The chemistry of cookies - Stephanie Warren
-
0:07 - 0:11In a time-lapse video,
it looks like a monster coming alive. -
0:11 - 0:14For a moment, it sits there innocuously.
-
0:14 - 0:16Then, ripples move across its surface.
-
0:16 - 0:20It bulges outwards,
bursting with weird boils. -
0:20 - 0:21It triples in volume.
-
0:21 - 0:25Its color darkens ominously,
and its surface hardens -
0:25 - 0:29into an alien topography
of peaks and craters. -
0:29 - 0:31Then, the kitchen timer dings.
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0:31 - 0:32Your cookie is ready.
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0:32 - 0:34What happened inside that oven?
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0:34 - 0:36Don't let the apron deceive you!
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0:36 - 0:38Bakers are mad scientists.
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0:38 - 0:40When you slide the pan into the oven,
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0:40 - 0:43you're setting off a series
of chemical reactions -
0:43 - 0:47that transform one substance, dough,
into another, cookies. -
0:47 - 0:50When the dough reaches
92 degrees Fahrenheit, -
0:50 - 0:52the butter inside melts,
-
0:52 - 0:54causing the dough to start spreading out.
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0:54 - 0:56Butter is an emulsion,
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0:56 - 0:57or mixture of two substances
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0:57 - 0:59that don't want to stay together,
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0:59 - 1:01in this case, water and fat,
-
1:01 - 1:04along with some dairy solids
that help hold them together. -
1:04 - 1:07As the butter melts,
its trapped water is released. -
1:07 - 1:11And as the cookie gets hotter,
the water expands into steam. -
1:11 - 1:13It pushes against the dough
from the inside, -
1:13 - 1:16trying to escape through the cookie walls
-
1:16 - 1:18like Ridley Scott's chest-bursting alien.
-
1:19 - 1:22Your eggs may have been home
to squirming salmonella bacteria. -
1:22 - 1:27An estimated 142,000 Americans
are infected this way each year. -
1:27 - 1:30Though salmonella can live for weeks
outside a living body -
1:30 - 1:32and even survive freezing,
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1:32 - 1:35136 degrees is too hot for them.
-
1:35 - 1:38When your dough reaches
that temperature, they die off. -
1:38 - 1:41You'll live to test your fate
with a bite of raw dough -
1:41 - 1:43you sneak from your next batch.
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1:44 - 1:47At 144 degrees,
changes begin in the proteins, -
1:47 - 1:49which come mostly
from the eggs in your dough. -
1:50 - 1:52Eggs are composed of dozens
of different kinds of proteins, -
1:52 - 1:55each sensitive to a different temperature.
-
1:55 - 1:57In an egg fresh from the hen,
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1:57 - 2:00these proteins look
like coiled up balls of string. -
2:00 - 2:02When they're exposed to heat energy,
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2:02 - 2:06the protein strings unfold
and get tangled up with their neighbors. -
2:06 - 2:07This linked structure
-
2:07 - 2:09makes the runny egg nearly solid,
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2:09 - 2:12giving substance to squishy dough.
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2:12 - 2:15Water boils away at 212 degrees,
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2:15 - 2:16so like mud baking in the sun,
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2:16 - 2:19your cookie gets dried out
and it stiffens. -
2:19 - 2:21Cracks spread across its surface.
-
2:21 - 2:24The steam that was bubbling
inside evaporates, -
2:24 - 2:28leaving behind airy pockets
that make the cookie light and flaky. -
2:28 - 2:30Helping this along
is your leavening agent, -
2:30 - 2:31sodium bicarbonate,
-
2:31 - 2:33or baking soda.
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2:33 - 2:36The sodium bicarbonate reacts
with acids in the dough -
2:36 - 2:40to create carbon dioxide gas,
which makes airy pockets in your cookie. -
2:40 - 2:43Now, it's nearly ready
for a refreshing dunk -
2:43 - 2:45in a cool glass of milk.
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2:45 - 2:47One of science's tastiest reactions
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2:48 - 2:50occurs at 310 degrees.
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2:50 - 2:52This is the temperature
for Maillard reactions. -
2:53 - 2:54Maillard reactions result
-
2:54 - 2:58when proteins and sugars break down
and rearrange themselves, -
2:58 - 2:59forming ring-like structures,
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2:59 - 3:01which reflect light in a way
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3:01 - 3:03that gives foods like Thanksgiving turkey
-
3:03 - 3:04and hamburgers
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3:04 - 3:06their distinctive, rich brown color.
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3:07 - 3:08As this reaction occurs,
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3:08 - 3:11it produces a range of flavor
and aroma compounds, -
3:11 - 3:13which also react with each other,
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3:13 - 3:16forming even more complex
tastes and smells. -
3:17 - 3:18Caramelization is the last reaction
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3:18 - 3:20to take place inside your cookie.
-
3:20 - 3:22Caramelization is what happens
-
3:22 - 3:26when sugar molecules
break down under high heat, -
3:26 - 3:28forming the sweet, nutty,
-
3:28 - 3:32and slightly bitter flavor compounds
that define, well, caramel. -
3:32 - 3:36And, in fact, if your recipe
calls for a 350 degree oven, -
3:36 - 3:37it'll never happen,
-
3:37 - 3:41since caramelization
starts at 356 degrees. -
3:41 - 3:43If your ideal cookie is barely browned,
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3:43 - 3:46like a Northeasterner on a beach vacation,
-
3:46 - 3:48you could have set
your oven to 310 degrees. -
3:49 - 3:51If you like your cookies
to have a nice tan, -
3:51 - 3:52crank up the heat.
-
3:52 - 3:56Caramelization continues
up to 390 degrees. -
3:56 - 3:57And here's another trick:
-
3:57 - 3:59you don't need that kitchen timer;
-
3:59 - 4:02your nose is a sensitive
scientific instrument. -
4:02 - 4:04When you smell the nutty, toasty aromas
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4:04 - 4:07of the Maillard reaction
and caramelization, -
4:07 - 4:08your cookies are ready.
-
4:08 - 4:10Grab your glass of milk,
-
4:10 - 4:11put your feet up,
-
4:11 - 4:15and reflect that science
can be pretty sweet.
- Title:
- The chemistry of cookies - Stephanie Warren
- Speaker:
- Stephanie Warren
- Description:
-
View full lesson: http://ed.ted.com/lessons/the-chemistry-of-cookies-stephanie-warren
You stick cookie dough into an oven, and magically, you get a plate of warm, gooey cookies. Except it's not magic; it's science. Stephanie Warren explains via basic chemistry principles how the dough spreads out, at what temperature we can kill salmonella, and why that intoxicating smell wafting from your oven indicates that the cookies are ready for eating.
Lesson by Stephanie Warren, animation by Augenblick Studios.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 04:30
Krystian Aparta edited English subtitles for The chemistry of cookies | ||
Krystian Aparta commented on English subtitles for The chemistry of cookies | ||
TED edited English subtitles for The chemistry of cookies | ||
Jessica Ruby approved English subtitles for The chemistry of cookies | ||
Jessica Ruby accepted English subtitles for The chemistry of cookies | ||
Jessica Ruby edited English subtitles for The chemistry of cookies | ||
Jessica Ruby edited English subtitles for The chemistry of cookies | ||
Andrea McDonough edited English subtitles for The chemistry of cookies |
Krystian Aparta
The English transcript was updated on 2/13/2015.