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Wednesday, April 16, 2014

Protein



Protein. 

When it comes to food, you see that word thrown around in so many different contexts. Recent news talk about too much protein being as bad as smoking. Menus and TV shows casually reference the "protein" to be used as an ingredient for a dish or a meal. Then there are the now ubiquitous shaker bottles and a whole industry of "healthy" protein supplements for body builders. Even snack bars worry about their protein content.

So, do you know what protein is? If you want to, you can go back to the post where I explained what carbohydrates are. Spoiler alert: proteins are also chemicals.

Now that that is out of the way, if we think of  chemistry of life as a band, proteins are sort of the front man. Although the other compounds — carbohydrates, lipids, nucleic acids — all have their roles to play, proteins tend get a lot of the limelight. In raw chemical composition, proteins are pretty similar to carbohydrates - made up of carbon, hydrogen, oxygen (plus some nitrogen — that last bit isn't present in carbohydrates).  But in biochemistry, composition isn't all - the arrangement of the atoms can make dramatically different molecules.

Proteins are made from smaller units called amino acids. You'll hear this mentioned in various food products and supplements, but few people actually explain what they are. The name tells you a bit about them - it's a molecule with an amino (this is where the nitrogen goes) end and an organic acid end. What matters is that an amino end can connect to the organic acid end of another amino acid, a brief reaction happens, and the two can be linked up to form a new, bigger molecule. The linkage formed is called a peptide bond, thus, short proteins are often called peptides. Note that the new peptide still has an amino end and an organic acid end - the chain can be extended almost indefinitely as long as those two ends can form new peptide bonds.

Glutamic acid (aka glutamate) from Wikimedia Commons

Well, that's just the ends. In the middle, that's where the variation happens. Different atoms can hang off the middle part of an amino acid, resulting in a wide array of different compounds. For biological purposes, most proteins are made from just 20 kinds of amino acids strung together in various combinations. Some of these amino acids by themselves are well known - perhaps the best known is glutamate, the active component of MSG.

But you'll also often hear the term "essential amino acids". Human physiology can actually build amino acids from even smaller components, or convert them from other molecules, but there is a subset of these amino acids that can't be formed this way. We have to procure them from diet, making them "essential" to include for nutrition.

So, what do proteins do? Just like using a small set of letters, one can write a poem, a novel, a computer program, a recipe or gibberish, the set of amino acids can be linked together to form proteins that catalyze chemical reactions (enzymes), build structures like skin or hair, keep cells transparent to focus light, hook up together to move bones or heart (and consequently cars and airplanes), fold and fabricate other proteins, and all the wondrous activities of life itself. What we seek when we eat are to break down the proteins in other organisms (and yes, plants have protein, too), to salvage the pieces that our bodies can't make. 

Monday, March 31, 2014

Disease, Cartels, and A Cultural Crop

For all the hullabaloo about "gourmet" food trucks and park devoted to them, rolling taquerias have been a mainstay in Houston dining - in these loncheras,  tacos come fast, flavorful and cheap, unceremoniously plopped onto the cheapest disposable plates, to be eaten while standing under the sun.

But on a recent trip to an Airline taco truck, I noticed a disturbing trend.
Note the yellowish tinge to the obligatory slice of lime. 

The tell tale seeds confirmed my suspicion: they are distributing lemons.
Surely, the Texas dining scene will not be unscathed by the sudden quadrupling of lime prices in recent weeks. Multiple factors are at play from politics to plant disease, but since Mexico provides 95% of the lime supplies in North America, this ubiquitous fruit, previously so plentiful as to be given away (and optionally discarded) is now becoming a pretty precious commodity. Hoard your lime juice, or be prepared to explore other citrus flavors. 

Thursday, March 27, 2014

Food blog stereotypes

I'm straying from the science a bit to post an observational piece. Here are the top 5 food blog post stereotypes:

5. Food porn articles. You know, those things that highlight pictures and videos of food as intimately as hard core porn can be. They are there to titillate your imagination. The stock in trade here is jealousy - so dining in fancy restaurants slides in there.


4. Recipe articles. Often tired rehashing of old ideas, maybe given a "healthy" twist. Not that the latter is really scientifically provable.

