Sugar crops are plants that are natural sources of the sweet substance called sugar in large quantities. These natural sweeteners are found in or extracted from different organs such as the roots of sugarbeet, tubers of Jerusalem artichoke, the stems of sugarcane, sorghum, and sugar maple, inflorescences of certain palms, the grains of corn, and many fruits (Hill 1972).
Table 1. List of sugar crops that are major sources of various types of sugar.
|Common Name||Scientific Name||Family Name|
|Sources of Sucrose|
|Sugarcane||Saccharum officinarum||Poaceae / Gramineae|
|Sugarbeet||Beta vulgaris||Chenopodiaceae / Amaranthaceae|
|Sugar maple, Maple tree||Acer saccharum||Aceraceae|
|Black maple, Black sugar maple, Hard maple, Rock maple||Acer nigrum||Aceraceae|
|Sweet sorghum, sorgo||Sorghum bicolor||Poaceae / Gramineae|
|Palms (various names)||various species||Arecaceae / Palmae|
|Sources of Glucose|
|Corn, maize (corn syrup or crystallized corn sugar from starch)||Zea mays||Poaceae / Gramineae|
|Potato, White potato (from starch)||Solanum tuberosum||Solanaceae|
|Sources of Fructose|
|Dahlia (from inulin)||Dahlia pinnata||Asteraceae|
|Jerusalem artichoke, sunchoke, sunroot (from inulin)||Helianthus tuberosus||Asteraceae|
|Corn, maize (high-fructose corn syrup from starch)||Zea mays||Poaceae / Gramineae|
|Sources of Galactose|
|Flax, Linseed (from flaxseed gum or mucilage)||Linum usitassitimum||Linaceae|
|Sources of Mannose|
|Ivory nut, Ivory nut palm (from endosperm)||Phytelephas macrocarpa||Arecaceae / Palmae|
|Manna ash tree, Flowering ash (from juice secreted through the bark)||Fraxinus ornus||Oleaceae|
|Sources of Maltose|
|Barley||Hordeum vulgare||Poaceae / Gramineae|
|Rice||Oryza sativa||Poaceae / Gramineae|
Besides these sugars, there are sugar alcohols such as sorbitol, mannitol, and xylitol which are also considered nutritive sweeteners because they provide energy to consumers along with sweetness. They have the relative sweetness of 0.6, 0.7, and 0.9, respectively, and are thus less sweet than sucrose which, for comparison, is presumed to have a relative score of 1 (Wardlaw et al. 2004).
These sugar alcohols are derivatives of monosaccharides after one or more functional groups are altered through chemical reactions. The reduction product of D-glucose is D-gluticol which is popularly called D-sorbitol, D-galacticol for D-galactose, and so forth (Bettelheim and March 1998). Sorbitol is prepared by hydrogenation of glucose under high pressure over a nickel catalyst (Carey 1992).
Further, there are alternative sweeteners, also called artificial sweeteners, which provide little or no energy. These include the cyclamate, aspartame, acesulfame-K, saccharin or sodium salt, sucralose, and neotame which have relative sweetness scores of 30, 180, 200, 300, 600, and 7000-13000, respectively, meaning that their sweetness range from 30 times to 13,000 times more than that of sucrose. However, the use of cyclamate was banned in the United States in 1970 despite the absence of conclusive proof that it can cause health problems when properly used. But in Canada, it is also used as a table-top sweetener (Wardlaw et al. 2004).
In addition, stevia (Stevia rebaudiana), a shrub of South American origin, has been suggested as a potential replacement for conventional sugar crops. Its sweetening compound is a diterpene glycoside called stevioside which is 100 to 300 times sweeter than ordinary sugar (Lyakhovkin et al. 1993 cited by Lantican 2001; Wardlaw et al. 2004). But it provides no calories. As of 2004 according to Wardlaw et al. (2004), stevia was on sale in health-food outlets in the United States as a dietary supplement.
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