8-Hydroxygenistein (8-OHG) is an antioxidant that effectively scavenges NO and O2-. It is a type of ortho-dihydroxyisoflavone (ODI) and is abundantly found in thick and fermented soy sauces, exhibiting stronger antioxidant properties than its parent compound, Genistein. The concentration of 8-Hydroxygenistein is positively correlated with the antioxidant capacity of soy sauce (r=0.959) and maintains high stability even after being heated in boiling water for 60 minutes. It is effective in preventing oxidative damage during the brewing and storage of soy sauce, offering potential applications in food antioxidant research.