Credit: jypsygen/Flickr

Opening the refrigerator to find a gallon of spoiled milk is a rotten way to start the day. But for fresh cheese makers, every day begins with sour milk. Here’s why: 80% of the proteins in milk belong to a family called caseins. Adding acid to milk, like lemon juice or vinegar, makes these invisible proteins visible as a white, chunky solid we call the curds.

In a glass of milk, caseins aggregate into small spheres called micelles. The outside of each protein cluster is negatively charged, causing neighboring spheres to repel each other. Thus, these micelles remain evenly distributed throughout the milk.

Acidic vinegar neutralizes the negative charge on the spheres. With the repulsive force gone, the protein clusters clump together and form an observable solid, the curds. When chefs collect the curds and discard the liquid whey, they have queso fresco. Try it yourself with this recipe.

Stretching the hot curds instead of pressing them into a cake gives you homemade mozzarella cheese. I've tried to make mozzarella using this kit, but it only worked once. That's because the quality of the curds depends on the type of milk that you use.

Credit: poopoorama/Flickr

Most milk from the grocery store has been ultra-pasteurized, meaning it's been heated to temperatures above 172° Fahrenheit. That extra heat disturbs the casein proteins. Curds from ultra-pasteurized milk don't stick together and stretch as nicely as they do when made from milk that has been pasteurized. I've had a hard time finding milk not labeled UP or UHP, so I haven't tried to make mozzarella at home again.

But now I'm hankering for a mozzarella, tomato and basil salad. Guess I'd better find some pasteurized milk before summer comes!

Image credit: Flickr/great_sea

Dogs’ amazing sense of smell can help police officers find lost people, illegal drugs or smuggled food. Scientists use trained sniffer dogs to track pythons in the Everglades or find whales by smelling their floating poop. And some dogs can smell cancer too.

Scientists are working to build devices that can detect odors as sensitively as a dog’s nose. Now researchers in South Korea have built a sensor that works like a dog’s nose, without using canine sniffing cells. The new device combines a simplified version of the cells in dog’s nose with tiny transistors similar to those in our computers. It senses hexanal, a chemical commonly released by rotting food.

When a dog takes a whiff of something (possibly stinky to us!), chemical vapors bind to matching proteins on the surface of different cells in its nose. Binding of the aroma molecule sends a cascade of charged ions coursing through the cell. Those ions create an electric field that travels through the cell. This chemical and electrical wave travels along connected cells and neurons until it reaches the dog’s brain as a nerve impulse, signaling that the animal encountered that particular smell.

Tai Hyun Park and Seunghun Hong, of Seoul National University, with their colleagues, recreated a simplified version of the detecting cells in a dog’s nose using tiny bubbles made from cell membrane. The scientists engineered human kidney cells to produce the canine receptor protein for hexanal, a chemical released by rotting food.

These cells naturally contain a handful of accessory proteins that generate the ion cascade once the smell molecule binds to its receptor. The researchers shook the engineered cells and tiny bits of membrane pinched off into tiny bubbles that contained the dog receptor protein and the accessory proteins (see left side of the picture below).

Diagram of new sensor. On right: The bubble contains dog smell receptor protein (labeled olfactory) and accessory proteins that allow calcium ions to flow inside when the receptor protein binds hexanal. The bubble sits atop a web of carbon nanotubes. Left: Calcium ions flow into the bubble when the receptor protein binds the target, hexanal. Image credit: Seunghun Hong, Seoul National University in Korea

Then the scientists placed these bubbles atop a web of conducting carbon nanotubes, hollow cylinders made from carbon sheets. When the receptor protein in the bubble captures hexanal, the other proteins begin the chemical cascade that ends with calcium ions flowing into the bubble (right side of the picture above).

The new sensor does not detect the electric field created by those ions, as a dog’s brain eventually would. It measures how that electric field influences current flowing through a nanotube transistor.

