Starches in FoodOpen image in new window
Starch is a plant polysaccharide stored in roots and seeds of plants, and in the endosperm of a grain kernel. It provides humans with energy (4 cal/g), and is hydrolyzed into glucose, supplying the glucose that is necessary for brain and central nervous s
- PDF / 401,736 Bytes
- 13 Pages / 504.567 x 720 pts Page_size
- 75 Downloads / 172 Views
Starches in Food
Introduction Starch is a plant polysaccharide stored in roots and seeds of plants, and in the endosperm of a grain kernel. It provides humans with energy (4 cal/g), and is hydrolyzed into glucose, supplying the glucose that is necessary for brain and central nervous system functioning. Starch grains, or granules, contain long-chain glucose polymers and are insoluble in water. Unlike the small molecules of salt and sugar, the larger starch polymers do not form a true solution. Instead, starch granules form a temporary suspension when stirred in water. As uncooked granules, each may swell slightly when it absorbs water. However, once starch is cooked, the swelling is irreversible and the starch leaches out. This characteristic of starch granules enables starch to be used as a thickener. Overall, the characteristics of a finished starch food product are determined by several factors: the source of starch, concentration of starch used in a formulation, the temperature and time of heating, and other components used with the starch, such as acid and sugar. There are many types of starch and modified starches. These thicken, prevent curdling, and stabilize cooked salad dressings, dips, gravies, desserts, and more. Intermediate, shorter chain products from starch breakdown, known as dextrins, may be used to simulate fat in salad dressings and frozen
desserts. For example, wheat, potato, and tapioca maltodextrins may be used as fat replacers. These provide the viscosity and mouthfeel of fat in a food product, yet, with reduced calories compared to fat.
Starch Sources in the Diet Starch sources are numerous, with common ones derived from cereal grains such as wheat, corn, or rice. Wheat yields a cloudy, thick mixture, while cornstarch produces more clear mixtures such as gravies or sauces. Vegetables, roots and tubers, including the root of cassava, and potatoes, are frequently used in the preparation of gluten-free foods, where persons with wheat allergies or intolerances do not use any wheat as a thickener. Specialty starches are available commercially and some may be available to the consumer, perhaps purchased through specialty food stores. Another source of starch is legumes such as soybeans or garbanzo beans. As well, sago is a powdery starch obtained from the stems and trunks of the sago palm in tropical Asia. Sago may be used as a food thickener as well as a fabric stiffener. Fruits such as bananas may also be sources of starch. Thus it may be seen that starch may come from a variety of sources. Depending on the source, starches may also have different crystalline structures.
V.A. Vaclavik and E.W. Christian, Essentials of Food Science, 4th Edition, Food Science Text Series, DOI 10.1007/978-1-4614-9138-5_4, # Springer Science+Business Media New York 2014
39
40
4
Starches in Food
Starch Structure and Composition The starch granules from various grains differ in size, ranging in size from 2 to 150 μm. The shape of starches may also vary—being round or polygonal, as seen in the photomicrograph
Data Loading...
