A Sweet Tooth Goes to Potions Class
Posted: September 26, 2012 Filed under: Uncategorized | Tags: baking, cookies, food chemistry, ingredients 1 Comment »Very few people get in a snit over cookies. But even though most people like them, everybody has a different idea about what makes a perfect cookie. Should it be chewy, thick, crunchy, or crisp? It turns out there is some fascinating food chemistry behind cookie texture. A lot depends on how much a cookie spreads, and when it sets. When you know how different fats, proteins, and sugars act in cookie dough, you can mix and match for your perfect cookie texture.
Imagine you’re making cookies. You put nice balls of dough on a cookie sheet, pop them in the oven, and a few minutes later these round, flat things come out. What happened to the balls of dough? They have spread as various ingredients liquify and interact. One of the biggest factors in the chewy or crispy fate of a cookie is the rate at which the cookies spread, as well as when they start spreading. The bottom line is, the more spreading that happens, the thinner and crispier the cookie, and vice versa.
So the cookies are in the oven, spreading out into cookie shapes. Now, when the cookie sets has a lot to do with the final texture of the cookie. Setting is baking terminology for when the proteins from the eggs and flour gluten physically rearrange before rejoining in a new overall structure. Once the proteins have settled in a new framework, the cookie has set. The cookie dough is no longer cookie dough, but an underbaked cookie. The faster a cookie sets, the less it spreads, making a thicker, denser cookie, and vice versa.
How to control rates of spreading and setting? Keep an eye on the type and amount of fat, protein, and sugar you use. Simple, right? Except there are a myriad of options and possible combinations.
the perfect cookie?
To promote spreading, use a solid fat in your cookies, such as butter or margarine. Solid fats tend to melt at lower temperatures, causing cookies to start spreading earlier and spend more total time spreading out into a thin, crispy cookie. It takes a higher temperature to get the molecules in liquid fats, such as vegetable oil or melted butter, up and dancing. Cookies containing liquid fats start to spread at higher temperatures, after more time in the oven. Starting the spreading process late means they do less of it, and end up thicker and denser.
The type of sweetener you use also affects the final cookie texture. Sugar is hydroscopic, meaning it readily absorbs water, both liquid and from surrounding air. When more water is absorbed, less of it evaporates during baking, leaving a moister, chewier cookie. Some sweeteners are more hydroscopic than others, however. White granulated sugar turns out to be not very good at absorbing water. Honey, maple syrup, molasses, or brown sugar are examples of more hydroscopic sources of sugar. Brown sugar, much more hydroscopic, will keep absorbing water even after baking, keeping cookies moist and ready to go in your mouth. Because cooking with white sugar leaves a fair amount of water moisture still in the cookie dough, this also helps it spread more than dough made with brown sugar.
Chewy cookie lovers- avoid this stuff!
Fats, sugars, and… proteins! The two main protein sources in cookies are flour and eggs. Flour provides the protein gluten, which binds ingredients together and provides chewiness. Different types of flour have different gluten content, with cake flour on the low end of the scale and bread flour at the high end. Eggs, or more specifically the egg yolk, also provide binding proteins. The higher the protein content (from gluten and eggs or egg yolks) in cookie dough, the less it will spread, as the proteins reassemble and latch onto each other into a new solid framework. No matter how much protein you have, high amounts of fat and sugar will get in the way of the proteins finding each other, and the cookie setting. Reducing amounts of fat and sugar in the recipe helps cookies set more quickly- the proteins can find each other faster!
The last key ingredient in cookies is… air. How much air is incorporated into the dough affects the final density and the crispiness of the cookie. Liquid fats can’t trap as much air into the dough as solid fats can, especially when the recipe calls for softened butter to be creamed with the sugar, incorporating even more air. When cooked, this air steams up and creates air pockets in the cookies as they set. Without the air, the cookies end up much more dense. Butter and margarine also contain a fair amount of water, which, once it evaporates off as steam, leaves air pockets and a crispy cookie. Egg whites, which are approximately ninety percent water, and only ten percent protein, also add air pockets as their water evaporates, along with some extra protein. Beating them before adding adds even more air, resulting in cookies of the crispy and not-so-dense variety.
