POLYSACCHARIDES – WHOLE GRAINS ARE HEALTHIER PART 1
Polysaccharides are complex glucides whose molecule is formed by the union of several monosaccharides. They are mainly found in cereals, legumes, leaves, roots and tubers.
STARCH is one of the most widespread poliglucides in nature, being also the most important source of glucides for humans and animals. Starch is the product of photosynthesis process in green plants. Most starch is found in cereals: rice 70-80%, wheat64-70%, corn 60-66% and potato tubers 14-25%.
Raw starch is not digestible, as is found encapsulated as granular form, whose configuration and size is a property of each plant species. The starch granules size is between 20 and 100 millimicrons. Through boiling or baking, the starch granules are gelatinized and the starch becomes digestible.
In terms of chemical composition starch is a mixture of 2 poliglucides: amylose and amylopectin. Amylose is found inside the starch granule and is soluble, and amylopectin is found in the granules wrapping, being difficult soluble.
The enzyme called ptyalin, in the saliva, dissolves the starch from: cereals, potatoes, vegetables and herbs, into maltose, which is composed of two molecules of glucose. Ptyalin is inactivated if the stomach acid is bigger than pH 4. As long as the gastric pH doesn’t decreases under 4, the starch digestion in the stomach can continue. Animals proteins raise the gastric acidity, so prevents the starch digestion stomach. Instead, for the digestion of proteins from cereals, potatoes and vegetables do not need a highly acidic environment, so they are an ideal partner for fruits and vegetables.
But careful with nuts which, in large quantities, increases the gastric acidity.
In the small bowel the starch digestion is made, which is gradually disolved in component glucose molecules and that, absorbing itself provides the necessary fuel that the body needs without flooding the bloodstream with an excessive amount of glucose, which happens if we ingest simple glucides. Athletes, who are forced to prolonged physical effort, they have understood the starch benefits as a continuous source of energy, which is why, for example, tennis players, instead of steaks, have a cereal products meal.
Scientists are convinced that, in the third millennium, the feeding of world population will not be possible without the help of cereals and potatoes. Unrefined cereal products contain sufficient quantities of proteins, essential fatty acids, vitamins, antioxidants, iron, calcium, selenium, zinc and everything our body needs for developing and maintaining health. In a recent study, professor J. Slavin at the University of Minnesota, USA, sustain that for improving the alimentation and health, americans must use more whole cereal products. And, as Hrusciov was saying, what’s good for Americans is good for us too.
The wheat grain, for example, consists of endosperm composed of starch, germ, which contains proteins – about 12-14% – fats, antioxidants and outer layer, known as bran. Approximately 50-80% of grain minerals, including copper, zinc and magnesium are found in the bran. The germ is rich in unsaturated fats and natural antioxidants for those fats.
The overwhelming majority of published studies in recent years shows that a predominantly whole cereales alimentation lowers the risk of cancer diseases. The protective role of cereales is done by several mechanisms.
First, the presence of fermentable glucides. Whole cereals are rich sources of alimentation fibers, resistant starch and oligosaccharides. Fermentation of carbohydrates in the intestine produces fatty acids with short chains, as acetate, butyrate and propionate, lowering the colic pH.
Butyrate serves as a preferred source of energy for intestinal mucosa cells and has an anticancer action. The smallest are the grains ground, the greater is the concentration of faecal butyrate, suggesting a stronger bacterial action. Adding of whole grain to bread has no effect.
The resistant starch is fermented also by the bacteria that are present naturally in intestine.