Question: Is there a difference between Chinese and Japanese soy sauce? And what about light and dark soy sauces?
Answer: According to Bruce Cost, author of "Bruce Cost's Asian Ingredients" (William Morrow & Co., 1988: $22.95), "The Chinese invented soy sauce, and the Japanese learned the technology from them.
"The Chinese, particularly in the south, use both light and dark soy sauce. The latter is aged longer, and toward the end of the processing is mixed with bead molasses, which gives it a darker, caramel-like hue. You can think of them as you would red and white wine, since as a rule, dark soy flavors (and colors) heartier dishes, particularly those with red meat, whereas light soy sauce is more appropriate with seafood, vegetables, soups and in dipping sauces. Traditional northern Chinese cooks use only dark soy sauce," says Cost.
He goes on to explain, "The art of making soy sauce was introduced to Japan by the Chinese about 1,000 years ago, and since that time the Japanese have developed distinguished varieties to meet the needs of their cuisine. Whether Japanese or Chinese, the aging and fermenting are the same, but as a rule, Japanese soy sauce (shoyu) contains more wheat and is thus a little sweeter and less salty. Standard to Japanese cooking is what they call 'dark' soy sauce, which is labeled simply 'soy sauce,' shoyu, or koi-kuchi shoyu. This sauce, on a Chinese scale of dark to light, would fall on the light end, and in a pinch could be substituted for Chinese light soy."