Salivating for a rich, moist, chewy, thick, dense cookie? Pull out the brown sugar and melt the butter or use vegetable oil. Find the bread flour, maybe add an extra egg or egg yolk. Don’t use very much of the sugar or fat. Or would you rather a crispy, crunchy, thin, not-so-dense cookie? Go for the solid fats and whip them up with lots of air and sugar. Get some cake flour, and add an egg white beyond what the recipe calls for.
Of course, rarely do all of the stars line up and you have several cups of both brown sugar and bread flour in your pantry, in addition to remembering to melt the butter. But now you know why cookie recipes say to cream the butter and the sugar, why they often call for some white sugar and some brown sugar, and why the number of eggs varies with every recipe. You’ve always wondered, right? Now you can be your own potions master, and whenever you’re hankering for the perfect cookie, you know how to make it. And you’ll know why it works.
Images of Architecture, Architecture of Images: Computer Reveals Patterns in Cities
Posted: September 21, 2012 Filed under: Uncategorized Leave a comment »In his famous 1903 essay “The Metropolis and Mental Life,” sociologist Georg Simmel wrote that “with each crossing of the street” the city bombards its inhabitants with “rapid crowding of changing images, the sharp discontinuity in the grasp of a single glance, and the unexpectedness of onrushing impressions.” Simmel’s notion of the city as a chaotic jumble of images resounds to this day. But a new study suggests that if one looks closely enough, architectural features emerge that contribute to a city’s distinctive “look and feel.”
Combining computer science and urban architecture, a team of researchers at Carnegie Mellon University and INRIA/Ecole Normale Supérieure looked to Google to unlock patterns in visually complex places like cities. They developed an algorithm that can automatically detect and analyze Google Street View images of twelve cities around the world. They found that these images revealed stylistic architectural elements unique to those cities, such as Paris’ traditional street signs, balustrade windows, and balcony support as distinct from London’s neoclassical columns, Victorian windows, and cast-iron railings.
At left, Paris’ traditional street signs, balustrade windows, and balcony support are distinct from London’s neoclassical columns, Victorian windows, and cast-iron railings, at right. [Courtesy of http://graphics.cs.cmu.edu/projects/whatMakesParis/%5D
Mining through the virtual landscape of twelve cities for key Parisian elements is like “finding a few needles in a haystack,” the researchers wrote. They collected tens of thousands of Google Street View images and further divided each of those into 25,000 square patches. The researchers wanted to hunt down objects that were both frequent (occur often in Paris) and discriminative (are found only in Paris). For example, trees and cars appear everywhere in Paris, but so do in other cities; the Eiffel Tower is unique to Paris, but since there’s just one, it can tell us little about the city as a whole.
Programmed to recognize objects in images (similar to face detection in cameras and Facebook), the algorithm randomly sampled the patches of images to identify matches, starting with nearby neighbors (images from inside as opposed to outside of Paris). Through repeated sorting, the algorithm was able to build clusters of similar patches by filtering out uninteresting images like sidewalks or the sky found in all cities until elements common but unique to Paris remain.
Visual data mining analyzes tens of thousands of Google Street View images to seek out patterns unique to Paris, above. [Courtesy of http://graphics.cs.cmu.edu/projects/whatMakesParis/%5D
The program can also spot even subtler patterns. For instance, balcony railings are commonly found in main boulevards, while window railings dot the smaller side streets of Paris. And while arch-supporting columns have made Place des Vosges famous, they also appear in the more recent Marché Saint-Germain.
Similarities across cities also emerged, possibly indicating cross-cultural exchange. In the five European cities studied (Paris, Barcelona, Milan, London, and Prague), double arches are found everywhere except for London. Cast-iron balcony railings also appear frequently in Paris, Barcelona, and Milan, while railings in London and Prague are made of stone.
The algorithm had greater trouble characterizing American cities, mostly coming up with cars and road tunnels. The researchers suspect this failure is due to the “melting pot” of architectural styles and the dominance of cars in America.
This new tool may prove particularly useful for computer graphic modelers for films like Pixar’s Ratatouille, which needed to recreate Paris in an animated format. Beyond cities, this technology can potentially seek out patterns in nature, like fields and rivers, and even in home products, like cars and electronics, said the researchers. Can this tool also tap into Google Sky or Google Art Project to uncover patterns in the constellations or in paintings? The possibilities seem enticing.
