The purpose of soaking is to soften corn kernels, decompose external protein, and easily separate germ, fiber, protein and starch. In order to shorten the soaking time, prevent microbial fermentation in the soaking process, and make protein and starch easy to separate, in addition to adding water, microbial inhibitors should be added by heating (the temperature is generally controlled at about 50℃, and sulfur crop microbial inhibitors will produce SO2) to produce lactic acid during the soaking process, so as to keep the pH value of the solution below 4. Therefore, soaking water is the existing state of acidic colloidal solution. Wherein the solids are substantially soluble solids.