IRamen is a noodle soup dish that originally made its way from China to Japan when the country reopened its borders during the Meiji Restoration. The dish has been refined and improved to such an extent over the past century that it has almost overshadowed its original Chinese cousins on the world stage. The world of ramen is quite complicated and this article will systematically classify the different styles of ramen that are common in Japan along with their various soup flavors, broth types, meats, and accompanying toppings.
Shio Ramen . Shio means salt and this is traditionally how ramen soup is flavored. All Western broths would be considered to be of the Shio type. The salt does not alter the appearance of the broth and therefore the Shio soup tends to be light and limpid in color. Shio flavored soup will tend to be a little more salty than the other types.
Shoyu Ramen . Shoyu means soy sauce and this is the next oldest type of flavor. Instead of salt, a sauce obtained from the fermentation of soybeans is used to make the broth salty. This sauce is not your regular table soy sauce, but typically a special sauce with additional ingredients prepared according to a secret recipe. Broth for Shoyu is the only type that tends not to contain pork. Shoyu soup is also usually light, but it is dark in color and sweeter than Shio soup.
Miso Ramen . In more recent times, miso paste has also been used to give ramen broth its savory flavor. If miso is used, it is immediately evident as the soup will be opaque. Shio or Shoyu flavored soups just accentuate the flavor of the broth below, while miso leaves a fuller and more complex taste in the mouth as it also has a strong flavor.
Tonkotsu Ramen . Technically it's not a real flavor as it contains salt or soy sauce. It is made by boiling ground pork bones (ton = pork, kotsu = bones) for 12-15 hours until all the collagen has dissolved in the broth like jelly (details here). The result is a rich whitish soup distinct enough to consider Tonkotsu as a separate fourth flavor of Ramen. To be clear, the use of pork bones does not automatically mean that the soup is of the Tonkotsu type. If the pork bones are boiled whole for a relatively shorter period, the result is just normal pork broth.