Agriculture Reference
In-Depth Information
temperature or power microwave drying and rehydration temperature using response
surface methodology.
I
NTRODUCTION
Dietary fiber are usually defined as 'ingredients of plant cells which are resistant to
digestive enzymes of man', however this definition is general and does not include the
physical characteristics of the individual components of dietary fiber, and does not disclose
all of the physiological effects that are associated with the action of the fibers in the body, so
that in practical work total dietary fiber defined as 'values obtained by AOAC analytical
method (AOAC 1995, method 985.29)'. This definition of dietary fiber include major
constituents of food, such as cellulose, hemicellulose, lignin, gum, modified cellulose, mucus,
oligosaccharides and pectin, and associated ancillary components such as wax, kutina and
suberin (DeVries et al., 1999). There are numbers of dietary fiber classifications that are
based on their different characteristics. According to Stauffer (1993) dietary fiber can be
divided into two groups: insoluble dietary fiber (cellulose, lignin, resistant starch products of
Maillard's reaction, and other materials of vegetable origin) and soluble dietary fiber, mucus
that may be endogenous and exogenous origin
.
Until recently it was thought that the fibers pass through the digestive tract without any
importance in the diet, and was designated as ballast matters. However, beneficial
physiological effect of fiber is determined; so much research in medicine is directed toward
defining the physiological mechanisms of dietary fiber action (Wisker et al. 1985, Stauffer
1993, Reickhoff et al., 1999). Dietary fibers bind bile acids and cholesterol, preventing their
reabsorption. High concentrations of bile acids in the intestine, especially secondary bile
acids, increases the risk of intestine cancer. Dietary fiber lowers cholesterol levels in the
blood, and thus the possibility of blood vessels blocking. It was found that dietary fibers have
good effect on the micro flora of the colon. Fibers water and various cancer metabolism
products (products of oxidation of fatty acids, amines, phenolic) binding properties increase
the weight of the feces, accelerating the digestive tract discharge, thereby reducing the
possibility of cancer. In addition, the use of fibers in diet may lower frequency of formation
of hemorrhoids, bleeding and inflammatory processes in the intestine.
A particular physiological effect of dietary fiber exerts a slowing of gastric passage,
which increases the feeling of satiety, and therefore foods rich in dietary fiber limits the need
for calories (Pribiš 1999). The negative effects of consuming foods rich in dietary fiber are
mainly related to the initial period of use of such food (soft stool, diarrhea), and it disappears
after a few days. Tolerance to dietary fiber, in general, is good, but in order to eliminate any
possible negative effects, for the organism to adopt the products rich in fiber it is necessary
that intake should be increased gradually (Thibault 1994).
The main sources of dietary fiber are the cell walls of plants, i.e., fresh or dried fruits and
vegetables, and grain cultures. Nowadays, significant sources of dietary fiber are industrial
plants that contain a high percentage of fiber. The richest sources of dietary fiber from fruits
are: apples, oranges and bananas; vegetables: cauliflower, carrot, potato, tomato, boiled sweet
corn, and various types of lenses, beans, green beans and peas; of products based on cereals
and legumes commonly referred as bran it is all kinds of grain, with special emphasis on oat
