Everything you ever needed to know about soy sauce
Anyone who likes Asian food probably buys soy sauce all the time. Maybe you just grab the cheapest bottle on the shelf, maybe you pop for the name brand because, hey, that's what they serve at restaurants, right? But is all soy sauce created equal? Is it vegan? Gluten-free?
So what the heck is soy sauce, anyway?
Soy sauce is a by-product of fermented soybeans and wheat with molds added to it (who knew mold could taste so good?). After the molds have grown, the entire concoction is brined in salt water for bacteria to break down the sugars. It's then fermented. The longer it ferments, the better. Most of what you'd consider "standard" supermarket brands are aged for only about six months, but higher-end brands are often aged for years.
There are also soy sauces made with acid-hydrolyzed soy protein instead of brewed, which take only a few days. They don't taste exactly like real soy sauce, but you've probably still had it in the cheap, little clear packets that come with your Chinese delivery.
Many people think of soy sauce as "Japanese salt," but it's much more than that. Soy sauce is a major source of umami. In fact, I often use it in non-Asian dishes, especially marinades, for that reason.
What about special dietary concerns?
In general, most soy sauce should be vegan. It's made with soybeans, sometimes wheat (depending on the type of soy sauce), water and salt. That said, you should check with the manufacturer to make absolutely certain it doesn't add anything during the process that would be considered non-vegan. Some companies use additives for sweetness or shelf life.
If you have celiac disease, know that most soy sauce isn't gluten-free (you should look for certified gluten-free or tamari, which is traditionally made with little or no wheat, but check the label). That said, many people on gluten-free diets do report they have no issues with soy sauce when used in small quantities because much of the gluten is eaten by the yeast during the fermentation process.
Many people mistakenly believe they should avoid soy sauce if they have an allergy to lactose, because the production of soy sauce generates lactic acid. But bear in mind lactic acid isn't the same thing as lactose, so you should be fine with soy sauce.
All soy sauces are high in sodium. You can buy reduced-sodium sauce, but that doesn't mean sodium-free. They still have between 9 and 13 percent sodium as a general rule. Don't confuse light soy sauce with low-sodium or make the mistake of thinking light soy sauce is better for you (see usukuchi below).
Types of soy sauce
Soy sauce is soy sauce is soy sauce, right? Nope. Soy sauce is made in a variety of Asian countries, and each country (and sometimes regions within those countries) has its own take. But there are a few main types we tend to see in the U.S.
Koikuchi — This is the soy sauce most of us are used to. It's what Kikkoman makes (at least its regular soy sauce) and is what 80 percent of Japanese people use. The word koikuchi means "dark mouth," and as its name implies, it's rich in flavor and dark in color.
Usukuchi — Another Japanese soy sauce, usukuchi is lighter in color than koikuchi. When you buy light (or lite) soy sauce, you're generally getting something at least intended to be more like usukuchi (though as stated previously, many soy sauces aren't brewed traditionally and may have additives). The reason you should be careful assuming this is better for you is because it's simply not. "Light" in this case simply refers to the color, and in fact, it's generally saltier. It's just a regional variation. Usukuchi should be added later in the cooking process to get the full benefit of its flavors.
Tamari — The new en vogue soy sauce (and my personal favorite), tamari is a thick, viscous soy sauce. While many think it's an entirely different product, this isn't the case. It's another regional variation of soy sauce, made with a fungus called, well, tamari. It has a reputation for being gluten-free, and it is usually at least mostly soybean, though wheat may also be used. As with all soy sauce, the yeast do eat most of the gluten, so whether you need to worry about it depends on the level of your sensitivity. That said, many tamari brands do brew without wheat at all. Tamari is most commonly used on sashimi.
Genen/teien — These are both names for low-sodium soy sauce, which is koikuchi that has had the salt content reduced (but not eliminated) after brewing.
How to buy soy sauce
As with all things, you get what you pay for. Which type of soy sauce you choose depends on what you're making and your personal preferences, but cheapo soy sauce (half of which is probably fake soy sauce anyway) isn't going to be fermented as long and isn't as flavorful.
First, buy the best kind you can afford. Don't be afraid to have more than one if you use it frequently or do a lot of marinating. The koikuchi (regular or low-sodium) is the most versatile, as it's what's called for in most recipes and what most of your guests would be used to. I like to keep a bottle of the (non-fake) cheap stuff around, though. I use the higher-quality stuff for dipping and cooking in small quantities, but if I have to make a marinade, I make it with half good stuff and half cheap stuff (unless I'm having company).
I tend to prefer koikuchi because it's not as salty and has a richer flavor, but the usukuchi has its merits too (especially in meat marinades). And I simply can't live without my tamari!