In the transistor, carbon nanotubes stretch between two electrodes and current flows freely through the nanotubes. The positive electric field created by the ions inside the bubble repels the positive charges zipping through the carbon nanotubes. Without free flowing positive charges, the nanotube cannot easily conduct electric current. So when hexanal binds to the bubble, calcium ions rush inside and the sensor reports a decreased electric current (Analyst, DOI: 10.1039/c2an16274a). The more hexanal, the lower the reported current.

The sensor could detect the 6-carbon hexanal chain even when it was mixed with similar chemicals 5-, 7- and 8-carbons long. It even signaled when covered with diluted spoiled milk.

Hong says that these sensors could be used to evaluate the quality of wine, coffee and perfume by standardizing and quantifying their smells. Dogs have 220 million different smell receptors (pdf). But there’s no need to make one sensor for each smell receptor in a dog’s nose, Hong says. Perhaps scientists would need 10 to 20 different sensors that correspond to the characteristic odors of the wine or coffee, he says.

The Titanic, April 1912 Credit: Wikimedia Commons

This past Sunday marked 100 years since the Titanic sank in the icy waters of the northern Atlantic Ocean. Yet after all this time, questions still remain about what really caused the ship to go down.

Often an errant iceberg gets all the blame. Others chalk up the disaster to human error. And a new book posits that odd weather conditions caused a hazy mirage that hid the iceberg from sight.

In her most recent video, materials scientist Ainissa Ramirez, at Yale University, looks at two theories of how metals used to build the ship could have contributed to the damage.

One theory is that the frigid water cooled the ship’s hull enough to change its mechanical properties from flexible to brittle. If so, the metal sheets would crack easily upon impact, instead of denting like a car that’s been in an accident. If the boat was in warmer waters when it hit the iceberg, perhaps the gash in the hull would have been smaller, Ramirez says.

In her video, Ramirez demonstrates how temperature can change flexible materials, like rubber, into brittle materials that shatter like glass. Rubber is a tangle of strands called polymers. Normally, individual polymer strings slide past each other like noodles in a bowl of spaghetti, she says. These strands stiffen as the rubber cools, making the material brittle and easily broken.

At the end of the video, Ramirez mentions another theory for how materials contributed to the Titanic’s demise: the rivets that held the metal sheets together were inherently weak. The manufacturing process for these rivets introduced clusters of impurities into the iron. These clusters disrupt and weaken the neat network of atoms in a strong metal. Clumps can lead to cracks. And cracked rivets cause open joints.

Metal workers used to identify strong rivets by listening for a ting as they pounded the rivets into a joint. But workers building the Titanic could not hear this sound because they pounded in the rivets using noisy hydraulic hammers, Ramirez says. Perhaps if they built the boat by hand, workers could have heard that these rivets were not ideal, she says.

If you’re hooked on materials, learn about the tiles that keep the space shuttle cool as it enters our atmosphere, how materials can convert heat to electricity to power a cell phone and more from Dr. Ramirez’s videos at Material Marvels.

Californians didn't just invent iPads and commercial microprocessors; they brought to life laws promoting clean water, clean air, laws that eventually went on to become national policy, credited with cleaning up vast swaths of the country.

An average-sized sofa can contain two pounds of flame-retardant chemicals.

But sometimes, the picture is less clear. That’s the case with TB 117, a pioneering California law that many scientists now say was a big mistake.

One of those scientists is chemist Arlene Blum, a visiting scholar at the University of California, Berkeley and founder of the Green Science Policy Institute, a non-profit group in Berkeley.

I met Blum at a furniture store in Berkeley. Standing in front of a three-seated sofa, she lifted a cushion and read aloud from the small white tag sewn into the fabric.

“This article meets the flammability requirements of the California Bureau of Home Furnishings Technical Bulletin 117."

A California law's mixed legacy

TB 117, as it’s called, is a state law passed in 1975. It says that the foam inside upholstered furniture must be able to resist a flame, for example, from a cigarette lighter, for 12 seconds without catching fire.

Manufacturers meet this law by treating the foam with several different kinds of chemicals, up to two pounds of flame retardant chemicals in an average-size sofa, according to Don Lucas, a flammability expert at Lawrence Berkeley National Laboratory.

