Starches from grains tend to share several characteristics. Their starch granules are medium-sized, and contain small but significant amounts of lipids (fats, fatty acids, phospholipids) and protein. These impurities somehow give the starch granules some structural stability, which means that it takes a higher temperature to gelate them; and they lend a cloudiness and distinct “cereal” flavor to starch-water mixtures. Light that passes right through a gelated mesh of pure starch and water is scattered by tiny starch-lipid or starch-protein complexes, producing a milky, impenetrable appearance. Grain starches contain a high proportion of moderately long amylose molecules that readily form a network with each other, and so make sauces that quickly thicken and congeal when cooled.