3. Disgust response articles. These are closely related to chemophobia articles, which basically fan ignorance to promote nonsensical memes. They can be made to sound outrageous, but if you look a little deeper, with the lens of science, it's much ado about nothing.

2. "Science-y" articles. These ones pop up every so often, written with little more than a casual reference to Wikipedia, or maybe some stray sensationalized article in the back section of a larger news site. They'll use the science-y buzzwords, but are the truthiness of the online food world. And are often so wrong, but vigorously defended.

And the No 1 stereotype....

1. Listicles.

Just don't.

Monday, March 10, 2014

The benefit of enzymes


Peeling fruit can be a laborious and painstaking task, specially if the fruit is particularly small. Fortunately, in the case of citrus, this can be accomplished by a technique called enzymatic peeling. Basically, pectin is a complex carbohydrate that is the major component of the white part of the citrus — the albedo or "pith" —and by introducing an enzyme called pectinase (various commercial food grade versions of this exist) through little holes in the rind, the pectin is digested away, leaving beautifully peeled citrus fruit. You'll have to see the pictures, which, incidentally, also leave the rind largely intact.


Then again, the act of peeling small animals, particularly vertebrates like birds or rodents, can also be laborious. Can we bring the benefits of enzymatic peeling to animal butchery? To do this, we need to understand a little bit about animal anatomy and tissue structure. Between bundles of muscle, and attaching it to the skin are the tough connective tissue collectively called the fascia. Sometimes, bacteria or other microbes can infect the fascia, resulting in its degradation - a condition called necrotizing fasciitis. More commonly, it's called the "flesh eating bacteria syndrome", because the flesh falls apart as the fascia is degraded. One of the enzymes thought be responsible is called hyaluronidase, which degrades the carbohydrate hyaluronic acid, a major component of the extracellular matrix of the fascia. Hypothetically, one can inject an animal corpse with commercial food grade hyalorunidase, and given enough time, the fascia will break down, and you can simply slip the skin off.

As a side note, hyalorunic acid serves diverse roles in a vertebrate body, from providing suppleness in skin (hence its popularity as an ingredient in many cosmetic products) to the resiliency of joints. But it also serves an important role in cancer development and prevention. The naked mole rat is the only mammal known to be immune to cancer, and it turns out that this is linked to their ability to produce a lot of hyaluronic acid. But that is also why they look the way they do - very wrinkly.

Wednesday, March 5, 2014

Do you even science?

The cheeseburger/salad low carb thing at The Counter in San Diego. It isn't particularly a well designed expedient. It was pretty bad. 
It doesn't take much to search out the term "I am not a science experiment" to bring up numerous images of fear mongering rallies against genetically modified organisms in food. This insinuation of nefarious experimentation is a common bromide meant to stir up conspiracy, suspicion and fear, but in reality is of course completely unfounded. But it works, in part, due to the casual way people use the word "experiment".

Often, for example, as people try things out in the kitchen, when they deviate from recipes and convention, they call that "experimenting" with the food. In fact, just bringing in anything unfamiliar, such as trying to cook the cuisine of a different culture, can be called experimentation. But in science,  "experiment" is a precise and vital function in the process.

The experiment is the process in which one tests a hypothesis. In short, one should begin with a question, and the experiment should be designed to answer that question. A well designed experiment will take as many variables as possible into consideration, and will minimize ambiguity in the result. It has a definite beginning and an ending, and at the conclusion will arrive at an explanation for the question it begins with. To do this, at least two requirements are employed: controls and replication. Controls are set isolate the question being tested from other variables. For example, if you are testing that adding extra eggs to a recipe to see if it increases tenderness, then you must also perform the same recipe without the additional eggs to compare. Ideally, a control should be performed in the same time frame.

In addition, replication is needed to ensure that against the potential for error. After all, if we have learned something, it should have predictive value, and can be repeated. This is why when someone reports testing out a new diet as "feeling better", it isn't scientifically valid. This is testimonial anecdote, and is poorly repeatable - and thus, the lowest form of scientific evidence. Even though this seems to be the form people instinctively trust - and marketers exploit it with gusto.

So, the next time someone talks about being a science experiment - or experimenting with their food - ask about the hypothesis, controls and replication. Because without those, well, it really isn't an experiment.

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