Until recently, it was believed that all the starch from foods is easily digested and absorbed by the small bowel.

Recent studies have shown that some of the starch ingested is resistant to the hydrolysis of human digestive enzymes. In other words, a fraction of the starch consumed through cereal products, vegetables, potatoes it is not digested by our enzymes and, therefore, can not be absorbed.

All recent studies have shown that in the human intestine, this starch has similar actions with food fibers, formerly known as ballast substances.

Starch is a simple mixture of two glucose polymers: amylose and amylopectin.

Today, foods that contain starch are classified as: those that are digested quickly in the small bowel of human, those that are digested slowly and those that resist to digestion in the small bowel.

Resistant starch is defined as the sum of starch and the products resulted from its digestion, that are not absorbed in the small bowel of a healthy person.

This resistant starch can be classified into 3 types:

Type 1 is inaccessible for the hydrolysis in the small bowel because it’s protected by amylase action through the integrity of cell walls or other structures. This type of starch is present in cereals products that contain whole grains or pieces of grains partially ground and in vegetables.

Type 2 or native starch. It is known that the raw potato starch is not digested in the small bowel of animals and man.

Interesting is that the raw wheat starch is digested easily by the human amylase but the potato starch can not. The exact mechanism of this resistances towards the human digestive enzymes is not clear, but seems that depends of a number of factors, such as grains size of starch, the ratio between the amorphous and crystalline material, polysaccharide architecture and the ratio between amylose and amylopectin.

Each plant has its characteristic starch granules.

Cereales have small grains with a diameter between 1 and 30 microns being spherical or polyhedral. In potatoes and bananas, the starch granules are large and oval with a diameter of 10-80 microns, being smooth.

Larger area versus volume can make the grains starch more digestible than potato grains. In other words, the cereal starch granules present a larger area of ​​attack for the digestive enzymes, leading to a better digestibility.

The starch granules ground mechanical during the preparing course are more digestible.

But the polysaccharides starch granules architecture is different too, making the bigger digestibility to have it cereals starch, followed by legumes starch, on the third place being the potato.


Categories: Diet, Health, Nutrition

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