So is the city, like Simmel once claimed, an onslaught of senseless images? Visual data miners say no. With further advances in this technology, we may perceive and understand our surroundings in a new light.
The Revolution Will Be Clumpy
Posted: September 19, 2012 Filed under: Uncategorized | Tags: climate change, clumped isotopes, dinosaurs, foraminifera, geology, human evolution, isotopes 1 Comment »Geologists are able to tell you the exact history of the waxing and waning of glaciers over the past five million years because microscopic creatures in the ocean have been unwittingly recording this dance in their shells. Their shells are made from the carbon and oxygen found in seawater. As glaciers form, seawater is removed from the ocean and trapped on land, resulting in subtle changes in the chemistry of the ocean. These changes are recorded in the shells, which create a detailed history as they pile up on the ocean floor.
The microscopic shell of a foraminifera. Shells from these creatures are commonly used in isotopic studies of past climate.
For decades paleoclimatologists have used the records of seashells to reconstruct either the volume of glacial ice trapped on land or the temperature history of the ocean, providing a beautifully detailed picture of climate over the past 5 million years. These approaches, however, are limited by the fact that the scientist must know the exact chemistry of the water that the shells were formed in to calculate temperature, or the exact temperature at which they formed to calculate the chemistry of the water. This fact has confounded hundreds of studies about the history of our planet. A revolutionary new method has solved that problem. It also has its sights set on topics as diverse as the biology of dinosaurs and the evolution of man.
These methods work because some molecules of the same element have different masses. These variants are known as isotopes. Many of these isotopes are unstable, meaning they break down into other elements while releasing harmful radiation. Just as important to geologists, though, are the stable ones – atoms that exist for eternity with a fixed number of protons and neutrons. Carbon has two stable isotopes, one with an atomic mass of 12, and one with an atomic mass of 13. Similarly, oxygen as three: masses 16, 17, and 18. In both cases the light isotopes are common, while the heavier ones are exceedingly rare.
Because of these variations in mass, nature treats the heavy isotopes slightly differently than the light ones. When the shells of ocean creatures are formed, they form with a fixed ratio of heavier and lighter isotopes, leaving hints about environmental conditions at that time. These ratios are trapped in carbonate, a molecule that contains one carbon and three oxygen atoms and is the primary building block of seashells (among many other things).
Relative changes in the temperature of the ocean at the time the shell formed can be calculated using these ratios. This is because at colder temperatures oxygen 18 and oxygen 16 behave more similarly than at warm temperatures, when increased energy makes oxygen 16 more likely to react and form carbonate than oxygen 18. Shells that form under colder temperatures, then, will have more oxygen 18 than at warm temperatures.
A record of climate for the past 540 million years derived from the ratio of oxygen-18 to oxygen-16 in marine fossils. Absolute temperature values cannot be derived using this method.
Information like this is critical if we wish to understand how our climate system operates, and what changes humanity will face as our planet continues to warm. But actual temperature values (i.e. degrees Celsius) would be even more useful.
Using oxygen isotope ratios to calculate absolute temperature is problematic, though. This ratio is also affected by the amount of oxygen 18 and oxygen 16 in the water to begin with. Ice prefers to form from oxygen 16. Therefore as more ice is trapped on land, more oxygen 16 is stripped from the ocean water. This results in oceans with more oxygen 18 in glacial times. This is the principle that is employed when scientists study shells to reconstruct the history of ice ages, but it means that more than one process can affect the oxygen isotope ratio in shells.
Because fluctuations in this ratio can be driven by both temperature and the original isotopic composition of the seawater, a researcher could not simply take, for example, a 65 million year old seashell and tell you the temperature of the water was when it formed. Absolute temperature values are almost impossible to calculate from oxygen isotopes in older carbonate samples.
That was before 2006, before the term ‘clumped-isotope’ entered the geologic lexicon and revolutionized the use of isotopes to study temperature. Using a new method known as ‘clumped-isotope paleothermometry,’ a researcher could indeed pick up a 65 million year old seashell and tell you the temperature in which it was formed without knowing anything else about it.
