This technology involves mixing soy sauce and rice bran in a 7:3 to 6:4 (v/w) ratio, adding 1–4 mg of PLP (pyridoxal-5'-phosphate) per 100g of the mixture, and creating anaerobic conditions to rapidly increase the gamma-aminobutyric acid (GABA) content in the soy sauce.
GABA is a functional ingredient known for its calming, stress-relieving, and blood pressure-lowering effects. However, natural plant sources often lack sufficient levels to provide physiological benefits, leading to the development of GABA-enriched products like green tea, rice germ, and germinated brown rice. Methods for increasing GABA in soy sauce have rarely been reported, and there has been a need for new materials and processes beyond existing functional soy sauce technologies that rely on medicinal herbs or mushroom mycelia.
This technology utilizes the glutamate decarboxylase in rice bran to convert the abundant glutamic acid in soy sauce into GABA, while supplementing with PLP—a coenzyme for the enzyme—to accelerate the reaction. Anaerobic treatment is performed at 30–50℃ for 2–24 hours. By pre-spraying rice bran with water, soy sauce, protein hydrolysates, or pH-adjusted ionized water to reach 20–60% moisture, and then adding PLP under anaerobic storage, one can prepare rice bran with pre-enriched GABA. This method is applicable to acid-hydrolyzed, brewed, and enzymatically hydrolyzed soy sauces. It can be used to produce premium functional soy sauce, low-sodium seasonings for blood pressure management, and GABA-fortified sauces and dressings, allowing for the upcycling of rice bran—a milling byproduct—to impart GABA functionality to soy sauce in about a day without long-term fermentation.
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