Even though the law is specific to California, it affects furniture sold across the country. Major furniture dealers sell California-compliant products in all 50 states, and Canada.

The problem, say Blum and others, is that the chemicals don’t just stay inside the sofas. They turn up in household dust and can be detected in human blood and breast milk. Toddlers often have higher levels of the chemicals in their bodies than adults do.

"One study found that the levels of PBDEs found in bodies of toddlers are similar to what you'd find in people who work in a recycling foam factory. That's two to ten times what you'd find in adults," says Ami Zota, a researcher with UCSF's Program on reproductive Health and the Environment.

"There's a growing body of evidence demonstrating effects in animals, and not just lab animals, but birds and marine mammals," says Linda Birnbaum, who directs the National Institute of Environmental Health Sciences of the National Institutes of Health.

Birnbaum says while effects in humans are less certain, there is good evidence to suggest that some flame retardants, particularly a class called PBDEs, which have been largely phased out sine 2004, can affect the reproductive system, nervous system, as well as learning, memory, and behavior in children.

Some flame retardant chemicals cause cancer in lab animals. Observational studies of humans suggest connections between the chemicals and infertility, low-birth weight and abnormal brain development in kids.

One chemical, known as tris, was used widely in children's pajamas until the 1970s, when scientists, including Arlene Blum, campaigned successfully for a phase out. Tris is considered carcinogenic under California's Proposition 65 but is still used widely in furniture and also turns up in baby products, such as nursing pillows and changing pads.

Industry fights change

State lawmakers have tried — and failed — five times to change California's law in ways that would reduce or eliminate the use of flame retardant chemicals in furniture.

Four of those attempts came from one lawmaker, State Senator Mark Leno, who represents Marin and San Francisco.

Leno’s last bill, SB 147 had the support of furniture makers, firefighter groups, and doctors. All of them wanted the chemicals out of furniture. But the bill was killed in committee by a vote of seven to one.

Each of the lawmakers who voted on the bill had received campaign contributions from the chemical industry.

Leno says it's not hard to see those lobbying dollars in action.

Whenever one of his flame retardants bills would come up for a vote, he says, he’d pay a visit to each of the committee members, just before the vote, to make his case. But the lobbyists outnumbered him.

“Repeatedly, as I would leave a colleague’s office, an hour or two before the committee hearing racing to get to another office, in the waiting room of the office I’m leaving is a lobbyist for the chemical industry. So they’d have the last word,” says Leno.

(Update: Read about how a Seattle burn doctor misled California lawmakers with the fictional story of an infant burn victim in the Chicago Tribune's four-part series, "Playing with Fire.")

In February, a state lawmaker, Assemblywoman Holly Mitchell, from Los Angeles, introduced — and then quickly withdrew — her own bill on the topic. A spokesperson said Mitchell decided she was too busy, but would pick it up next year. Since 2011, Mitchell has taken $3,500 from the chemical industry.

(For more on how campaign dollars from the chemical industry have helped keep flame retardants in furniture, see Liza Gross' 2011 special report in Environmental Health News, "Money to Burn.")

It’s hard to find supporters of TB 117 who aren’t in some way connected to the same companies that produce flame retardant chemicals.

Joe Lang is a former tobacco lobbyist with the firm Lang, Hansen, O'Malley & Miller, in Sacramento, whose clients include the American Chemistry Council, a chemical industry group.

At a hearing last April, Lang argued that changes to the California law are unnecessary because many of the most harmful flame retardants, a group called PBDEs, have already been banned. Newer alternatives, he said, are safer than the old ones. He said that over-regulating this industry would squelch innovation.

“If we continue to ban chemicals that are developed before they're used, we won't have any chemicals to be used. We won't be able to create the jobs we want to create in California.”

Do flame retardants in furniture prevent fires?

Lang and others in the industry say that flame retardant chemicals, and the law that requires them, TB 117, serve a critical purpose: They prevent fires.