While the technique represents a complex and technical scientific achievement, the premise behind the method is fairly straightforward. When a carbonate molecule forms with more than one heavy isotope, the bond holding that molecule together is stronger than if it formed with only the common light isotopes. Before a carbonate mineral is formed and locked in place as a bone, shell, or rock, the carbon and oxygen atoms dance around, repeatedly switching partners. Because of this dance, you might expect a random distribution of light isotope to light isotope bonds (i.e. carbon 12 bonded to oxygen 16) and heavy-to-heavy bonds (i.e carbon 13 to oxygen 18).
The beauty lies in the fact that this is not the case. Because heavy-to-heavy bonds are stronger, they last just a little bit longer than the other arrangements. This is especially true in cold conditions, when there is less energy to break bonds to begin with. The higher the temperature in this sea of isotopes, the more chaotic the dance becomes. With more chaos, the ability for heavy-to-heavy bonds to remain together is reduced, and eventually removed, yielding the random distribution of bonds one might expect. The result is simple: carbonate formed in cool conditions will have more molecules with more than one heavy isotope, whereas carbonate formed in warm conditions will have fewer.
The process by which heavy isotopes join together is referred to as ‘clumping,’ and with the advent of new and highly sophisticated laboratory equipment, scientists can measure the degree to which it has occurred in carbonate. Years of experiments have related the amount of clumping in carbonate directly to temperature. Best of all, the starting composition of the water that formed the carbonate is irrelevant. If it formed at the same temperature, a researcher will get the same value whether large amounts of oxygen 16 were removed from the ocean by ice or not.
Ocean temperatures are not the only questions that can be addressed using clumped-isotopes, though.
Drs. Benjamin Passey and Naomi Levin at Johns Hopkins University, for example, are interested in human evolution. They wanted to tackle an old but important question: was the time period that led to the emergence of hominids cooler than the present in key anthropologic sites in Africa? Some researchers have said yes, but many have suggested that it was significantly warmer than present.
Many theories of human evolution depend on knowing what the environment was like at this time, so Passey and Levin decided to apply clumped-isotope methods to fossilized African soil (soil commonly contains carbonate minerals). They found that temperatures over the past 5 million years have been either the same as, or warmer than, the present. This limits, in their view, any hypothesis relating the evolution of human traits to those that can be explained by similar or warmer temperature to the present.
Jumping back many millions of years, Dr. Robert Eagle at Caltech wanted to know more about the metabolism of sauropod dinosaurs, massive creatures like the famous Brachiosaurus. A long-standing debate amongst paleontologists is whether these creatures were cold-blooded, deriving their energy from the environment like modern day reptiles, or if they possessed some form of endothermy, maintaining their body heat internally as mammals and birds do today.
A brachiosaurus looking unconcerned about finding warmth from the environment.
Because the bone and teeth of vertebrates are composed of bioapatite, a carbonate mineral, Eagle decided to use clumped isotopes to tackle this question. Previous work on modern animals has shown that the temperatures derived from teeth are representative of body temperatures. So in a 2011 paper, he looked at the temperatures recorded in the fossilized teeth of sauropods. He determined that the temperature at which the bioapatite in their teeth were forming was much higher than those for modern reptiles, similar to mammals, but lower than birds. This ruled out a cold-blooded dinosaur, and posed new questions about dinosaur biology.
Clumped-isotope paleothermometry is still in its infancy, but it is rapidly expanding. 2006 was the first year any paper used the term “clumped-isotope.” In 2011, 19 papers did, and many more are on the horizon.
Still many kinks need to be worked out. Methods need to be standardized and conclusions need to be scrutinized. Undoubtedly a period of time will come, as is the case with most scientific developments, where researchers identify more and more problems, adding a dose of reality to optimism. For now, though, the slight preference for some isotopes to stay bonded together is ushering in a new world of possibilities for earth scientists. This is the beginning of something big.
Rachel Carson and the Power of Science Writing
Posted: September 15, 2012 Filed under: Uncategorized | Tags: climate change, endocrine disruptors, pesticides, Rachel Carson, science writing, Silent Spring 2 Comments »Is the pen mightier than the sword? Fifty years ago this month, one of those rare books was published that seems to have proven the famous saying true. Powerful industries opposed the book, but only succeeded in increasing its renown. President Kennedy appointed a commission to investigate; the commission reported that the author’s findings were correct. The book galvanized an environmental movement, led to laws and regulations that protected the country’s air and water, and brought treasured species like the bald eagle back from the edge of extinction.
