Yes According to Sohu News Network, the saccharifying enzyme in Shantou old preserved vegetables has completely decomposed nitrite, and nitrite itself is not a carcinogen. Dried vegetables will turn dark black after being stored for more than ten years or even decades, which is more precious for decades-old preserved vegetables and has the effect of nourishing and preserving health. So Shantou's 25-year-old preserved vegetables can be eaten when they turn black.