Donald Lucas, the Lawrence Berkeley National Lab scientist, and his colleague Vyto Babrauskas researched exactly this question: Do flame retardant chemicals prevent fires?

“Our conclusions were that we really don’t need the flame retardants in the foam in home furnishing," said Lucas. We don’t think the TB 117 standard is very good.”

The chemicals don’t work, he says, because fires don’t start inside sofas. They start on the surface of the sofa, on the fabric. California's flammability law, TB 117 law says nothing about the fabric, just the foam.

“Once the fabric catches on fire, the flame that the foam is exposed to is much larger than the flame in the test,” says Lucas.

At that point, there’s nothing chemicals can do. It’s too late.

“The foam is going to burn anyway.”

In fact, there are far fewer fires today than there were in the 1970s, when TB 117 was written. Fewer smokers, as well as laws requiring smoke detectors and sprinklers have made homes safer. These days, most fires start in the kitchen, not on a sofa.

That’s one reason even fire fighters have had a change of heart on the subject of flame retardants.

Tom O’Connor, a fire fighter in San Francisco, says fires these days are a toxic soup of chemicals, thanks, in part, to chemically-treated furniture.

O'Connor, and others, believe they're seeing an epidemic of cancers among firefighters. San Francisco's Fire Department is one of several around the country participating in a study of firefighters and cancer run by the National Institute for Occupational Safety and Health.

If flame-retardant chemicals in furniture are part of the problem, says O'Connor, "then obviously we want them out of the products of combustion, once we go into a burning building."

Given recent events in Sacramento, that change is unlikely to start happening, at least this year.

One California official could sidestep the legislature and change the law: Tonya Blood. She was appointed just last week as the new chief of the California Bureau of Home Furnishings. It’s the same agency that established TB 117 back in 1975. Blood’s office didn’t answer requests for an interview.

Image credit: Flickr/ jypsygen

It’s practically impossible to brew the same cup of coffee each day. New technology to analyze and automate coffee brewing helps anyone bring reproducibility to his or her morning coffee routine.

The perfect cup of coffee can be quantified in terms of its strength, also called total dissolved solids, and the percent of flavors extracted from the beans during brewing. Let’s get technical about the numbers.

Back in the 1960s, Ernest E. Lockhart, a researcher at the Massachusetts Institute of Technology, made pots of coffee with varying strengths and degrees of extraction. Then he asked people which brew they preferred. From that survey, and another follow-up by the Specialty Coffee Association of America, numerical standards emerged to describe the perfect cup of coffee: a brew with 1.15-1.35% dissolved solids and 18-22% of the possible flavors extracted.

You can measure these numbers for your coffee at home. A handheld device called a refractometer shines light through a droplet of coffee, measuring how much the light waves bend as they travel through the liquid. The amount of dissolved solids in the coffee – including sugars, acids, and flavors from the coffee as well as the minerals in the water — affect how much the light bends, and thus the reading on the device.

Refractometers for measuring dissolved solids in coffee and espresso. Image credit: Flickr/ Coffee Geek

Enter that percentage of dissolved solids from the refractometer, as well as the weight of water and beans you used, into an iPhone app called MoJoToGo to calculate the extraction percent.

In an article for Gizmodo, Matt Buchanan describes his quest to brew a cup of coffee with the extraction percentage sweet spot of 19%:

"I tear through a $16.50 one-pound bag of coffee in about three days, making coffee over and over again, seeking the mythical number 19. I use a version of the French Press technique from Everything But Espresso. Start the kettle. Weigh the beans. Grind the beans. Wait for the water to reach 206 degrees. Pour 400g of the heated water onto the grounds. Start the timer. Pat the coffee bloom. Dunk the coffee bloom. Wait 4-5 minutes. Plunge. Pour. Check result in MoJoToGo. Curse.

The most frustrating part isn't the resulting Ahab-like hunt for the ever-elusive 19 percent. It's the revelation of how imprecise my methods are. The 18.3 percent cup that sends me into a delirious orbit before I even taste it is quickly followed by one that measures 16 percent (and tastes like it). I'm all over the map. It drives me insane. And to Amazon, to buy more precise equipment."