The book, as you might have guessed, was Silent Spring, and the author Rachel Carson. Today we might wonder how such an influential writer could ever have emerged, but in the 1950s and ’60s Carson was a celebrity. And it wasn’t for writing scary books about pesticides; her main beat was the ocean. Carson became most famous for The Sea Around Us, which told the public about the stunning advances in scientists’ understanding of marine life. “With that book Carson not only became an international superstar, she became the most trusted voice in public science,” says Linda Lear, who wrote a biography of Carson. “She never wrote any article for the academic community. She wrote for the public, because she wanted the public to understand the world they lived in, the natural world.”
The Book of the Month Club edition of Silent Spring, with Supreme Court Justice William O. Douglas’s endorsement. Source: wikipedia
Carson was able to write authoritatively about science in part because she came from the academic science community; she earned a master’s degree in zoology from Johns Hopkins University in 1932. Today she might have moved naturally over to that university’s science writing program (where my co-bloggers and I now reside) and launched her career that way, but in her day she was forced to blaze her own trail. She attempted freelancing, which was apparently no easier then than it is today, but also got herself noticed by the Bureau of Fisheries (now the US Fish and Wildlife Service), where she was hired to translate marine science into accessible prose. Though she excelled at this job and moved up through the government bureaucracy, she was also setting herself up for an independent writing career. “What she really wanted to do is publish her way out of government,” says Lear.
So Carson was a science writer who started out, like many, as a celebrator of science. But because of her scientific training, she recognized the dangers that certain scientific advances—especially those in atomic physics and chemistry—posed to the ecosystems she loved. However, Silent Spring is not anti-science; rather it uses science to questions humans’ use of scientific knowledge in the post-World War 2 period. In answering these questions, Carson makes full use of her prodigious writing skills, eloquently synthesizing the best government and academic science of her time.
It would be nice if we could say Carson’s pen had vanquished the overuse and misuse of toxic pesticides, but with a few notable exceptions like DDT, most of them are still around. And as anyone who reads the news knows, the world is awash in all kinds environmental threats—endocrine disruptors, farm runoff, greenhouse gases. So where are the next generation (or two) of Rachel Carsons—writers who bring a scientific issue to the public’s attention and inspire citizens and politicians to act? Nancy Langston, environmental historian and the University of Wisconsin-Madison, says part of the problem is the sheer amount being written. “Every time another book comes out such as…Our Stolen Future—that was the first really popular account of endocrine disruptors—people say, ‘Oh, it’s the next Silent Spring,’ but there are dozens of these each year. And I think a lot of people get overwhelmed.”
I’m particularly curious what Carson would have done with climate change, the most pervasive environmental threat today. After all, many talented science writers have taken up their pens (or more likely their computer keyboards) in the hope of overcoming the ignorance and inertia surrounding this issue. One who stands out for me is Elizabeth Kolbert, whose brilliant book Field Notes from a Catastrophe (which, like Silent Spring, was first serialized in the New Yorker) places climate change in its terrifying, civilization-destroying historical context. But did Field Notes lead to a presidential commission? Has legislation been passed? Have most Americans even heard of this book? Unfortunately, the answer to all three of these questions seems to be no.
It isn’t the fault of Kolbert or any other writer. The industries and groups opposing action on climate change are far more organized and sophisticated than those Carson was up against. “With climate change this isn’t just a debate, there’s a well-oiled machinery that actively propagates doubt, and is invested in that, and is tied up in the fossil fuel industries, and in making sure that legislative inaction is perpetuated,” says Rob Nixon, an environmental writer and Rachel Carson Professor of English at the University of Wisconsin-Madison.
Nixon does point to Bill McKibben’s recent Rolling Stone article “Global Warming’s Terrifying New Math,” where he writes that enough fossil fuel reserves are already on the books of major oil companies to warm the planet far beyond 2 degrees Celsius, the limit of what scientists believe might not be catastrophic. McKibben “has committed himself very squarely to this topic, very single-mindedly, so I think he’s the closest we come” to Carson today, says Nixon. Without question, McKibben’s article earned a lot of attention; for a week or two I found myself in conversations about it almost daily. But only for a week or two. The article also has the danger of doing exactly the opposite of what he probably intended: making the problem look so massive, and the industries driving climate change so mighty, that there is nothing we who have only our pens can do.
