In the Northern Hemisphere, starch is a component of almost every meal. Starch is a polysaccharide, literally meaning many sugars, consisting of glucose units bonded together to generate long-chain molecules. Humans, animals and plants use polysaccharides to provide energy, store fuel and supply structural support. There are two different kinds of starch molecules, amylose and amylopectin, that are present in varying quantities to produce a myriad of food starches. Most starches contain both amylose and amylopectin molecules.
Amylose
Amylose composes 20 to 30 percent of most plant starches. The structure of the amylose molecule is linear with a chain-like formation.This formation contributes to the indigestibility and gel-like consistency of this starch molecule. Few foods are truly high in amylose starch, as most starches contain primarily amylopectin. Some bioengineered starches contain 100 percent amylose, like high-amylose cornstarch. Specialty foods made with commercially-produced cornstarch, like high-amylose crackers, contain approximately 70 percent amylose.
Legumes, such as lentils, soybeans, butter beans and black beans, contain 30 to 40 percent amylose. Foods high in amylose are not easily digested and reach the large intestine without being metabolized. Thus, high-amylose foods may serve as a prebiotic, an agent promoting the growth of healthy bacteria in the intestines. Additionally, foods with high-amylose content may lower your body's insulin and glucose response, potentially decreasing your cholesterol and triglyceride levels and risk for diabetes.
Amylopectin
Amylopectin comprises 70 to 80 percent of the majority of plant starches. However, some starches, like waxy cornstarch, waxy sorghum starch and waxy rice starch, contain 100 percent amylopectin. The molecules of amylopectin are broad and branched, which contributes to its water solubility and paste-like consistency. These properties make amylopectin useful for commercial production of pastes, lubricants and adhesives. These characteristics are also useful in cooking, as high-amylopectin rice is preferred in Asian cooking because of the sticky texture. Additionally, the adhesiveness in amylopectin holds breads and pastries together and provides the thick consistency in gravies and puddings.
Types of Food Starches
Types of food starches include cornstarch, potato starch, wheat starch, tapioca starch, rice starch, sago starch and sorghum starch. Cornstarch comprises the majority of the demand for starch worldwide. Some forms of commercially produced cornstarch are high in amylose, while natural cornstarch is high in amylopectin. Wheat, potato and tapioca starches are secondary sources of starch in meeting consumer demands.
Foods with Starch
Starch is added to some foods to provide viscosity, lengthen shelf life, increase adhesiveness, enhance clarity or retain oil. Foods with added starch include puddings, gravies, sauces and pie fillings. Other foods with added starch are cereals, biscuits, bread, cake, pastry, muffins and popovers. Additionally, dry beverage mixes, canned soups, nondairy creamers, chips, pretzels, icing, licorice, low-fat dressings and pet food contain starches.
References
- Elmhurst College: Starch
- Oregon State University: Starch
- International Starch Trading: Industrial Food Starches
- GMO Compass: Amylose, Amylopectin (Starch)
- Handbook of Prebiotics and Probiotics Ingredients: Health Benefits and Food Applications; Natural Resistant Starches as Prebiotics and Synbiotics; Susan Cho, et al.
- The American Jounral of Clinical Nutrition; Diets Containing High Amylose Vs Amylopectin Starch: Effects on Metabolic Variables in Human Subjects; K. M. Behall, et al.
- Oregon State University: Cooking up Change in Thailand
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