If you live in a place with lots of people, decent internet, and maybe a 7/11 within walking distance, then you're probably used to getting your food in certain familiar forms. Like this, or this, or maybe this. Fewer and fewer of us these days get our sustenance in ways that most of us would consider natural, right off the branch, or off the bone. Instead, especially in industrialized countries, a lot of our food is processed, far away from where we actually eat it. So, we've had to devise all kinds of clever ways to make our food taste the way it's supposed to taste, and look the way we expect it to look, and generally survive the journey to our tables intact.

For about 150 years, the science of food chemistry has given us things like strawberry candy that's the color of strawberries, and soy-based burger substitutes that look and taste like meat instead of the mashed up edamame that they basically are. Plus, food chemistry has given us many different ways to preserve foods, protecting us from the toxic fungi and bacteria that try to get to our meals before we do.

Chemists accomplished all of these feats with the use of additives - substances that are used to affect any number of a food's characteristics, from their color, to their purity, to their "mouth feel." You've probably seen these additives listed on nutrition labels. Some additives are completely synthetic, made by chemists from scratch, while others occur naturally, though you might be surprised by how they're grown and harvested. And, maybe you're weary of having some of these compounds in your food, which is understandable, since none of us really knows what this means. But for whatever it's worth to you, all of the 3000+ additives found in food in the US, are listed by the Food and Drug Administration as GRAS, or Generally Recognized As Safe.

(01:38) Now, the most common kinds of additives, artificial flavorings, are really their own branch of food science. In order to answer questions like: why there's really no such things as nacho cheese, or why grape-flavored stuff never actually tastes like grapes, we'd have to get into the chemistry of taste. How the chemical receptors in your nose and mouth work, and how we can fool them. But, let's save that for another time.

For now, a lot of how food tastes, is informed by how it looks. So let's start with the most widely used food coloring in the world - red dye number 40, known in Europe as E129. People in the food industry like to refer to this particular compound as "Allura Red", which makes it sound like some kind of sexy nail polish, but considering the *this* is its full chemical name, I can't say that I blame them. Red dye number 40 is actually made from petroleum, and it's a kind of synthetic azo dye, a compound that contains azo bonds, double bonds that form between 2 atoms of nitrogen. These bonds give the molecule a particular shape that reflects light from the orange to red part of the spectrum.

But you might be thinking, there's a lot of food that's naturally red, like red cabbage, and beets. So why not just use whatever makes those things red, and put that in your strawberry candy. Well, those foods get their color from compounds called carotenoids, and they are sometimes used as food coloring. But carotenoids have a totally different structure than azo dyes do. They're basically long chains of carbon and hydrogen, and they break down pretty easily, especially when exposed to light and oxygen. So, many food chemists used red dye number 40 because it's not only cheaper to make from scratch than it is to extract carotenoids from other food, but the color also lasts longer on the shelf. Now, whether your food looks like what it tastes like, is one thing. But what about how it feels. 

(03:06) The consistency of food is important. People don't usually want to eat cheese that's runny or chew on jerky that's hard as a rock but consistency is one of the harder qualities of food to control. That's because the components of food products can often separate, like in salad dressings or sauces. And in other times, manufacturers want to avoid using certain ingredients, like animal fat, or egg yolk, usually to save some calories. So they need something to put in place of those ingredient to help hold the food together. And that, is where stabilizers come in. 

Stabilizers are compounds that chemically imitate fats, carbohydrates, or proteins to create homogeneous mixtures of ingredients that otherwise wouldn't stay mixed. It's thanks to stabilizers that veggie burgers feel like hamburgers when you eat them, and why pasta sauces pour out of the jar as a single liquid instead of separate globs of oils, water, and vegetable puree. And, two of the most common stabilizers are naturally occurring, though they're not from the sources that you might expect.

Xanthan gum might sound like something you'd chew during algebra class, but it's not what the name suggests. Chewing gum, like other true gums, is derived from plants. But Xanthan gum is produced by bacteria which release it as a waste product during fermentation. Manufacturers basically farm the stuff by keeping a bunch of bacteria known as Xanthomonas campestris in an oxygen-free environment. As the germs respire, they secret long complex sugars called polysaccharides which are then mixed with rubbing alcohol to get rid of the other waste, then they're dried and ground into a fine powder. This powdered starch is great  at stabilizing food, because it easily absorbs water. Molecules of xanthan gum attract molecules of water, which bind to it, creating a thick, gel-like substance. And this gooey medium is perfect for enhancing what food scientists call "mouth feel". 

