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1. Functional and
prebiotic foods
2. Soy and broad beans
3. Fibre, oligosaccharides
and proteins
4. Antecedentes y
contribuciones previas del grupo
1. Functional and prebiotic foods
The concept of "functional food" was firstly
introduced in Japan around the middle of 1980s (Hasler, 1998; Van
der Broek, 1993) and it
was defined as the food consumed in the usual diet with a proved
benefit for health or able to prevent diseases. Compounds capable of
stimulate a selective growth of health beneficial bacteria from
colon are considered "prebiotics" (Gibson and
Roberfroid, 1995).
The word "probiotic" is used to name dietetic
supplements with a microbial origin, such as bifidobacteria or
lactobacilli. These bacteria are very sensitive to pH changes
produced during digestion, and many of them die before reaching the
colon. Because of that, it is better to add prebiotic compounds to
foods, as it is technologically easier and its beneficial effect on
the body is longer.
National and International Institutes of Health (US Department
of Health and Human Service, 1990) recommend society to increase the
intake and variety of vegetable foods, in order to prevent common
diseases such as cardiovascular problems and different types of
cancer. A daily intake of five or more pieces of fruits and
vegetables is advised, depending on the age of population (Russell,
1999).
2. Soy and broad beans
Soy bean and its products are part of the main Eastern diets and
nowadays their consumption has increased in Western countries
because of their nutritional value and beneficial influence on
health. A wide bibliography about soy bean has been published but
the specific components responsible of the attributed beneficial
effects are unknown. Broad beans are especially consumed in
Mediterranean countries.
The consumption of vegetable foods has been associated with the
prevention of some chronic diseases such as cataract, vascular
pathologies and several types of cancer (Halliwell, 19997, Beecher,
1999). Between the different properties attributed to soy bean
the anti-cancer capacity and the beneficial action in
cardiovascular diseases, diabetes and obesity, can
be mentioned (Messina, 1995; Lee et al., 1996; Than et al., 1998; Anderson
et al., 1999).
On the other hand, soy bean also has an important place as a
functional product due to its anti-cholesterol properties (Sirtori
et al., 1999). According to Lovati et al. (2000), the
reduction of total cholesterol is caused by a stimulation of LDL
hepatic receptors, induced by soy bean proteins and peptides.
Raw materials have been selected by their potentiality as a source
of prebiotic compounds for obtaining oligosacharides, fibre and
proteins. Two vegetables were used as model and comparative system:
soy bean seeds (Glycine max), fresh broad beans (Vicia
faba) and by-products of soy (soywhey and okara) from the
preparation of soy drink (soy milk) and tofu, and from the broad
beans pods. Both vegetables are rich in fibre and oligosacharides
allowing us to compare a product from Mediterranean with
another from Eastern diet.
3. Fibre, oligosaccharides and proteins.
Legumes are rich in carbohydrates and proteins.
Soy and broad beans are a good source of soluble and insoluble fibre..
The oligosaccharides from broad and soy beans are a-galactosides
(Saito et al., 1992), also known as oligosaccharides from the raffinose family or
galacto-oligosaccharides, which can be considered
derived from the sucrose by addition of galactose molecules and can
be obtained by solubilization. Broad bean seeds contain particularly
a penthasaccharide named verbascose, while in other legumes the
main galactosides are raffinose (trisacharide) or estachyose (tetrasaccharide)
(Rupérez, 1998; García-Domingo et al., 1997). With regard to
the oligosaccharides and fibre contained in the waste from broad beans
or by-products from the tofu industry, no references
have been found.
Non absorbed fibre and oligosaccharides are indigestible or
resistant carbohydrates (Cumming et al., 1997) and they are
considered prebiotics because of their capacity to stimulate the
selective growth of colon bacteria with beneficial effects on health
(Gibson and Roberfroid, 1995). As they are not digested through the
human digestive tube, they reach colon without degradation and are
fermented there by saccharolitic bacteria, which use carbohydrates as
energy source.
The importance of soy bean proteins is based on their physical
and chemical properties (gelificant, emulsionant, foaming, elasticity,
viscosity, solubility, cohesion-adhesion, water and fat absorption,
etc). These properties can be modified by the conditions of
preparation of the products. The essential aminoacids contained in
proteins from soy bean is different from the one in cow-milk, because
the first one has a smaller amount of methionine and phenilalanine;
however it is considered a complete protein. The reserve proteins in
soy bean are albumins and mainly globulins. Glycine and b-conglycinine
(globulins) have different structure and properties with a
remarkable capacity to form gels. Such characteristic is the base to
one of the most traditional products in Eastern diets, the tofu (a
soy protein concentrate).
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