Due to the influence of climate and rainfall, temperature changes and seasonal changes in the milk source, the solubility of raw materials is somewhat different, so a small amount of insoluble particles may be found to stick to the wall or precipitate during brewing. These insoluble particles are normal milk powder particles, which do not affect the normal nutritional components and consumption. As long as you buy it through regular channels, there is generally no problem. You can raise the water temperature of the prepared milk powder, and it will generally dissolve a little when you pour a spoonful.