What is the brewing method of Shanxi mature vinegar?

Shanxi mature vinegar is a traditional vinegar in China, which is famous for its unique flavor. Its characteristics are sweet but not strong, sour but not bitter, fresh but not salty, spicy but not strong. Vinegar koji takes barley, peas and black beans as raw materials, and wheat husk, chaff, wheat straw and sorghum straw as koji beds, which are moldy at 25 degrees. When making vinegar, sticky yellow rice and sorghum are cooked together into porridge, and after more than one month, 20% of the vinegar koji is added to make vinegar mash. Then add bran and small rice bran, mix them evenly, ferment at 35℃ in the koji room, and after 10 days, make vinegar residue, then move it into a pouring pot to pour vinegar. After sun exposure, condensation, ice fishing and other processes, the new vinegar is continuously fermented and concentrated, and its flavor is getting better and better. It will be eaten in a year or two, so it is called "old vinegar". This is its traditional production method. This formula and technology have been basically formed in Qi Yaomin's Book, so its history can be counted as 1400 years.