Natto is fermented, but not sour, that chopsticks stirred when it will pull the silk, show you a paragraph of home natto practice

general family でも纳豆を作ることができる。 Necessary なものは、十分に蒸したか茹でたかした大豆と纳豆菌(纳豆そのもので代用可)と、纳豆菌が生育する适度な温度(30～45°)、适度なhumidity、适度な时间(1～2日)、十分なacidすである。 Moderate temperature, moderate time and acidity are not enough for natto to be cooked. Moderate humidity and drying of soybeans. Fumigation time is too long, and it is also the same as rotting the anemone odor, so it is not a good idea.

A rough translation of this is: it is important that soybeans are completely steamed or boiled and natto bacteria and a temperature of about 40 degrees, the right humidity, the right amount of time for 1 to 2 days, it will produce acidity, without the right temperature and time, there is no acidity, soybeans are boiled soybeans, without the right temperature it will become dry soybeans, and if the time is too long then it will be ammonia and become stinky

You Look again to see which part of yours is out of place