Durum wheat is the main constituent of most pasta, and is a hard, high-protein wheat. It provides most flour used for pasta-making and is generally milled into very fine semolina. It is a nutritious winter wheat resistant to spoilage during transport and storage. It has a golden berry, vitreous in consistency. When it is milled, it shatters into grains known as semola or, depending on the grade, semolina. If it is used for bread it should be mixed with other grains and needs to be kneaded a great deal.