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Soy sauce is a lot like wine. The longer it ages, the more interesting and complex its flavor. It can get deep, man.

As far as 2,500-year-old condiments go, there's nothing like it. But within the world of soy sauce, there's a lot of variation.

"In the old days, there used to be like three brands. Now it's like yogurt. There are 50 different ones. It's confusing," said Grace Young, the James Beard Award-winning cookbook author and stir-frying guru.

Complicating matters, Japanese soy sauce differs from Chinese soy sauce, there are light and dark versions of each, and recipes that call for soy sauce often don't specify anything beyond "soy sauce."

I spoke with Young and Helen Roberts, Kikkoman USA's culinary development and public relations manager, to sort out the mysteries and many distinctions of soy sauce.

  • 1. The Basics.

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    Soy sauce is a liquid made from soybeans, wheat, water and salt. Broadly speaking, it falls into two camps: naturally brewed or fermented, and chemically produced.

    Naturally brewed soy sauce is fermented for months or longer. "The best soy sauce is actually two years or older," Young said.

    Chemical or non-brewed soy sauce is produced quickly within days, a mixture of hydrolized soy protein and flavorings such as corn syrup and caramel.

    Naturally brewed soy sauce has an aroma and complexity of flavor. Industrial soy sauce is one-note—super salty.

  • 2. Japanese and Chinese.

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    Among brewed soy sauces, there's another split: the geographic style. While soy sauce styles vary among cuisines including Korean, Indonesian, Thai, Filipino, and more, the types you're most likely to find at US grocery stores are either Japanese or Chinese in origin and/or style.

    Japanese soy sauce, or shoyu, is brewed with roasted wheat. Chinese soy sauce, which traditionally left out the wheat, is nowadays brewed with wheat flour. In addition, Chinese sauce sometimes contains added sugar, according to Roberts.

    This difference in ingredients as well as brewing time gives Japanese soy sauce a slightly sweeter, rounder flavor and Chinese soy sauce a denser, saltier finish.

    Generally, Chinese sauce also tends to be much thicker and darker than the Japanese style. Young said an easy way to tell is by shaking the bottle.

    "With Chinese soy sauce, you'll see it coats the bottle," she said.

  • 3. Light and Dark.

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    There's a third distinction: light or dark. The difference is largely due to length of aging.

    Both Japanese and Chinese light soy sauces are thinner and lighter in color (relatively speaking) but more intense in flavor than their dark counterparts.

    Dark Chinese soy sauce, which is aged the longest, also tends to be sweeter due to the addition of molasses or another sweetener.

    And here's another wrinkle: Dark Japanese soy sauce is what's most available and used, even if the bottle isn't labeled as such, which it usually isn't, Roberts said. For example, Kikkoman's regular Traditionally Brewed Soy Sauce is a dark soy sauce.

    In Chinese cooking, it's the opposite: light soy sauce is more common. Bottles will indicate light—sometimes labeled "thin" or "superior"—or dark. The latter is reserved for stews or as a flavor booster or finisher in sauces, Young said.

  • 4. What is Tamari?

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    Tamari is a Japanese soy sauce brewed with soybeans and no wheat—but sometimes there is a trace amount. So, not all tamari is gluten free. Check the label to make sure.

    And not every bottle labeled “gluten free” is considered tamari. For instance, Kikkoman's gluten free soy sauce is made with soybeans and rice instead of wheat.

    Check out more must-know soy sauce facts.

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