Category Archives: Food

Don’t eat pufferfish

Nature is chock full of toxins. Toxins come from all five kingdoms of life — bacteria, fungi, protists, plants and animals. Although the toxins span a broad range of shapes, sizes, and potencies, they’re all produced for the same reason: warfare.

Toxins come in two main flavors: as proteins and as small organic molecules. The protein toxins are both big and small. The small organic molecule toxins are very small.

What’s a small organic molecule? You probably know it as a (prescription) drug. Check out the image below:

A dizzying array of small organic molecules.

This image is a compilation of pills your doctor prescribes to treat a variety of ailments. Inside each colorful little package is one type of small organic molecule.

So a toxin can take drug form or protein form, both of which can enter your body and reek havoc.

The tropical pufferfish, especially prevalent in Japan, carries a small organic molecule toxin — the very small drug kind.

Here’s an adorable, cuddly pufferfish:

Source: Steven Hunt/Getty Images

The drug-like toxin found in pufferfish is called tetrodotoxin. An interesting little technicality is: the pufferfish itself does not make the toxin, but rather bacteria living inside the pufferfish produce it!

Tetrodotoxin is one of the most potent toxins out there. If you eat the equivalent of a grain of salt, you’re a goner. One tenth of that has the same result. One hundredth of that: same result.

Tetrodotoxin affects a cell’s sodium channel. If you haven’t read my last post, “Your potassium channel,” now would be the time.

The sodium channel has the same functionality as the potassium channel. The difference is only the type of stuff the channel flushes out and takes in. For a potassium channel, the type of stuff is potassium. For a sodium channel, the type of stuff is sodium.

We’ve learned that we don’t want to mess with these channels, because messing with the channels inhibits the cells from communicating with each other. And, just like with potassium, cells use sodium to talk. For example:

    Cell 1: “Hey, did you see the latest episode of ‘Glee?’”
    Cell 2: “Yeah, those New Horizons kids totally nailed it!”

I jest. Cells don’t talk about “Glee.” (Although they should.)

Most toxins affect the cells of the nervous system. So the type of cell that’s of interest here is the nerve cell. On a normal day, the nerve cell opens and closes its sodium channel, flushing out sodium, taking in sodium, all the while transmitting electrical signals to its neighbor cells.

Let’s say I have a hankering for pufferfish. I eat one. I now have tetrodotoxin loose inside my body. The very, very tiny tetrodotoxin finds its way to the sodium channels in my nerve cells.

A tetrodotoxin molecule plops itself down in a channel’s opening. That channel can no longer open or close. The sodium inside the cell cannot get out. The sodium outside the cell cannot get in.

Now that poor nerve cell can’t communicate; it has lost its ability to regulate itself. It dies. The cells around it die, too. Soon, enough cells have died that I’m paralyzed. Oops.

Another toxin that plugs a cell’s sodium channel is called batrachotoxin. This drug-like toxin is produced by the poison dart frog. How cute is this little guy?

A yellow poison dart frog. More than a hundred kinds exist -- all beautiful. Click the frog to learn more.

Besides sodium channel toxins, nature has potassium and calcium channel toxins, too. Scorpions, for example, produce protein toxins targeting the potassium channel of a nerve cell. Whew. I’d hate for the poor sodium channel to be singled out for destruction.

The black mamba snake, the largest venomous snake in Africa, produces a large protein toxin called calciseptine. Calciseptine targets the calcium channel, as you may have guessed from its similar name. This particular toxin is such effective warfare that the black mamba snake eats like a king.

Here’s a black mamba snake eating some unfortunate rodent:

Yummy! Click on me!

Don’t eat black mamba snakes. Also, don’t eat scorpions. Also, don’t. eat. pufferfish.


Technology at Fort Bliss

If you read my last post “Chemical weapons and clay,” you’ll know that I enjoyed a brief stint as a policy fellow at the National Academy of Sciences. Twelve weeks serving on the Board on Army Science and Technology (BAST) did wonders for my knowledge of the U.S. Army. Granted, the bar was, ahem, low.

Further into the fellowship (I believe we’re in week 5 here) I traveled with two other BAST staff members to Fort Bliss. One might imagine that Fort Bliss is in an exotic location, perhaps a beautiful island in the Pacific Ocean. Nope. Fort Bliss is in El Paso, Texas.

El Paso sits on Texas’ western border, less than 20 miles from Juarez, Mexico. Juarez…it sounded familiar to me but I couldn’t place it. A quick call to my mother went something like this:

    Sarah: “Hey Mom, what’s Juarez all about?”
    Mom: “JUAREZ MEXICO? Oh my God, Sarah, do NOT cross that border. Do you even have your passport? It doesn’t matter. I don’t care. Do NOT leave Texas while you’re at that army conference.”

