What does it mean for a knowledgeable friend to talk about pure grain solid state brewing?

solid state brewing is a brewing process of liquor, and pure grain refers to the use of grain crops as brewing materials. That is to say, pure grain liquor is the solid-state brewing process of pure grain. Generally, only high-quality liquor will be brewed by solid-state method, because the brewing cycle is relatively long. For example, Jianzhuang wine, with only five kinds of grain as raw materials and no other industrial raw materials, is naturally delicious.