wash with egg for a darker, more delicious pie crust.
All those lovely color and flavor molecules in a nicely browned pie crust are the result of the Maillard reaction, a chemical reaction that occurs between amino acids, which comprise proteins, and sugar molecules like lactose or glucose. Brushing an egg (protein) on your pie crust before baking is a great way to add extra color and flavor. For extra browning, mix some heavy cream into your egg wash (more protein plus lots of lactose).
6. Turn up the heat!
Maillard reactions happen faster at higher temperatures. Keep your oven hot (375F or so) to brown your pie that extra bit more. Another strategy is to start off at 400F, then turn down the temperature to 350F.
7. Bake your pie in parts.
A major challenge in baking pie comes from its complexity: you’ve got a crust that should be brown and crisp together with a filling that largely contains water. When contending with fruit pie fillings, one strategy is to prebake the bottom crust to help prevent it from becoming soggy. In this process of “blind baking,” don’t forget to prick holes in the bottom of your crust so the water vapor can escape. Filling your pie crust with pie weights or dried beans during this process can also help prevent layers of your wanton bottom crust from puffing up. Pie master Bill Yosses suggests taking this sequential baking process an extra step further: after the bottom crust has baked, it can be stitched into the sides of a crust using extra dough to “glue” the bottom to the sides. In the spirit of experimentation, this could be an interesting new method to try.
8. Create a pie crust with your “perfect” texture.
Typical attributes of a “perfect” pie crust include: flaky, tender, brown, and a little crispy. While the optimal texture of a pie crust is a deeply subjective and personal matter, here is a rough guide to how you can tune your pie crust texture simply by considering how you work your fat into your flour. For taste, color, and texture, we prefer butter, but shortening or lard can also be used.
- You want your fat to be solid when working it into the flour. Remember those little chunks of fat will become pockets of air in your crust! In a liquid form, it would coat the flour too evenly, resulting in a less flaky crust.
- Because butter melts around 30–32 degrees Celsius (86–90F), it can be tricky to make sure it remains solid while you work it with your hands (about 35 degrees Celsius or 95F). Prior to making your dough, cut your butter into small 1 x 1 cm cubes and place in the freezer for about 10-15 minutes.
- For a crust that has more form and larger flaky holes, work your very cold butter into the flour until you have a distribution of butter pieces with various sizes: some should appear the size of peas, others the size of almonds. When you work your butter in to achieve these sizes of chunks, much of the butter will get worked in so the rest of the dough will appear as coarse wet sand.
- For a tender and flaky crust you need a decent coating of fat around your flour. To achieve this, try the two-step method: (i) Divide your butter in half: cut one half into small cubes, and keep the remaining half in stick form. Place both halves in the freezer to ensure they are very cold. (ii) Work the stick of very cold butter into your flour by grating it in with a coarse grater. Work in thoroughly with your hands until the mixture has the texture of a coarse sand. (iii) Add the remaining half of your butter in cubes and work in with your hands until the largest pieces are about the size of peas. The theory here is that completely coating the flour in oil helps create a more “tender” crust.
- If you want to avoid getting your hands messy, or want to minimize heating of your butter, use a pastry cutter, or two knives held side by side, to work the butter into your flour.
9. Different types of flour create different types of pie crust.
What flour is the best flour for pie crust? This is a contentious question that has a variety of answers depending on personal preference, but the type of flour you use can have a major effect on the final texture of your crust. The protein content of flour, based on the type of wheat the flour was made from, will affect the extent of gluten formation in your dough. While springy networks of gluten proteins are great for chewy breads (bread flour has particularly high protein content), they can make pie crust dense and tough. Flours with lower protein content, such as pastry flour or cake flour, will create less extensive gluten networks and can produce a more tender crust. However, the pie crust ultimately needs to be formed into a dough, which can make it a challenge to work with a fragile dough that can result when using a low-protein content flour.
10. Almond extract tastes great in a fruit pie.
What more can we say? Nuts and fruit taste great together! A bit of almond extract is a delicious complement to apples and apricots alike.
On Sunday we held our third and final 2013 Science and Food public lecture: The Science of Pie. Renowned pastry chef Christina Tosi joined us all the way from New York to explain her process for creating new desserts, and Los Angeles native and super-star baker Zoe Nathan shared her tips for baking the perfect apple pie. Guests indulged in delicious goodies from Zoe Nathan’s Huckleberry Café, Compost Cookies from Momofuku Milk Bar, and espresso brewed by four talented baristas.
And, of course, there was pie.
For weeks, students from the UCLA Science and Food course have been studying the apple pie and using scientific inquiry and experimentation to try to create the “ultimate” apple pie experience. Students examined everything from how different apple varieties behave in pie filling to how the size and shape of the pie affects baking. Several students also played with unconventional ingredients, including avocado oil, yogurt, chia seeds, and whiskey.
The students presented their research projects and pies at Sunday’s event. While the public enjoyed sampling the scientific treats, the pies were scrutinized by an esteemed panel of judges made up of chefs (Christina Tosi and Zoe Nathan), food critics (Evan Kleiman and Jonathan Gold), and scientists (UCLA Professors Andrea Kasko and Sally Krasne). After tasting the pies a talking with the students, the public voted for their favorite pie and the judges settled on three additional stand-outs. The lucky winners all took home wonderful prizes from our friends at Breville.
Best Overall Pie
Alia Welsh (Team Sablé)
Apple pie with shortbread crust and streusel topping.
This solo effort explored the vast parameter space of pie, studying the effect of fat content and temperature on the texture of the shortbread crust, as well as the effect of pH on the browning of the streusel topping. The final winning pie had shortbread made with room temperature standard American butter.
Best Tasting Pie
Stephan Phan, Kevin Yang, Amirari Diego (Team Apples to Apples)
Deconstructed apple pie with pie crust crumbs and spherified apples.
Using the technique of spherification, this team applied their knowledge of diffusion and gelation to prepare “reconstituted” apples. They found that optimizing both the calcium chloride concentration and gelation time was key to making a delicious modernist apple pie.
Judge’s Favorite Pie
Qiaoyi Wu, Qinqin Chen, Michelle Cheng (Team Aπ3)
Pie crust made with different liquids, including vodka, beer, and sparkling water.
Seeking to perfect pie crust texture, team Aπ3 experimented with different liquids that may impede the formation of gluten protein networks. Gluten gives structure and stability to pie dough, but can also make pie dough dense and tough when over-developed. The team examined the porousness, density, and browning of pie crusts prepared with three different liquids compared to water and concluded that vodka creates the flakiest pie crust.
People’s Choice Award
Elan Kramer, Caleb Turner (Team “Insert Team Name Here”)
Frozen apple pie with peanut butter mousse.
This student duo thought outside the box with this creative apple and peanut butter pie. To create the ultimate peanut butter experience, the team experimented with the effect of egg white content on the texture and density of the peanut butter mousse.
The Science of Pie was the perfect end to a fantastic lecture series. We are so grateful to our amazing lecturers and all the people and sponsors who made the lectures possible. And although the 2014 lectures might seem impossibly far away, don’t worry—the Science & Food blog is not going anywhere! Keep an eye on out for more exciting food science posts, profiles, recipes, and maybe even a few videos through the rest of the year.