Kikkoman soy sauce does not easily spoil or become unsafe to consume over time because its high sodium content and natural fermentation properties act as powerful preservatives against microbial growth. However, manufacturers print "best by" dates on bottles to guarantee optimal flavor freshness. While an unopened or properly stored bottle will remain safe past that date, opened bottles exposed to oxygen for years will gradually lose their vibrant aromatic compounds, rich color, and balanced umami flavor profile.