Brewing the perfect cup of coffee by hand is messy, imprecise and frustrating. And again technology comes to the rescue. The Trifecta MB, a new machine made by Bunn, brings reproducibility to coffee brewing, one cup at a time.

It’s the home version of a commercial machine with 10 programmable functions, including water temperature, brew time and the amount of stirring with air bubbles, to precisely control brew conditions to highlight the best flavors in the beans. Watch the commercial version in action:

Portola Coffee Lab in Costa Mesa, CA has several Trifectas in the shop. Owner Jeff Duggan writes on the shop blog that he typically spends hours developing a unique brewing program for a new coffee.

"This machine has become the clearest example of our brewing standards," he writes. “It uses technology to put us more in touch with coffee rather than neuter it and make it into a new version of a vending machine.”

Armed with Portola’s program, a bag of their beans and your own Trifecta, you could brew coffee at home that tastes just like what they brew in the shop. Some roasters post their optimized programs on Trifecta's website so anyone can brew a tasty batch of their coffee.

Technology advances the artistry of coffee, for what really matters is taste. Gadgets, apps and machines help coffee connoisseurs find conditions that brew the best coffee according to their tastebuds, whatever that extraction percentage or brew time may be.

Image Credit: Flickr/eclectic echoes

There were many shaky hands at a regional coffee competition in Santa Cruz one weekend in early March, though it was hard to tell if the tremors were due to nerves or just the free-flowing coffee at the tasting bar.

Baristas from Colorado to Hawaii competed to earn a trip to the national championship in April. Brewer’s Cup participants, mostly from California, brewed a mystery coffee, tweaking their favorite brewing method to bring out the best flavors of that coffee. Winners from the first round used their own beans to brew in the finals.

As the brewing finalists’ recipes show, making the perfect cup of coffee is not as simple as adding hot water to ground coffee beans. The grind size, water temperature and brewing method can change the flavor. Coffee connoisseurs delight in controlling every detail. And even the corporate coffee giant Starbucks is experimenting with brewing. They’ve just opened a brewing “laboratory” in Amsterdam.

We describe an ideal cup of coffee in terms of its strength, aroma, flavor, acidity, and finish. Coffee enthusiasts quantify those descriptions as the concentration of coffee compounds in the final brew and the amount of flavor extracted from the beans.

Peter Molignano, of Fortnight Coffee Company in Los Angeles, competes in the Brewer's Cup of the South West Regional Barista Championship, Santa Cruz, CA, March 9, 2012. Image credit: Melissae Fellet

There are 2000 different flavor and aroma compounds in roasted coffee beans. Only a fraction of those flavors dissolve in hot water, and even fewer are palatable. A cup of coffee brewed to full extraction is bitter and undrinkable. So brewers aim to pull the sweet and complex flavors from the grinds before the beans leach their bitter compounds.

Reaching that extraction sweet spot depends on several factors, including the ratio of water to beans by weight. (Notice that all the winning recipes from the competition specify water and bean weight.) The size of coffee grounds and the brew time matter too. If your coffee is weak, grinding the beans finer increases the surface area of the grounds exposed to the hot water and thus increases the amount of flavors extracted. But watch the clock once the hot water hits the grounds. Brew any pot too long and those bitter flavors seep out from the beans.

Water temperature is another way to control the flavor of coffee. Water warmed to 195-205 degrees Fahrenheit is best, says Lalo Perez-Varona, an independent coffee researcher from San Francisco.

Coffee associations around the world recommend numerical standards that label the perfect cup of coffee in terms of the percentage of extracted flavors, but ultimately individual taste preferences determine excellence.

For a tasty cup of joe, pick beans with flavors that you like, use your favorite brewing method, and troubleshoot using this chart, changing one factor at a time.

Image credit: Melissae Fellet

Brewing method influences the flavor of the coffee too. Completely immersing the coffee in hot water, as in a French press, tend to brew coffee with more sweetness and body, says Perez-Varona. Paper filters trap some of the oils and solids, clarifying the flavors in the coffee.

