|1. Many plants store large quantities of starch in underground structures that are modified stems or roots. Botanically, these structures have several functions: as food reserves, for asexual reproduction, and as the starting point for renewed growth after dormancy. Some of these storage organs are starchy staples that include some of the world’s foremost crops. In addition to their direct consumption, potatoes and cassava are also sources of commercial starch, which has many applications in both food and nonfood industries.
2. Native to the highlands of South America, the potato was the dietary staple of the ancient Incan civilization and was introduced to Europe in the sixteenth century. Cultivation of these tubers spread slowly throughout Europe, becoming the food of peasants. The crop was so successful in Ireland that it led to a population explosion and, later, massive famines when late blight of potato destroyed the crops in the 1840s. Today, about one-half of the U.S. potato crop is processed to make French fries, potato chips, and dehydrated flakes. This use of potatoes continues a long tradition; Peruvian Indians have prepared a processed potato product, chuño, for over 2,000 years. The potato plant is a member of the nightshade family, the Solanaceae. Many members of this family are poisonous; in fact, the potato contains toxins in all parts except the tuber. Potatoes are cultivated by seed potatoes, which are small tubers or cut tuber pieces containing at least one “eye.” Although this method of asexual reproduction is fast and produces plants with desired characteristics, all the offspring are genetically identical and share susceptibility to adverse environmental conditions and diseases.
3. Sweet potatoes are storage roots of a plant in the morning glory family and are unrelated to the white potato. The sweet potato is believed to be native to tropical South America; archeological evidence dates its cultivation back several thousand years in Peru. It was also cultivated in several Pacific islands and New Zealand. Evidence of its early cultivation in Polynesia suggests an earlier introduction by seafaring natives or by the natural dispersal of seeds by birds or ocean currents. Although of relatively minor importance in the United States, the sweet potato today is a significant crop throughout the tropics and some warm temperate regions.
4. Cassava is a tuberous root that is another important starchy staple vital to the food supply of millions in the tropics. Cassava ranks fourth behind rice, sugar, and corn as a source of calories for the human diet in tropical countries. Although native to South America, cassava is now cultivated throughout the tropics. Cassava varieties are classified as either sweet or bitter based on the concentration of hydrocyanic acid. Various methods of processing have been developed to detoxify cassava and make it safe to eat.
5. Other underground crops include yams and taro, which are important staples in tropical areas, especially the South Pacific islands. Jerusalem artichoke was a Native American staple that currently is of interest to nutritionists because it is rich not in starch but in inulin, a polymer of fructose. Unlike other starchy staples, bananas are fruits. Sweet bananas are often considered a dessert or snack food, but starchy plantains are important as food in the tropics, where they are traditionally cooked and eaten as a vegetable.