Introduction to Oligosaccharides

In the previous article, we briefly introduced common oligosaccharides and their wide range of applications. In this issue, the editor will further explore the definition, classification, mechanism of action and functional oligosaccharides.

1. Definition

There are several main ways to define oligosaccharides.

1. Oligosaccharides are carbohydrates that are hydrolyzed into 3 to 8 monosaccharide molecules per molecule. Some people also classify carbohydrates that are hydrolyzed into 3 to 10 or even 20 monosaccharide molecules into this category.

2. Oligosaccharides refer to the general term for carbohydrates whose molecular structure is composed of 2-10 monosaccharide molecules connected by glycosidic bonds.

3. Oligosaccharides, from maltotriose to maltooctaose, are all α, D-glucose bonded by α-1→4 and α-1→6 glycosidic bonds. The structure of hetero-oligosaccharides is relatively complex. The molecular weight is 300-2000, between monosaccharides (glucose, fructose, galactose) and polysaccharides (fiber, starch), and there are disaccharides, trisaccharides, and tetrasaccharides.

4. It is a small molecule polysaccharide composed of 3-10 monosaccharides.

5. Generally, oligosaccharides are a combination of 2-10 monosaccharides connected by glycosidic bonds, combinations of more than 11 monosaccharides are called macrosaccharides, and combinations of 100-2000 monosaccharides are called polysaccharides.

2. Classification

1). All sugar molecules produced by hydrolysis are glucose, which are called maltooligosaccharides. Those composed of three glucose molecules are called maltotriose, those composed of four glucose molecules are called maltotetraose, and so on.

2). When hydrolyzed, more than one monosaccharide is produced, which is called hetero-oligosaccharide. For example, the hetero-oligosaccharide in soybeans is hydrolyzed to produce raffinose and stachyose, which are difficult for humans to digest and cannot be used. However, the hetero-oligosaccharides synthesized by the body itself have very important physiological functions.

3. Mechanism of action

Functional oligosaccharides have physiological functions because they can promote the proliferation of bifidobacteria, the beneficial bacteria inherent in the human intestine, thereby inhibiting the growth of putrefactive bacteria in the intestine and reducing the formation of toxic fermentation products.

Due to the high sensitivity of bifidobacteria to oxygen, force, heat and acid, it is quite difficult to add it directly to food, but this is easy for oligosaccharides.

4. Distribution

Only a few plants in nature contain natural functional oligosaccharides. For example, onions, garlic, silvergrass, asparagus, chicory root and artichokes contain oligofructose, and soybeans contain soy oligosaccharides.

Oligosaccharides have similar properties to monosaccharides: crystallinity, sweet taste, easy to dissolve in water, difficult to dissolve or insoluble in organic solvents. Some are reducing, such as maltose, lactose, and mannotriose, while others are non-reducing, such as sucrose and gentiotriose.

5. Functional Oligosaccharides

Oligosaccharides with special physiological functions or special uses, such as maltotriose and maltotetraose, are common oligosaccharides. They can be digested and absorbed by the body, but are not proliferation factors for the beneficial intestinal bacteria Bifidobacterium.

Functional oligosaccharides include stachyose, raffinose, isomaltulose, lactulose, fructooligosaccharides, xylooligosaccharides, galacto-oligosaccharides, lactofructooligosaccharides, isomaltulose, isomaltulose and gentio-oligosaccharides, etc.

There is no enzyme system in the human gastrointestinal tract that can hydrolyze these oligosaccharides (except isomaltulose), so they are not digested and absorbed but directly enter the large intestine to be preferentially utilized by bifidobacteria, acting as proliferation factors for bifidobacteria.

Among them, except for oligogentiosaccharides which have no sweetness but bitter taste, the rest have sweetness to varying degrees and can be used as functional sweeteners to replace or partially replace sucrose in food.

Because of its special bitter taste, gentiooligosaccharide can only be used in foods such as coffee drinks and chocolate and as a flavor enhancer for certain special seasonings.