Brewing with a siphon, also called a vacuum pot, gives you excellent temperature control due to the consistent heat source underneath the pot. This process is beautiful to watch:

I think a person's preferred brewing method is a chance to infuse their coffee with some personality and flair. Peter Molignano, of Fortnight Coffee Company in Los Angeles, brought his handmade wooden siphon holders to the competition in Santa Cruz. He warmed the upper part of the siphon with halogen lightbulbs mounted in a matching wooden box.

From precision analysis to the ritual of brewing, a cup of coffee is a union of science and art. Because my morning routine doesn’t leave time for experimenting with water temperature, brew time, grind size, and water and bean amounts, I’ll leave the science – and the art — to the experts at my favorite local coffee shop.

UPDATE 4/2/12: The underextraction-overextraction chart has been updated. The original picture had the last entries for the water to coffee mixtures switched.
UPDATE 3/22/12: The optimal water temperature for brewing coffee was originally reported as 192-203 degrees Fahrenheit. It has been changed to 195-205F.

Flowering Tea - Vassia Atanassova (Spiritia)

Every time I drive from the South Bay to the East Bay, I pass the Numi tea factory and start to crave a hot cup. I love tea–the ritual of heating and pouring the water, the warm mug in my hands and the slow sipping as it cools–and Numi makes some of my favorites.

Knowing this, a friend recently gave me a Numi gift box: "FLOWERING TEA^TM handsewn leaves blossom when steeped." Pleased but confused, I did some research, and quickly figured it out.

Did you ever get those pill-shaped foam toys when you were a kid? You'd throw one in water, the capsule would dissolve, and the foam would expand into a huge dinosaur or shark.

Flowering tea is the classy grown-up version of grow monsters.

Grow Capsules - Alibaba

The teas don't expand quite as much as the toys, so you might be able to guess they're using a different technology. Grow monsters showed up in the 1970s, using super-absorbent polymers originally developed for medicine and hygiene (think diapers). Super-absorbent polymers are long-chain molecules that bind with water so enthusiastically that they can absorb up to 500 times their weight. (I presume that's why it says "expands hundreds of times!" on some toy packages; an inch-long capsule certainly does not expand to a 40-foot dinosaur.)

Blooming teas don't contain any super-absorbent polymers—only tea leaves and flowers. But because they've been dried, they have a lot of room to expand when soaked in water again. A Star Trek alien once called humans "ugly bags of mostly water," and the same could be said of almost all Earthling animals and plants. Fresh tea leaves contain 75-80% water, but are dried down to 2-7% before being sold as tea (flowering or otherwise). When you add water to this dried biological bundle, it readily expands and uncurls according to the whim of the tea artist.

Numi's Dragon Lily (which I drank while writing this post)

Numi isn't the only place to get blooming tea–you can also find it at Red Blossom Tea Company and Peet's, among others.

Of course, San Franscisco hipsters are keen to debate whether it is truly hip or merely a "gimmick." Apparently, no one is sure how long blooming tea has been around. It might be just a few decades old (about the same age as grow monsters–coincidence?) but there are thousand-year-old Chinese references to "display teas." These weren't quite the same as modern blooming teas, because nobody actually drank the water the display teas were steeped in–they were strictly for entertainment.

Just like grow monsters, come to think of it.

A letter from the Revolutionary War with lines written in invisible ink. Credit: Wikimedia Commons

Last year, the US Central Intelligence Agency released documents detailing recipes for invisible ink from 1917 and 1918. Among the recipes was a favorite ink recipe of German soliders during World War I — crushed aspirin mixed with water. Though the ink is easily available, uncovering it required a complicated chemical developer.

Other recipes in the CIA documents used solutions of iron, silver or copper salts as ink and developed the writing by heating the paper. This bit of history inspired my inner scientist and spy. Without access to chemicals in a lab, I experimented with invisible ink recipes using things I found around my house.

