From the color point of view, flour and flour products without whitening agent are milky white or yellowish. For example, flour with whitening agent is white or pale, followed by flour with better quality, which smells slightly sweet and fragrant. Anyone who smells abnormal smells such as mildew and sour taste is of poor quality. You can also twist the flour by hand. If it feels soft, it means the quality is good. If it feels too smooth, it means the quality is poor. Sometimes it may be mixed with talcum powder and flour mixed with talcum powder. When kneading dough, the dough is loose and soft, and it is not easy to form.