Galactooligosaccharides (GOS),  belong to the group of prebiotics. Prebiotics are defined as non-digestible food ingredients that beneficially affect the host by stimulating the growth and/or activity of beneficial bacteria in the colon. GOS occurs in commercially available products such as food for both infants and adults.

In nature, there are trace amounts of galacto-oligosaccharides in animal milk, and the content is slightly higher in breast milk. Galacto-oligosaccharides have a relatively pure sweet taste, low calorific value, and a sweetness of 20% to 40% of sucrose, and are extremely moisturizing. They have high thermal stability under neutral pH conditions, and there is no decomposition of galacto-oligosaccharides after heating at 100°C for 1 hour or at 120°C for 30 minutes. When galacto-oligosaccharides are heated together with proteins, the Maillard reaction will occur, and they can be used in the processing of foods with special properties such as bread and cakes.

Stimulating bacteria

Galactooligosaccharides are a substrate for bacteria, such as Bifidobacteria and lactobacilli. Studies with infants and adults have shown that foods or drinks enriched with galactooligosaccharides result in a significant increase in Bifidobacteria. These sugars can be found naturally in human milk, known as human milk oligosaccharides. Examples include lacto-N-tetraose, lacto-N-neotetraose, and lacto-N-fucopentaose.

Immune response

Human gut microbiota play a key role in the intestinal immune system. Galactooligosaccharides (GOS) support natural defenses of the human body via the gut microflora, indirectly by increasing the number of bacteria in the gut and inhibiting the binding or survival of Escherichia coli, Salmonella typhimurium and Clostridia. GOS can positively influence the immune system indirectly through the production of antimicrobial substances, reducing the proliferation of pathogenic bacteria.

Constipation

Constipation is a potential problem, particularly among infants, elderly and pregnant women. In infants, formula feeding may be associated with constipation and hard stools. Galactooligosaccharides may improve stool frequency and relieve symptoms related to constipation.