1. Lemon juice and heat
Dip a cotton swab or thin paintbrush in lemon juice. Write your message on white paper and let it dry. Hold the paper over a lamp, radiator or candle (but don’t let it catch fire!). The heat breaks down the acid into light-brown compounds, revealing your message forever.

This is how my experiment turned out. The top part of the picture is the paper before I held it over a candle.

Using lemon juice as invisible ink, before and after developing with heat. Credit: Melissae Fellet

2. Laundry detergent and black light
White shirts glow under black lights at a haunted house because the whitening agent in laundry detergent glows under ultraviolet light. Try writing your message using liquid laundry detergent. Holding the paper to a black light reveals a glowing message without damaging the paper.

But if spies intercept a message written with one of these inks, it’s likely they could decode it. We all can find something to heat paper. And black lights, though less common than candles, are still widely available.

To solve this problem, I borrowed a trick from George Washington: using two different chemicals to write and decode the message. Washington wrote with an watery ink containing iron salts. The receiver decoded the message by painting the paper with sodium carbonate, a chemical cousin of baking soda.

Maintaining ink supplies was crucial during Washington's day. Now a trip to the grocery store will keep you well supplied.

3. Baking soda and grape juice
Make a paste of baking soda in water. Write your message with this paste on a piece of paper and let it dry. To decode the message, paint the paper with thawed grape juice concentrate. The acidic juice reacts with the basic baking soda and the purple grape juice turns gray. This worked best when I used plenty of baking soda paste and undiluted grape juice concentrate:

Writing in baking soda and developing with grape juice. Credit: Melissae Fellet

In the pictures above, you can tell that the paper has been altered because the paper buckles as the watery lemon juice or baking soda paste dries. Traditionally, writers would re-steam the paper to remove the bumps after scribbling a message with wet ink.

During the Cold War, invisible ink technology improved enough to remove the time-consuming steaming step. Soviet and East German spy agencies developed chemical-coated paper similar to carbon paper we use today. Agents sandwiched this coated paper between two blank pieces of paper. Writing on the top sheet transferred the chemicals from the middle sheet to the bottom paper.

Perhaps hacking an ink-jet printer to print lemon juice invisible ink would transfer your message without damaging the paper as well. I’d love to hear from someone who has tried this.

Have fun sending secret messages!

Chocolates for a blind taste test. Photo by Josh Weaver

Chocolate scientists study everything from the disease resistance of cacao trees to the health benefits of the finished product. But they shy away from one critical question: which chocolate tastes best?

Flavor is subjective, of course. But with a healthy sample size, a blind taste test, and a solid dose of statistics, one Bay Area foodie hopes to find an answer. IBM research engineer and UC Berkeley graduate student Christine Robson has held chocolate tastings at her San Jose home since 2007. This year's event on February 12 featured fifty-four chocolates, forty-two tasters, and an evening of rigorous data analysis.

Chocoholic scientist that I am, I couldn't stay away.

Guests included Annika Mongan of brand new Berkeley chocolate maker Ostara, who cleverly brought some raw material. Sure, I knew cocoa beans came from a cocoa pod, but I didn't realize they were surrounded inside that pod with gooey cocoa pulp, called baba in Spanish–drool. Despite its unappetizing name, I enjoyed the dried baba; its flavor was similar to other tropical fruits like papaya and mango.

Although most of us never taste it, cocoa pulp is crucial to the flavor of chocolate. After picking the pods, farmers pile the beans and pulp together and ferment them for days. Yeast, bacteria, and fungi take turns breaking down pulp sugars, producing acids. Longer fermentation creates more acidic beans and a stronger, more aromatic flavor. Shorter fermentation leads to a milder flavor.

When cocoa beans become raw chocolate, the process of fermentation is mostly responsible for the taste–with contributions from cocoa genetics and growing conditions. Some people swear by it. I fell in love with the rich, fruity flavor of raw chocolate at the Snake & Butterfly booth in the Campbell Farmers' Market. This five-year-old local chocolate company was named after Aztec gods to honor the food’s mesoamerican origins. Like Ostara, Snake & Butterfly started with raw chocolate, but decided after a couple of years to start roasting.

