Sweet soy sauce is a type of sauce made from soy, salt, sugar, water and sometimes wheat, spices or herbs. It is commonly used in cuisines from South-Eastern Asian nations, such as Thailand and Indonesia. In order to make this type of sauce, sugar is added to regular soy sauce after it has fermented.
The main ingredients in sweet soy sauce are soy sauce and sugar. Though there are a few different ways to make soy sauce, most are made by fermenting soy beans in salt water brine. Often, a grain, such as wheat or rice, is added to the soy to help with the fermentation process, but there are some types of soy sauce, such as tamari, that do not make use of any grains. The sauce ferments over the course of a few months, during which time different yeast and bacterial cultures grow in it, each of which consumes a different substance, such as lactose or sugar, and secretes a different by-product into the sauce, such as lactic acid or alcohol. Any of these types of soy based sauces can be used as the foundation for a sweet soy sauce.
Though it is possible to add sugar to a soy sauce while it is fermenting, this sugar will be eaten by yeast and turned into alcohol. Sugar is usually added to the soy sauce once the fermentation process is complete. In order to incorporate sugar into the sauce, both the sugar and the soy sauce are heated and stirred together until the sugar is completely dissolved. Unlike the process by which salt is diffused into water, sugar molecules are broken down in the liquid and will not condense into sugar crystals as the sauce sits. The sweetness of this type of sauce can be controlled by adding more or less sugar, with most recipes calling for somewhere around a one to one sugar to soy sauce ratio.
It is also possible to flavor sweet soy sauce with herbs or spices. In Indonesian sweet soy sauce, which is called kecap manis, garlic and star anise are infused into the sauce. Curry leaves, ginger, and hot peppers can also be placed in sweet of soy sauce. Once the sauce is ready, it can be used on noodles, vegetables, meats and rice dishes just as regular soy sauce is. When added to these dishes, it will give them a sweet, salty, pungent flavor.