Soy Sauce - Production - Traditional

Traditional

Traditional soy sauces are made by mixing soybeans and grain with mold cultures such as Aspergillus oryzae and other related microorganisms and yeasts (the resulting mixture is called "koji" in Japan; the term "koji" is used both for the mixture of soybeans, wheat, and mold; as well as for only the mold). Historically, the mixture was then fermented naturally in giant urns and under the sun, which was believed to contribute additional flavors. Today, the mixture is generally placed in a temperature and humidity controlled incubation chamber.

The production process of traditional soy sauces consists of several steps taking months to complete:

1. Soaking and cooking: The soybeans are soaked in water and boiled until cooked through. The wheat is roasted and crushed.
2. Koji culturing: An equal amount of boiled soybeans and roasted wheat are mixed to form a grain mixture. A culture of Aspergillus spore is added to the grain mixture and mixed or the mixture is allowed to gather spores from the environment itself. The cultures include:
   • Aspergillus: a genus of fungus that is used for fermenting various ingredients (the cultures are called koji in Japanese). Three species are used for brewing soy sauce:
     • A. oryzae: Strains with high proteolytic capacity are used for brewing soy sauce.
     • A. sojae: This fungus also has a high proteolytic capacity.
     • A. tamari: This fungus is used for brewing tamari.
   • Saccharomyces cerevisiae: the yeasts in the culture convert some of the sugars to ethanol which can undergo secondary reactions to produce other flavour compounds
   • Other microbes contained in the culture:
     • Bacillus spp.(genus): This organism is likely to grow soy sauce ingredients, bring to generate odors and ammonia.
     • Lactobacillus species: This organism produces a lactic acid increases the acidity in the feed.
3. Brewing: The cultured grain mixture is mixed into a specific amount of salt brine for wet fermentation or with coarse salt for dry fermentation and left to brew. Over time, the Aspergillus mold on the soy and wheat break down the grain proteins into free amino acid and protein fragments and starches into simple sugars. This amino-glycosidic reaction gives soy sauce its dark brown colour. Lactic acid bacteria ferments the sugars into lactic acid and yeasts produces ethanol, which through aging and secondary fermentation produces numerous flavour compounds typical of soy sauce.
4. Pressing: The fully fermented grain slurry is placed into cloth-lined containers and pressed to separate the solids from the liquid soy sauce. The isolated solids are used as fertilizer or fed to animals while the liquid soy sauce is processed further.
5. Pasteurization: The raw soy sauce is heated to eliminate any active yeasts and molds remaining in the soy sauce and can be filtered to remove any fine particulates
6. Storage: The soy sauce can be aged or directly bottled and sold.