Roasting takes two fermentation products–amino acids and reducing sugars–and gives them a chemical shake called the Maillard reaction, which is famous among food scientists for browning bread and onions (among many other things). Along with fermentation, roasting produces the taste we recognize as distinctly chocolate.

Snake & Butterfly now only makes raw chocolate for special orders, but you can buy their roasted chocolate at Whole Foods, local farmers' markets, cafes, wineries—and art museums! Designer chocolate bars made to match the paintings of artist Jeremy Gilbert-Rolfe will be boxed up and sold at his exhibitions.

Ostara's raw chocolate will soon be on the shelves at Whole Foods as well.

If you’d like to see how Bay Area chocolate measures up against chocolate from around the world, check out Robson’s chocolate statistics. But be warned: chocolate snobbery is a slippery slope. According to Snake & Butterfly’s Celeste Flores, “My five-year-old refuses to trick-or-treat, because he says it doesn’t taste like chocolate.”

Photo by Sarah Deragon, PortraitsToThePeople

I am lucky enough to live in Hayes Valley, I’ve been living here for about four years now and have been privy to great community engagement; especially around the park at Hayes and Octavia. There is such a diversity of people that congregate in the park and one of the new neighbors has definitely added to the charm of the environs – Smitten Ice Cream.

The first flavor I tried was salted caramel, and it was hands down the best ice cream I had ever tasted. Since then, when I have guests visiting, I make sure that one of the local stops is Smitten. The ice cream is made to order only using the freshest local ingredients and it is frozen within 60 seconds using liquid nitrogen with a freezing point of -321 degrees F or 76 degrees Kelvin giving it a unique texture.

I heard Robyn Sue Goldman, owner of Smitten and Cory Bloome, the engineer responsible for fine tuning Robyn’s first prototype to mix the ice cream, speak about Smitten on Wednesday, January 18th at Nerd Nite. Smitten’s story from wagon to the Hayes Valley location is a great blend of quality and innovation. Robyn’s initial vision with Smitten was to get closer to the cow. With traditional ice cream that is frozen with conventional techniques, the texture is often stabilized with additives, emulsifiers or preservatives which mask natural ingredients. Old-fashioned ice cream in contrast has a few simple ingredients but takes quite some time to freeze. Introducing liquid nitrogen enabled Robyn to create ice cream the old fashioned way without the wait time.

The first ice cream machine was created and tested by Robyn through trial and error over many years. One of the major hurdles was to create a mixing apparatus that could properly and consistently mix the ice cream, without over-freezing or under-freezing any portion of it, which is easy to do with liquid nitrogen. She developed and later patented her creation of two swirling mixing arms with a helix design. She named the unique, patented mixer "Kelvin," giving tribute to the measurement of intense cold. Kelvin’s design, with the help of liquid nitrogen, creates a lower ice cream-freezing temperature while perfecting the mixing technique, resulting in the formation of smaller ice crystals in the finished product. These exceptionally small ice crystals are the reason why Smitten Ice Cream is so intensely creamy. To test her invention, Robyn initially hit the streets of San Francisco with Kelvin strapped on top of a Radio Flyer wagon and made incredible ice cream to-order. Popularity for Smitten Ice Cream grew, and the need for a store became tangible.

Before a store could be created, Kelvin needed to be refurbished and approved by UL, the regulatory agent. That is where Cory Bloome came in, affectionately dubbed “The Kelvin Doctor. Cory was the engineer who took Robyn’s prototype and list of improvements and fabricated the next generation of Kelvin’s for the store.

The four Kelvins are now busy mixing at the Smitten storefront at 432 Octavia St. (@ Linden St.). Try it for yourself if you find yourself in the neighborhood. Ice cream is served each day starting at noon. Monday through Thursday and Sunday, the ice cream is put away at 9pm; yet, Friday and Saturday you can come as late as 10pm for your fix.