So if you're making a burger out of soy beans or a salad dressing without oil, xanthan gum will fill in the spots where the fat used to be so your food feels like what your mouth is expecting. But hey, maybe you're not so keen on bacterial excrement. Maybe you'd prefer seaweed. Another one of the most commonly-used stabilizers in food is carrageenan, which is basically just ground-up red seaweed, a type of algae. Like xanthan gum, carrageenan is a long, complex polysaccharide and its curvy, helical structure makes it particularly good at binding not only with water, but also with proteins. This makes carrageenan a useful fat replacer in foods like ice creams, soy and almond milk, fake meats, and other foods where proteins make up the bulk of the dish. And it too is farmed on an industrial scale. Manufacturers just grow giant pools of red algae where they wash boil and dry it until all that's left is the carrageenan starch which is ground into flour. 

So not all food additives are synthetic and this is also true fr some of the most common preservatives - the chemicals that keep microbes and fungi from causing food to decay. For example, one of the most widely used preservatives is citric acid, the same stuff that makes lemons sour and oranges tangy. Citric acid is used to keep fruits from turning brown and canned foods from tasting canny, for the very same reason that it has a tart taste - it's acidity. In fruits and vegetables, citric acid blocks the natural enzymes found in plant tissues that cause them to spoil.

The enzyme phenolase, for example, it what makes a slice of apple turn brown. Phenolase uses oxygen in the air to create a brown pigment called melanin, which serves as sort of a protective coating over the apple's damaged tissue. But citric acid lowers the pH in that tissue which makes the enzyme unable to function, and when phenolase is prevented from making a brown mush, fruits and vegetables can stay fresh longer, even if they've been sliced or if they get damaged during shipping. Citric acid also has the extra benefit of bonding easily with free-floating ions of metal, so it and other acids are often added to canned foods. That way, any stray atoms of metal from the can will bind to the citric acid and not to the food inside, a process known as chelation.

So since citric acid occurs in lemons, oranges and anything else citrusy, making it must be easy. Just squeeze a bunch of fruit and ship it out to the ole food factory. Except... not really. The fact is there are literally not enough lemons and limes in the world to produce all of the citric acid that food manufacturers need, and extracting the acid from fruit is actually really complicated and expensive. So citric acid is mass-produced much like xanthan gum and carrageenan are, but instead of being pooped out by bacteria or mulched out of seaweed, it's excreted by mold. A black fungus known as aspergillus, which ironically enough is the same stuff that grows on spoiled food, produces citric acid when it metabolizes sugar in a low-oxygen environment. So food companies just spread out a bunch of the fungus on a bed of molasses and let it ferment. As the mold metabolizes the sugar, the citric acid is captured and dried into a powder. But the chemistry is a little bit different when it comes to what's probably the world's most commonly-used preservative: sodium benzoate.

The active ingredient here is really benzoic acid, a naturally-occurring acid that's found in things like plums and cranberries. In large-enough amounts, benzoic acid can kill fungi like yeast, and many kinds of bacteria by blocking the enzymes that they need to survive. So it's really handy for preserving foods that are already a bit acidic on their own like sauces, dressings, juices, jellies, and condiments. But benzoic acid doesn't dissolve in water, so food chemists have to stash it inside something that does. So they make a salt of benzoic acid by reacting it with sodium hydroxide -- also known as lye or caustic soda -- to make sodium benzoate. Now that's not something that occurs naturally, and some consumers are very wary of sodium benzoate and other compounds like it for that reason.

There's no denying that additives can have their downsides. Sodium benzoate, for example, has been found to react with ascorbic acid -- also known as vitamin C -- to produce benzene, a hydrocarbon that's known to cause cancer. In a random sample of 200 kinds of soft drinks sold around the U.S. from 2005 to 2006, the food and drug administration found that nine of the soft-drink brands contained levels of benzene that were above the federal safety threshold, of 5 parts per billion. It's worth noting that all of these drinks have since been reformulated. But some naturally-occurring compounds have been restricted too. The FDA has warned against using some baby food supplements that contain xanthan gum for instance because that might lead to potentially dangerous clumping in babies' intestines. As for red dye number 40, it's been used in the U.S. for more than 40 years, but it's banned in four European countries because some studies suggest that there's a link between the dye and hyperactivity in children, a link that the EU and FDA haven't established in their own research. 

So, if you live in a world where your food looks like this, then odds are there's seaweed in your soy milk, and petroleum by-products in your candy. Thanks to food chemistry, your eyes, mouth, and stomach will never know the difference. 

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