Starch-containing plants maize

The polysaccharide starch is found in most plants as a storage compound however, only five plants, namely maize, rice, wheat, potatoes, and cassava account for the majority of worldwide produced starch-containing plants. Roughly 2.7 billion tons of these crops are annually harvested. The class of sugar-containing crops contains only two plants namely sugar cane and sugar beet of which about 2 billion tons are... 

Starches of the various plants differ with respect to their proportions of amylose and amylopectin. For example, the starch in com (maize) of the variety most commonly grown in the United States contains 26% of amylose and 74% of amylopectin. Some other varieties of com contain starches that are substantially 100% amylopectin, and there are others having amylose contents of 80 to 85%. 

Statches ftom different plant sources differ in their amylose/ amylopectin ratio. For example, com starch contains about 27% amylose, potato starch about 22%, and tapioca statch about 17%. In contrast, waxy com statch contains almost entirely amylopectin, with no amylose. These diffetences modify the physical properties of the statches such that the various types may not be interchangeable in a given pharmaceutical application. For example, amylose-rich maize starch has been studied as a potential tablet film-coating ingtedi-... 

Waxy com starch, also known as waxy maize starch, consists of only amylopec-tin molecules, giving this starch different and useful properties (see Chapter 3). This genetic variety of com was discovered in China in the early 1900s, when com plants were transferred from the Americas. The starch stains red with iodine, not blue as ordinary starches do. When the com kernel is cut, the endosperm appears shiny and waxlike, and the com was termed waxy com or waxy maize. However, it contains no wax. 

The most common sources of starch in various regions of the world are potato, maize, cassava (manioc, tapioca, yucca), and rice. Popularity of a given starch and starchy plants do not go together. For instance, in many regions of the world wheat and rye are very commonly used. Wheat starch is only randomly isolated, and rye starch is only exceptionally available. Rye grains contain mucus, which seriously obstructs isolation of starch from this source. 

Starch is prepared on the industrial scale from the parts of those plants in which it occurs in greatest abundance. The seeds of the cereals contain starch as their principal ingredient. Wheat contains 55 to 65 per cent. barley, 38 to 46 per cent. oats, 28 to 38 per cent. rye, 44 to 47 per cent. maize, 54 to 67 per cent. rice 70 to 76 per cent. potatoes, 16 to 23 per cent. 

Lactic acid used in the preparation of PLA is derived from annually renewable resources. Cargill Dow uses sugar from maize as feedstock, due to its low cost and abundance, but it is envisaged to use local plant sources containing starch, or sugar, such as wheat, sugar beets or agricultural waste (Fig. 2.5). 

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