Under normal circumstances, Astragalus membranaceus is slightly sweet in water and will not turn sour. If it turns sour, it's because you've been soaking it for too long. In summer, Astragalus membranaceus should be soaked in water for a normal day and then poured out. It is best not to spend the night, because Astragalus membranaceus contains a lot of polysaccharides, which is easy to deteriorate after a long time. In addition, it is best to put Astragalus membranaceus in a health pot when soaking in water, which can eliminate many bacteria and help to dissolve the effective components of Astragalus membranaceus.