Juarez, as it turns out, is infamous for crime, violence and drugs. Hmmmm…let’s put an army base beside it and name the base Fort Bliss! I give the U.S. Army a gold star sticker for nomenclature (this means “naming”) humor here.

One aim of the Fort Bliss BAST meeting focused on learning about new technology. A significant portion of the money annually dolled out to the Department of Defense funds army research and development, i.e. army science and technology. Just like in a university or at a private company, scores of scientists and engineers conduct basic and applied research under the auspices of the Department of Defense.

At Fort Bliss I watched soldiers plow through computer-based training modules, fighting virtual enemies of all shapes and sizes. Soldiers spend several weeks on a team, sitting together in one room, gazing up at a huge screen that depicts their battlefield. The soldiers advance their skills and knowledge, stage by stage, until their virtual training is complete.

Besides time spent on the main army base, we visited soldiers in the field at their training site, located an hour away near the base of the mountains. At the training site I had a crash course in unmanned aerial and ground systems, robots, monitoring devices, and practice attack strategies.

After one morning out in the field we broke for lunch. One dozen soldiers had just finished a practice attack, complete with green smoke bombs as diversions. Let’s just say that if I had a do-over, I would spend less time watching the green smoke spread slowly across my field of vision and more time tracking the attacking soldiers.

Where did those pesky attackers go? Oooooo pretty green smoke....

For lunch we ate soldier food: Meals, Ready-to-Eat, or MREs. An MRE comes in a thick, brown plastic wrapping that you open with your army knife or whatever weapon(s) you have on hand. I met a soldier from my hometown of Cary, North Carolina, who opened my MRE and gave me an extra for the road. I love Southern hospitality.

Decked out in a parka, I pose with my new friend from Cary, NC.

An MRE is calorie-rich to keep a soldier well-nourished for battle. The calories, however, do not come from tasty food, but rather from strange food-like substances only identifiable from their labels. After eating one such meal, I was less excited by the Southern hospitality than I had initially been. Below is some of the “food” I got:

    Mushy greenish puree = pears
    Brown chunky liquid = beef stew
    Purple powder = grape juice
    Little white disc = gum

I was impressed by the army’s technological progress to integrate information for its soldiers. Theoretically, better technology leads to better-equipped soldiers, which, in turn, should result in more successful missions.

Soldiers will soon have (if they don’t already) a smart phone with databases of friendly and enemy faces, locations of safe and unsafe places, and GPS-style navigation capabilities. Imagine a map of the Afghani desert, complete with information on where to go, and, more importantly, where not to go.

The most enjoyable part of my trip was chatting with the BAST experts. These experts included retired military generals and majors, engineers of several types (no, not clay) and physicists. Those folks were chock full of information about military technology, so I networked my way through the group. Besides scoring business cards I reveled in the free drinks.

After returning to D.C. I wrote my new contacts thank-you notes, beefing up my D.C.-based contacts list to include DARPA (the Department of Defense’s innovative technology research arm) and the conservative think tank The Heritage Foundation. Will I ever work at DARPA or The Heritage Foundation? Likely not. But one can never have too many contacts. Mark my words!

The skinny on the bubbly

In the world of enology – the “ology” dealing with wine – sparkling wine is but a small portion of the world’s total wine production. The U.S. sells 150 million bottles annually, with France taking the lead at 500 million. A Wine Business Monthly article on how to make sparkling wine highlights some reasons why the business of sparkling wine is, and shall remain, a small percentage of the wine market.

Among the top reasons: the grapes must be of exceptional quality for a sparkling wine – bubbles intensify a wine’s flaws – and a second fermentation step takes extra time and money.

The seventeenth-century Benedictine monk Dom Pierre Pérignon is erroneously credited with inventing sparkling wine. If alive today, he would argue that bubbles are not meant for wine. Not so, argue many winemakers and wine drinkers today. Sparkling wine has recently surged in popularity, especially among younger drinkers.

According to a recent review article in the journal Trends in Food Science and Technology, our sparkling wine methods have not changed much since Pérignon’s time. Take a base wine, throw in some sugar and yeast, let it sit for a while, bottle it and allow it to pressurize, and presto – you’ve got sparkling wine.

How much sugar you add determines how sweet the sparkling wine is. On average:

    Brut is 1 % sugar
    Extra dry is 2 % sugar
    Sec is 6 % sugar
    Demi-sec is 10 % sugar

The basic technology of sparkling wine production involves two fermentation steps – one produces a base wine and the second yields the bubbly version. Traditionally, the second fermentation occurs directly in the bottle — no filtration, no transfer. The Italian Talento, the Spanish Cava, and, of course, the French Champagne, where sparkling wine was first developed, are made in this fashion.