So can we still earnestly go around saying, “The pen is mightier than the sword.”? This famous line, from a now-obscure 19th-century play, encapsulates a sentiment that has probably given succor to many an idealistic writer, perhaps even Carson. And it would seem to follow that with the rise of the Internet and self-publishing, the daily avalanche of words would be enough to overpower any opposing force. But the opposite is true: with more words published than at any time before, each one seems to matter less. It’s hard to break through, and even harder to last: trending today, gone tomorrow. Will anyone recapture Carson’s gift for cutting through the fog? I don’t know, but for the sake of all members of the community of life, I certainly hope so.
* * *
Postscript: for my own amusement, I decided to try updating the famous line for the bureaucratic age. Let’s see if this proverb catches on: “Writing is a more effective means of advancing change than military action.”
Ready, Set, Tell Me A (Science) Story
Posted: September 11, 2012 Filed under: Uncategorized Leave a comment »
The friendly takeover is complete! We’re all excited to start gold digging for stories in the world of science, and share what we sift out with you. And we would like to introduce ourselves, those doing the taking-over, before we plunge in as new bloggers. We’re an eclectic bunch, but we’re all interested in translating science into compelling stories.
Alex Kasprak comes to us from Brown University, where he recently earned a M.S. in geological sciences. There, he studied marine, environmental, and ecologic change during one of the largest biotic catastrophes known to the fossil record – the end-Triassic mass extinction. His favorite geologic age is the Hettangian, his favorite animal is the mouse lemur, and his favorite element is sulfur.
Jean Mendoza graduated from Brown University with a degree in English and biology, passions which she combined into science writing at Johns Hopkins. Her interests span from the intersection of science and superstition to medicine and astrophysics. She draws inspiration from Hemingway, Fitzgerald, Joan Didion, Jenny Boully, and Annie Dillard.
Gabe Popkin has come most recently from Madison, WI, and before that from the Washington, DC area, where he worked full-time for the American Physical Society for several years. Gabe has a physics degree from Wesleyan University, and over five years of professional science writing, editing, and communication experience. He loves writing about physics, ecology, and everything in between–with a particular interest in the interactions between humans, our environment, and the rest of life on earth.
Kelsey Calhoun spent last year as a neuroscientist playing with rats, and is here to play with words because rats really can’t keep a discussion going when it comes to the physics of harpsichords, or the chemistry of chemotherapy. She’s interested in almost every field of science, but particularly neuroscience, genetics, ecology, and anything interdisciplinary. When not writing, she enjoys making music, biking, and watching live tropical fish cams.
If you have a comment, idea, suggestion, or question after reading what we write, please comment (we love discussing these cool stories). We’re on twitter too, @the_sieve. If you like what you read, share it! We hope you enjoy our stories, wonderings, and explorations.
A Friendly Takeover
Posted: September 9, 2012 Filed under: Uncategorized Leave a comment »
Passing the Sieve to the next generation
The four of us — Emily, Sara, Jay and myself — started this blog so we could enjoy a little freedom to write what stories we pleased. We also wanted to get a taste of having our science writing out where more people could see. It worked out pretty well. Sure, our activity has come in peaks and valleys as we’ve balanced the blog with work and school. But now that we are all in the early stages of life after grad school, I think we can all look back on this blog and see writing to be proud of.
We also hoped the blog could be one more thing. Wouldn’t it be cool if The Sieve could become a mainstay of science writing at Johns Hopkins? At the start of 2012, it was hard to say whether our little trial run would become a budding tradition. But that likelihood seems to be growing, because four new science writing students have agreed to take the blog on for the 2012-13 academic year.
So this post is to pass The Sieve to the next generation of Hopkins science writers. From this point forward, the blog is theirs to do with as they please. I looking forward to seeing posts from Alex, Kelsey, Gabe and Jean as they navigate the blogging waters!
Keep on Siftin’!
Sean
