Why are soaked dried soy beans cooked before fermenting?

Question

Is it necessary to cook soaked dried soy beans before fermenting them?

Answer 1

No. Both tofu and miso require cooking the soybeans to work.

For miso, the soybeans must be mashed into a paste, which doesn't really work with raw soybeans. Further, the koji culture grows on the starches and sugars present in cooked soybeans, not raw ones. So creating a miso from raw soybeans would require you to obtain a different fungal culture designed for them, and the result probably wouldn't be miso.

Tofu is made through soymilk, which must then be boiled to make it coagulate. So while the soymilk itself is made with raw soybeans, if you don't boil it, you don't get tofu, just thickened soymilk.

Also note that raw soybeans are poisonous, so in addition to producing a product, you'd have to be sure that any fermentation process you cultivated would successfully breakdown all lectins and protease inhibitors in the beans. While fermentation is known to break down the saponins, the other two unhealthful chemicals usually require heat.

Answer 2

From https://www.culturesforhealth.com/:

...beans must be cooked before they can be eaten. They are very tough, and need rehydrating, and the cooking process further breaks down those hard-to-digest starches and anti-nutrients.

So even if those beans ferment while soaking, you will still have to cook them in order to make them edible. That cooking process will eliminate any beneficial enzymes or probiotics that have been added to the beans through the fermentation process.