The color of the stinky dried seeds is not dyed by chemical pigments

Basically not. It is estimated that no one has seriously studied why stinky tofu turns black, but the principle can refer to tempeh, soy sauce, and - water. Under the fermentation action of various fungal bacteria (Aspergillus oryzae, lactic acid bacteria, yeast, etc.), soy protein is broken down into fragments or individual amino acids, carbohydrates are broken down into oligosaccharides or monosaccharides, and even further into lactic acid and alcohol.

All of these products will undergo secondary fermentation, and the final thing will make up the unique taste and smell of each fermented food (different production methods, different flora, and different tastes). In this process, these raw materials undergo a chemical reaction called the Maillard reaction, which causes glucose and other sugars to combine with amino acids to form a class of substances called melanoids. That's why most of these things are brown or black.

To sum up, as long as the stinky tofu is only made by normal and regular methods, it is not dyed with chemical pigments (it should be called chemical pigments, because essentially all pigments are chemicals). However, isn't there a race of profiteers in this world, and technology can't make up medicine. If you eat stinky tofu that looks black but doesn't taste strong at all, you can really wonder if the color is blended.

Of course. The "secret recipe" for the production of "Hubei Stinky Dried Seeds": first cut the old tofu into the size of a matchbox, put it in the pot and boil, after the pot boils, put a packet of ferrous sulfate into the pot, cook for a few minutes, and the tofu is dyed purple and black and fished out.

After the black tofu is cooled, it is soaked in a black bucket filled with "stinky water". "Stinky water" is a "stinky brine" boiled from rancid tofu, shiitake mushrooms, tea, snails, etc., and the chemical raw material ferrous sulfate reacts with the fermented product to produce iron sulfide, which is inky black and smells. After a few hours of fermentation, it becomes the famous "Hubei stinky dried seeds".

Many vendors also add ammonia bicarbonate to the "stinky brine", which not only tastes more smelly, but also makes the thin-looking tofu slices "hairy" when fried.

During the fermentation process, dried tofu is easily contaminated by microorganisms, and at the same time, it will volatilize a large amount of salt and basic nitrogen, which is not easy to eat! It smells bad and tastes good, which is the characteristic of stinky dried seeds.

The raw materials of black and white stinky dried seeds are soybeans.

The black, stinky dried seeds are not blackened by mold.

It is the addition of dye.

If it's an edible coloring, it's delicious.

Otherwise, it's toxic.

There have been reports of unscrupulous businessmen dyeing black and smelly dried seeds with industrial dyes.