The wine can be filtered and transferred to a new bottle post-fermentation, or, like the Italian red Lambrusco and white Asti, fermented in a hermetically sealed tank prior to bottling.

The second fermentation step produces the most important visual aspects of a sparkling wine — bubbles and foam. The bubbles and foam are affected by the wine’s chemical composition. This includes how much and what kinds of protein, sugar, fat and nucleic acids are present.

But how do these compounds get into the wine? The yeast do it through autolysis. Autolysis is just what it sounds like: auto (self) and lysis (breaking down). Yeast cells make alcohol out of sugar until they run out of food. Once their food is gone they break down, releasing enzymes that digest them and their nearby neighbors. Their cell walls fragment, and, no longer imprisoned, the proteins, sugar, fat, and nucleic acids can simply diffuse right out.

Proteins, the major compounds released into wine, are foamy; more protein in the wine means more foam. To counteract this, winemakers add stabilizers, which are salts like potassium sorbate, and clarifying agents, like the aluminum silicate compound bentonite.

Sugar comes from the grapes as well as the process of autolysis. The sugar of importance is called mannose, and more is better. Fat content affects foam levels, and nucleic acid content affects flavor.

Research on sparkling wine technology focuses on improving this second fermentation step, namely by speeding up the slow process of autolysis. The current tricks are to add aged lees (these are the dead yeast cells) to the wine and to increase the temperature during aging. Sounds simple, but these tricks affect the aroma and taste of the wine.

The most recent improvements to sparkling wine technology involve genetically engineered yeast strains. These strains are variations of the budding yeast Saccharomyces cerevisiae, which you know from drinking beer and/or eating bread. These same yeast are in wine, engineered by researchers to have improved fermentation abilities. They have enhanced autolysis capacity, better foaming capability, increased mannose release, and less aggregation.

Genetically engineered yeast strains are not yet approved for use in winemaking, but it’s only a matter of time before wine joins the list of genetically modified foods. In the meantime, pour yourself some champagne and enjoy the 20 million bubbles in your glass. After all, that’s 20 million more than Pérignon ever relished.

Glowing bananas

Bananas glow. It’s true and it’s all because of one molecule.

Source: Wiley InterScience (Copyright © 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Chlorophyll absorbs energy in the form of light and converts this energy into oxygen gas, providing us mammals with fresh air to breathe. The chlorophyll molecule is a large ring, with carbon, oxygen, hydrogen and nitrogen atoms (the four elements of life) bonding together in a variety of ways. Some of these atoms are hanging off the side, while others form the core of the ring. A magnesium atom plops itself right in the center.

Because chlorophyll absorbs either red light or blue light (the corresponding wavelengths are 665 nanometers and 465 nanometers), the pigment itself is green. Plants, which are chock full of the molecule, are thus green.

As plants age, their color fades. The green color disappears as the chlorophyll breaks down. This process of breaking down is called catabolism. The chlorophyll, because it is so large, forms smaller and smaller molecules as it breaks down. Scientists call these molecules chlorophyll catabolites.

The final products, called non-fluorescent chlorophyll catabolites, are found in aging plants, and scientists have recently discovered that they also exist in aging fruit. Dying plants and ripening fruits break down chlorophyll in the same way.

Why mention that these molecules are not fluorescent? Turns out that during chlorophyll catabolism, intermediate molecules are formed that are, in fact, fluorescent. As the fruit ripens, or ages, these fluorescent chlorophyll catabolites are released by the skins or peels. Normally, we look at our fruit under white light, within the visible spectrum, so we don’t see anything out of the ordinary. But shine UV light on a pile of ripe bananas and the banana peels glow blue.

A group of scientists in Austria studying aging and catabolism published this discovery last year. They exposed bananas of varying ripeness to UV light (wavelength of 350 nanometers) and observed the light that the bananas emitted. The underripe green bananas were barely observable, the ripe yellow bananas were blue, and the overripe brown bananas were, again, hard to observe.

These results showed the researchers that the fluorescent chlorophyll catabolite was an intermediate product. Moreover, it seems to be in bananas of just the right degree of ripeness. Here is a good summary of the article.

Two weeks ago a PNAS study by this research team showed that they can track these fluorescent chlorophyll catabolites as they appear and then disappear. These molecules serve as markers to track cell aging and death. The researchers state, “Thus, they [the fluorescent chlorophyll catabolites] allow for in vivo studies, which provide insights into critical stages preceding cell death.”

Here is a good summary of the article. Watching the fluorescence as it grows in and out reports on the aging process of the plant or fruit.

Take home message of these studies? Grab your black light next time you go to the grocery store and you’ll have a cart full of perfectly ripe fruit.