Hydrolyzed Protein and its Role in Soy Sauce

Soybeans, wheat, salt, water.

After these basic soy sauce ingredients, the ingredient that makes its presence felt the most is probably hydrolyzed protein, also known as amino acid liquid. It is also a keyword that often comes up when discussing soy sauces distributed around the world. Some soy sauces contain it while others do not.

Soy sauce containing hydrolyzed protein is also produced outside of Japan and is distributed worldwide. When looking at product shelves around the world, soy sauce is often lined up based on whether hydrolyzed protein has been added or not. As for Japan, the home of soy-sauce making, the “manufacturing method” label on the product will change depending on if and when the hydrolyzed protein is added.

Soy sauce without hydrolyzed protein is “hon-jozo.” The natural process, which utilizes enzymes and bacteria, incurs higher raw material costs and takes longer time. “kongo-jozo” is soy sauce fermented and aged by adding amino acid liquid to the “moromi” of hon-jozo before the soy sauce is pressed. Fermentation and maturation for at least one month can soften the unique aroma of amino acids. “kongo” is a soy sauce made by adding amino acid liquid to hon-jozo soy sauce. JAS Law requires that the amount used should be 80% or less based on the nitrogen equivalent. In some cases, “enzyme decomposer” is added instead but the name of the manufacturing method remains the same.

Amino acid liquid contains umami components that are made by breaking down vegetable proteins such as soybeans, corn, and wheat with hydrochloric acid. By decomposing it with hydrochloric acid, it can be efficiently converted into umami liquid in a short period of time. Outside of the soy sauce industry, it is also referred to in other ways, such as “hydrolyzed protein.” In addition to soy sauce, amino acid liquid is used in various processed foods around the world, such as pickles, tsuyu, tare, ramen soup, tsukudani, kamaboko, hamburgers, curry, instant noodles, etc, and foods can have “umami” or made richer in taste by adding it. “Enzyme-degraded seasoning liquid” used in place of amino liquid is made by using proteolytic enzymes to break down vegetable proteins such as soybeans, corn, and wheat, while “fermented element-degraded seasoning liquid” is made by fermenting and breaking down wheat gluten. Both amino acid liquid and enzyme-degraded seasoning liquid are liquids containing umami components.

The soy sauce industry has long searched for ways to shorten the fermentation and aging period of moromi, and to increase the utilization of this valuable ingredient. The main reason for this is that it takes nearly a year from the time the raw materials are prepared to the time when they become finished products. This length is extremely long compared to many types of sake and miso. Another reason is that the utilization rate of useful components in raw materials is lower in comparison to other food industries. After a series of frantic development efforts aimed at “making soy sauce in a shorter period of time” and “increasing the utilization of valuable materials,” “amino acid liquid” was finally born, with a short production time and a high material utilization rate.

Amino acid liquid was especially useful at the time of food shortage caused by the Second World War. After the outbreak of the Second Sino-Japanese War in July 1937, profits for soy sauce producers gradually declined due to soaring prices and shortages of raw materials and containers. Although appeals were made to the government through the National Soy Sauce Association, the government requested “lower quality,” “cheaper containers,” and “lower commissions for intermediary traders,” and assuring quantity was made the priority rather than dealing with quality issues. During the challenging war period when it was difficult to secure soybean raw materials, low quality alternatives such as so-called “substitute soy sauce” was made from the decomposed liquid juice of seafood and seaweed. Being able to add amino acid liquid was actually a saving grace.

As raw materials became available again and production techniques improved, it became unnecessary to add amino acid liquid to soy sauce, and many regions returned to the hon-jozo method. On the other hand, there are also many other regions that continue to add amino liquid to brewed soy sauce to produce umami-rich soy sauce which are identified as the “local flavor.”