Starch

Starch is a substance found in plants that is made up of long chains of glucose, a simple sugar. The molecules can be simple and linear or complex, with glucose branching off the chain. The glucose is produced during the process of photosynthesis, and what is not needed is stored by the plant for later use. Some plants, like potatoes, store the starch in fleshy tubers, which humans and animals eat. When humans and animals eat foods that contain starch, their digestive systems break down the starch into glucose and use the energy.

Ancient societies—including the Chinese, the Egyptians, and the Greeks—used starch for a variety of purposes, including papermaking. Since the sixteenth century, starch has also been used to stiffen clothes. It is commonly used in many commercial industries, including baking and confectionery making, pharmaceuticals and cosmetics, paper and board production, and as feed for pets, livestock, and aquatic creatures. Much of the starch used in modern applications is made from potatoes, maize, wheat, and tapioca.

Background

Humans have been consuming starch since prehistory. The foods that contain the most starch provide a great deal of energy, so such crops have been vital to human survival.

Experts do not know when humankind began using starch for more than food. Early recorded evidence dates back to 4000 BCE, when Egyptian records describe using a starchy adhesive to glue together papyrus, a precursor to paper made from the stems of water plants. The Romans were separating starch from grain by 170 BCE. The Chinese were using starch to make paper that would absorb less ink in 312 CE. Many textile industries in Western Europe were using starch as a stiffener by the sixteenth century.

In 1804, French chemist Edme-Jean Baptiste Bouillon-Lagrange discovered that starch changed to a new substance that dissolved easily in water after roasting. This new substance, dextrin, can also be formed through other methods of hydrolysis, including through the use of acid or through fermentation, to divide the long molecular chains. Dextrin, which is a gummy substance, is a glucose polymer that has become a common food additive and a source of fiber. Dextrins are often used as thickening agents in sweets and dairy products.

Soon after Bouillon-Lagrange's discovery, Russian chemist Gottlieb Kirchhoff heated starch with sulfuric acid, turning it into a sugar—corn syrup. It was later named glucose, a type of sugar that is commonly found in honey and fruits, including grapes. Kirchhoff was trying to find a replacement for cane sugar, which was not accessible during the Napoleonic Wars. His work was not a success despite his discovery, because glucose is less sweet than cane and beet sugar, and the yield was small. His work did lead to the discovery of other modified starches and starch sweeteners, however.

The drawbacks of working with acids to modify starches were overcome by replacing them with enzymes late in the twentieth century. Enzymes are also used to process raw sugar, which contains some starch found naturally in cane and sugar beets, into refined sugar.

Most of the starch produced in Europe was made from wheat until the eighteenth century. Since then, potatoes have been the primary source of starch, though maize and wheat are also important sources. The European Union is a major source of starch. Thailand, which produces tapioca starch, is one of the world's largest exporters of the product.

Overview

Potatoes, wheat, maize, and tapioca (cassava) are among the most common sources of starch. Some cultures have a tradition of using starches from foods that are readily available. For example, cassava root is a staple in many regions of Africa, so cassava (yuca) starch is commonly used.

About 75 percent of the starch produced by commercial operations is used for non-food applications. Starch products are vital in leather tanning, the manufacture of plastics, and the production of adhesives and coatings. Starch is used in producing biodegradable plastics, polyurethanes, and resins and in the construction industry in concrete mixtures, insulation, and plasters. It is also used in metal and mineral processing and oil drilling.

Starch is used in many cosmetics and health products as well. These products include makeup, toothpastes, creams, lotions, and liquid medicines. It is used to manufacture antibiotics, penicillin, blood plasma substitutes, and other health care and medical products.

While starch has been used to stiffen fabric for centuries, it also has a history in textile dyeing. Several cultures, including groups in Japan and Africa, have used starch paste in resist dyeing, or batik dyeing. Rice starch has commonly been used in Japanese textile dyeing, while both rice starch and cassava starch pastes have been used in Africa. The starch is applied to the cloth and resists the dye, allowing the artist to make various designs.

Starch is also used in the production of fabric. It is added to strands to strengthen the fibers and to make it moisture resistant. In addition, the substance is often used in the textile printing process to stabilize inks. Starch is used to manufacture detergents that are biodegradable, nontoxic, and suitable for sensitive skin as well.

In the food industry, starch is used as a thickening agent in custards, sauces, and soups; as a stabilizer for certain foods; and as a binder to retain moisture in such foods as processed meats. Starch is included in baked goods, such as biscuits, to maximize crispness and increase volume. Dextrose and glucose syrups are commonly used to sweeten candies and in the manufacturing of jellybeans, hard candies, toffee, and many other sweets. It is also common to dust candies with starch to keep them from sticking together. Glucose syrup is often used in fruit products such as canned fruits, jams, and preserves. It is also used in the production of beverages and in fermentation, not only to produce alcohol but also to make yeast and other products. Cassava starch and molasses are the main ingredients of monosodium glutamate (MSG), which is often manufactured in Latin America and Asia. MSG is a common flavor enhancer in many foods.

Bibliography

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