SOY sauce is a quintessential ingredient in Chinese kitchens, enhancing soups, stews and other dishes with a unique flavor that defines the cuisine.

Samuel Muston, food editor at The Independent Magazine, described soy sauce as “an eternal beacon, guiding troubled dishes into softer waters.” If he had to pick something to take to a desert island, it would be a “gargantuan bottle of soy sauce,” he said.

Most Chinese would agree with that praise.

“Soy sauce not only salts dishes, but it also give them flavor and color,” said Grace Wen, who lives in Shanghai and likes to cook at home. “It can turn simple ingredients into something very special and delicious.”

One of the oldest condiments in the world, soy sauce figures prominently in many Asian cuisines. In Chinese, it’s called jiang you, which translates as “sauce oil.”

In ancient times, this preserved seasoning was brewed from fresh meat, similar to today’s fish sauce, and it was used exclusively for the imperial court. The condiment expanded to the general public when soybeans were found to produce a similar flavor at a much cheaper cost.

In the Song Dynasty (AD 960–1279), soy sauce was mentioned in several books. The folk recipe book Wu Shi Zhong Kui Lu, compiled by a woman surnamed Wu, featured a steamed crab dish that called for wine, soy sauce and sesame oil as seasonings.

Soy sauce was introduced to neighboring countries in Asia by Buddhist monks. Japan, Korea and Southeast Asian countries went on to develop their own versions of soy sauce.

The magic of soy sauce has spread to Western recipe books. Common salad dressings, like honey mustard, often call for a few drops of light soy sauce to boost the flavor. And bottles of soy sauce often sit in the condiment tray on restaurant tables.

Making soy sauce is a bit of an art. That’s why there are so many different varieties on supermarket shelves. One of the most common brands in the West is Japan-made Kikkoman all-purpose soy sauce. China’s Pearl River Bridge superior light soy sauce is also widespread.

Though soy sauce is rich in amino acids and packs a great amount of antioxidants that are quite beneficial to health, the sodium levels in the very salty condiment are also very high. Today, many soy sauce manufacturers produce reduced-salt versions.

In China, soy sauce is divided into two main categories: shengchou, or fresh soy sauce, and laochou, or dark soy sauce.

Fresh soy sauce is light and aromatic, with a hint of sweetness. It’s often used to make cold salad dishes, dipping sauces or as soup seasoning. High quality fresh soy sauce can give simple vegetable dishes an umami, or glutamate, taste.

Dark soy sauce is used to add color to stews, stir-fries, and braised and roasted dishes. It is not necessarily saltier, though it is fermented for a longer period of time than light soy sauce and sugar is often added to give it a sweeter taste.

Chua Lam, the famous gastronomist, food critic and television host, wrote that the soy sauce produced by Kowloon Soy Company represents the soul of Hong Kong, with its very rich, thick and sweet texture.

There are two common blended soy sauces in China. The mushroom dark soy sauce adds straw mushroom broth in the aging process for a richer flavor. It is used in the same way as common dark soy sauces in cooking.

The Suzhou-style shrimp soy sauce is a light variety brewed with fresh shrimp and seasoned with sugar, white spirits, ginger and spices. It is used as dressing or dipping sauce.

Jiang you gao, or soy sauce paste, is a solid form that originated in the Yulin region of Guangxi Province. The locals there traditionally seasoned stir-fried pork slices with the paste, though it’s now harder to find because liquid versions are so much more popular.

In Shanghai, there is a local seasoning sauce called la jiang you, which translates as “spicy soy sauce.” For the Shanghainese, la jiang you is the soulmate of deep-fried pork chops. But despite the name, it has nothing to do with common soy sauce. It’s actually a Worcestershire sauce from 19th century England that was so named because of its resemblance to traditional Chinese dark soy sauce.

In the popular Japanese TV series “Shinya Shokudo” (Midnight Diner), adapted from the manga series by Yaro Abe, one episode featured a dish called butter rice. It was cooked with only three ingredients: rice, butter and soy sauce.

The dish was made by placing a small cube of butter atop a bowl of hot cooked rice. When the butter melted, soy sauce was drizzled over it. Voilà! Comfort food, quick and easy.

The episode used the famous Kikkoman soy sauce, made by the Noda, Japan-based company founded in 1917. Kikkoman has production plants in China, the United States, the Netherlands, Singapore and Canada. The iconic bottle with a red cap was designed by Kenji Ekuan.

Soy sauce is called shoyu in Japanese, and there are several different types of soy sauces, including the most common koikuchi-shoyu, usukuchi-shoyu and tamari-shoyu.

Kikkoman soy sauce is the koikuchi-shoyu variety, which is somewhat thicker than usukuchi-shoyu.

Because koikuchi-shoyu is brewed with soybeans and wheat, it is clearer and thinner than Chinese soy sauces produced only from soybeans. It also has a sweeter taste.

Tamari-shoyu is more similar to the traditional Chinese dark soy sauce and contains little or no wheat.

The Japanese grade soy sauces in three official levels, based on the nitrogen content. The highest grade, tokkyu, contains more than 1.5 percent nitrogen.

Other Asian countries also have their own soy sauces. In Indonesia, it’s the molasses-like kecap manis, a sweet sauce fermented with soybeans and flavored with generous amounts of palm sugar. It’s often used in satay dishes.

It’s all a bit confusing when you want to buy some soy sauce in the supermarket. On Chinese shelves, there are rows and rows of different types and brands.

For light soy sauce, the top three choices are Lee Kum Kee salt reduced light soy sauce (8.5 yuan (US$1.3 for a 500ml bottle). It’s produced by a Hong Kong-based company. Or you might try Shinho June premium soy sauce (at 11 yuan) or Haitian’s gold label premium light soy sauce (at 7 yuan).

Hoda Organic has a reduced sodium light soy sauce for babies, though it comes with at a pricey 30 yuan for small 160ml bottle. No matter which soy sauce you choose, it’s best to feed it sparingly to children because of the salt content.

For dark soy sauce, try Lee Kum Kee selected dark soy sauce (at 10.4 yuan per bottle) or Haitian mushroom dark soy sauce (at 8 yuan).

In the Japanese food aisle, there are various soy sauces for sashimi, sushi and other dishes.

Kikkoman soy sauce sells for about 23 yuan for a 150ml bottle.

Though soy sauce has a long shelf life, it’s still essential to keep the bottles tightly capped when not in use and to store them at room temperature.