What is Starch?
Starch is a carbohydrate found in many plants and is a large part of the human diet. Common sources of starch include corn, wheat, potatoes or tapioca. It is a polysaccharide, with an abundance of glucose molecules. Whether in its original form, or as one of its derivatives, starch has a variety of uses in the food industry, as well in manufacturing.
Food starches are added to thicken or stabilize products such as puddings, soups, sauces, pie fillings, salad dressings and many others. Modified versions of starch are also frequently used in foods that have a low pH or can not be heated.1
Starch comes from the middle english word “strechen,” meaning “to stiffen.” Yet use of the carbohydrate can be traced back much further. There are some references of ancient Egyptians sticking papyrus together with a starch glue and Romans extracting starch from grain in 170 BC. The first recorded starch discovery was by French chemist Bouillon Lagrange in 1804. A few years later, Russian chemist Gottlieb Kirchhoff found potato starch could produce sugar by an acid hydrolysis.
Through the 18th century, wheat was the primary source of starch. However, potatoes and maize soon grew in popularity as well. During the 1940s, an increase in dry and processed foods grew the modified starch industry. The FDA is in charge of regulating the amount and types of modification.1
In commercial production, maize, potato, tapioca, wheat, rice and arrowroot are sources for starch. The extraction depends on the original plant or root being used. In the U.S., cereal grains are the most common source.2 ‘
Kernels are cleaned and soaked in water, to enlarge and soften them. They are then milled to crack the outer shells and then a separator frees the germ. The germ includes starch, fiber and gluten. First, a fine grinding and screening process separates the fiber. The starch and gluten go through a centrifuge which spins out the less dense gluten. From there, the starch ether is dried and sold as powder, or in the case of corn, converted into syrups, sweeteners, dextrose or fructose.3
When used in food, starch assists with texture, viscosity, gel formation, adhesion, binding, moisture retention and can be used as a fat substitute. It also works as a emulsifier, stabilizer, and a clouding or glazing agent.4 However, it’s main use in the food industry is a thickening agent.
There are two types of starches used:
- Native Starch, or the original form of starch powder extracted from plants. Starch in its pure form is a white, tasteless, odorless powder that is insoluble in cold water or alcohol. It’s used to thicken and stabilize many custards, desserts, sauces, and instant foods
- Modified Starch, is native starch that have been modified physically, enzymatically, or chemically. This is done to enhance or diminish specific attributes of starch, specializing the modified starch for thickening, gelling, encapsulating or such.
Starch thickens food through gelatinization and retrogradation. Heat causes starch to absorb water and swell, while increasing viscosity and clarity. Once the maximum viscosity is reached, the cells move apart and decrease viscosity. When the product begins to cool again, viscosity increases, making the solution cloudy and eventually forming a gel. The strength of the gel depends on the type of starch and how much is used.
Starch is composed of two glucose polymers – amylose and amylopectin. Although it ranges from source to source, starches usually have 20 to 25 percent amylose and 75 to 80 percent amylopectin. However, grain starches tend to have a higher amylose content compared to ones from other plants.5
The FDA considers starch safe for food use. Starch made from corn can be labeled as corn starch or simply starch. However, other starches must include the original source, such as “potato starch.”
The FDA allows starch to be modified with hydrochloric acid or sulfuric acid. It may also be bleached, esterified, etherified or treated with chlorine. The FDA regulates any modified starch under the Food Additives Amendment. Click here for a full list of requirements and specifications
1. BeMiller, James N., and Roy Lester. Whistler. Starch: Chemistry and Technology. London: Academic, 2009.
2. Nuss, Emily T., and Sherry A. Tanumihardjo. “Maize: A Paramount Staple Crop in the Context of Global Nutrition.” Comprehensive Reviews in Food Science and Food Safety 9.4 (2010): 417-36.
3. Rittenauer, M., L. Kolesnik, M. Gastl, and T. Becker. “From Native Malt to Pure Starch – Development and Characterization of a Purification Procedure for Modified Starch.” Food Hydrocolloids 56 (2016): 50-57.
4. Patel, B.k., R.d. Waniska, and K. Seetharaman. “Impact of Different Baking Processes on Bread Firmness and Starch Properties in Breadcrumb.”Journal of Cereal Science 42.2 (2005): 173-84.
5. Kim, Sanghoon, Atanu Biswas, Mukti Singh, Steven C. Peterson, and Sean Liu. “Thermal Dissolution of Maize Starches in Aqueous Medium.”Journal of Cereal Science 56.3 (2012): 720-25.