Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
20.6.2 OTHER EFFECTS OF FIBER
Fiber has other effects besides adsorbing minerals. A number of papers have reported
the positive and negative action of fiber. FOS influence homeostasis of cells in the
intestine walls and protect them. Immunomodulation and bacteriostatic activity
should also be considered. The activity might result from blocking receptors capable
of interactions with pathogenic bacteria. Oligosaccharides with mannose side-chains
obstruct adhesion of Escherichia coli to the intestinal walls. Cellobiose, the plant
disaccharide, reduces infectivity of Listeria monocytogenes. FOS added to animal
fodder significantly decrease frequency of the colon cancer. Recommended daily
uptake of FOS for humans reaches 4 g. In rats, inulin also inhibits production of
carcinogenic sialomucins and stimulates synthesis of anticarcenogenic sulfomucins.
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A fiber-rich diet increases fecal bulk, making the stools softer and more frequent.
A high volume of unabsorbed food shortens the transit time and lessens the concentration
of carcinogens, reducing their contact with intestinal walls.
Other less beneficial side-effects have been reported. Pectins in fiber added to
naturally occurring food pectins can exceed the natural level and cause diarrhea.
Nonfiber saccharides such as raffinose and stachyose present in legume plants
are not digested by the human enzymatic system. Their bacterial digestion, similar
to the effect of excessive fiber, produces flatulence.
20.7 ORGANOLEPTIC PROPERTIES OF SACCHARIDES
Carbohydrates are commonly appreciated for their organoleptic properties. They add
sweet taste, flavor, color, and texture to foodstuffs. The organoleptic properties
resulting from the presence of carbohydrates strongly affect cephalic phase of food
intake.
There are also adverse effects of modification of carbohydrates on food processing
and digestion. These problems are important in case of thermally processed milk
monodiet for suckling children. Carbohydrates react with lysine into dihydroalanine,
provoking the degradation of cystine and forming lysinoalanine. This type of reaction,
called Maillard reaction (Chapter 18), decreases nutritional value of food by
reducing essential amino acids and vitamins. Thermal processing of milk leads also
to epimerization of lactose to nondigestible lactulose. A decrease in lactose concentration
not only changes palatability and flavor of milk, influencing the volume of
ingested food, but also decreases the available energy, declines calcium absorption,
reduces intestinal pH, and lowers bioavailability of galactose, essential for proper
brain development.
20.8 NONNUTRITIONAL SACCHARIDES
Some saccharides are important constituents of medicines, such as cardiac glycosides,
aminoglycosides (antibiotics), and artificial heparin widely used as an anticoagulant.