Carbohydrate, any of a large group of compounds in which hydrogen and oxygen, in the proportions in which they exist in water, are combined with carbon; the formula of most of these compounds may be expressed as Cn(H2O)n. Structurally, however, these compounds are not hydrates of carbon, as the formula would seem to indicate.
Carbohydrates, as a class, are the most abundant organic compounds found in nature. They are produced by green plants and by bacteria using the process known as photosynthesis, in which carbon dioxide is taken from the air by means of solar energy to yield the carbohydrates as well as all the other chemicals needed by the organisms to survive and grow. They provide most of the energy to support our daily activities and have about 4 kcal/g (17 kJ/g) (“Carbohydrates”, 2007).
Carbohydrates that cannot be broken down to lower molecular weig ht carbohydrates by hydrolysis are monosaccharides, a term that indicates that they are the monomeric building units of the olig o- and polysaccharides. Monosaccharides are commonly referred to simply as sug ars. They can be joined together to form larger structures, namely, oligosaccharides and polysaccharides that can be converted into monosaccharides by hydrolysis. They vary in the number of carbon atomspresent in their structure. Table 1.1 shows the classification of monosaccharides (Fennema, 1996).
Table 1.1. Clasification of Monosaccharides.
| |Kind of carbonyl group |
|Number of carbon |Aldehyde |Ketone |
|atoms | | |
|3 |Triose |Triulose |
|4 |Tetrose |Tetrulose |
|5 |Pentose |Pentulose |
|6 |Hexose |Hexulose |
|7 |Heptose |Heptulose |
|8 |Octose |Octulose |
References: BELITZ HD and GROSCH W. 2009. Food Chemistry. Germany: Springer-Varleg.
DE MAN JM. 1999. Principles of Food Chemistry 3rd ed. Maryland: Aspen Publishers, Inc.
FENNEMA OR. 1996. Food Chemistry 3rd ed. New York: Marcel Dekker.
Carbohydrates. 2007. Microsoft Encarta 2007 [DVD]. Washington: Microsoft Corporation.
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