Types and differences of starch

Chemically, starch is a homogeneous polysaccharide formed by the condensation of hundreds (amylose) or thousands (amylopectin) of glucose molecules. Its molecular shapes are linear (soluble in hot water) and branched (insoluble in hot water), glutinous rice starch is all branched, some bean starches are all linear, while general starch has both. Starch is widely found in grains (rice, wheat and corn), fruits (chestnuts and ginkgo), tubers (sweet potatoes), tubers (potatoes) and corms (water chestnuts and taro) of plants, and it is the main energy storage form of plants. Starch is insoluble in water, but it will absorb water and swell in hot water to become a viscous translucent colloidal solution.

(1) Wheat products

The flour we eat every day comes from the seeds of the gramineous plant wheat, which is the most widely planted grain in the world. Different from other grains that are eaten directly after shelling, wheat has tough surface bran and fragile internal endosperm, so it is difficult to be processed into whole grains, so it can only be ground into flour. The biggest difference between wheat flour and other grains is that two kinds of protein unique to wheat can combine to form gluten with good elasticity and ductility (that is, it can be stretched for a long time without breaking), so only wheat can make pasta products with various patterns and different tastes. The content and quality of gluten in flour (that is, the content of two kinds of protein) depends on the variety and planting process of wheat crops, not the flour processing process, but the content of protein may change during processing and storage.

gluten: it is the protein part extracted from flour, which can be mixed with cold noodles, oil gluten and other China specialties.

Wheat starch: also called Chengfen, Chengmian, Tingfen and Tingmian, is the starch (gluten-free) left after protein is removed from flour. It is very white in color and is the main raw material of crystal cakes and cold noodles.

High-gluten flour: also known as bread flour, protein content is above 11.5%, which has the strongest gluten. It is used to make bread, pizza, puffs, fried dough sticks, thousand-layer cakes and other snacks that need to rely on strong elasticity and ductility to wrap bubbles and oil layers in order to form a loose structure.

medium gluten flour: the most common flour, plain flour, with protein content of 9.5-11.5%, is used to make most Chinese snacks such as steamed bread, steamed stuffed bun, jiaozi, pancakes, noodles and twist.

low-gluten flour: also known as cake flour, protein content is 6.5-9.5%. It can be made by mixing four parts of medium-gluten flour with one part of corn starch (other starches are also acceptable). It is suitable for making cakes, biscuits, egg tarts and other loose, crisp and inflexible snacks.

self-raising flour: self-raising flour sold in supermarkets is flour mixed with a certain proportion of yeast, baking powder and other chemical additives, which only needs water when used, and can save fermentation time. Self-raising flour should be used according to the instructions on the package, because different product formulations may have different methods of use.

whole wheat flour: wheat seeds are composed of bran, endosperm and germ. The bran is hard and difficult to digest, and the germ is rich in oil and easy to rancid, so the flour is made of endosperm. However, bran provides rich dietary fiber, which is very beneficial to human digestion. Therefore, whole wheat flour is a common flour made of endosperm with ground bran. For bread, cake, noodles and other different purposes, the proportion of bran added, the size and shape of bran are also different, so in fact, whole wheat flour is not a coarse product directly ground by whole wheat grains, but a more complicated refined product.

In the West Point recipe, what kind of flour is needed will be specially indicated. Generally, medium-gluten flour can be used instead of high-gluten flour or low-gluten flour without obvious difference. At present, the flour sold in the grain area of domestic supermarkets is mainly medium-gluten flour suitable for Chinese pasta, while the "refined flour", "special flour" and "rich flour" are marked to indicate the processing fineness of flour, not the gluten content of flour. "jiaozi flour" is medium gluten flour and "bread flour" is high gluten flour. In the imported food area of large supermarkets, you can also buy completely imported flour with detailed classification and specific use, as well as all kinds of ready-mixed flour containing other powder raw materials that can be used directly, but the price is also very expensive.