Microbial Hydrocolloids Redefining Food Consistency

Microbial hydrocolloids are a vital component of the food industry, derived from the fermentation of microorganisms. These hydrocolloids possess unique rheological properties, making them suitable for various food applications. They are used as functional ingredients in food formulation for increasing food consistency, improving the gelling effect, and controlling the microstructure, texture, flavour, and shelf life. This article discusses three types of microbial polysaccharides-based hydrocolloids: Xanthan gum, Gellan gum, and Pullulan gum.

Xanthan gum (INS 415), produced by the bacterium Xanthomonas campestris, has a cellulosic backbone of β-glucose units substituted with a trisaccharide side chain. The side chain consists of two mannose units separated by glucuronic acid, with approximately half the terminal mannose units linked to a pyruvate group. Xanthan gum’s molecular structure allows it to form highly viscous solutions and exhibit weak gel-like properties and excellent thermal stability, making it suitable for use in watery food products.

Gellan gum (INS 418), produced by the microorganism Sphingomonas elodea, is a fermentation polysaccharide with a molecular structure based on repeating glucose, rhamnose, and glucuronic acid units. In its native form, gellan gum contains acetate and glycerate substituents, while low-acyl gellan gum lacks these substituents. Upon cooling, gellan solutions can form double helices that aggregate into weak gel structures, which can be strengthened by the presence of appropriate cations like K+, Na+, Ca++ Mg++. However, acyl substituents in native gellan interfere with aggregation, resulting in weaker gels. Due to the ability to form microgels and films, it is used for binding to the nutrient surface and as a coating material.

Pullulan gum (INS 1204), produced by many species of the fungus Aureobasidium, is a water-soluble homopolysaccharide of glucose with (1→4) and (1→6)-linked α-D-glucopyranosyl residues. The ratio of (1→4) to (1→6) linkages is 2:1, and pullulan is built up of maltotriose units linked by (1→6) with smaller amounts of maltotetraose units. The presence of (1→6) glycosidic linkages increases Pullulan’s flexibility and solubility in water compared to other linear polysaccharides like amylose starch. Pullulan easily dissolves in cold or hot water to form a stable, viscous solution that does not gel and is stable over a wide range of pH and heat. Pullulan gum film is clear, colourless, odourless, non-toxic, hard, very oil resistant, and edible and can be used for food packaging. It has important applications as adhesive ingredients for the pharmaceutical capsule and cosmetics industry, food quality improvers and thickeners, water-soluble packaging material to prevent oxidation, and low-calorie food raw materials for staple foods and sweets.

In conclusion, microbial polysaccharides-based hydrocolloids offer unique rheological properties that make them ideal for various food applications. Xanthan gum forms highly viscous solutions and exhibits weak gel-like properties, making it suitable for watery food products. Gellan gum is widely used as a thickener and stabilizer in the food industry, while pullulan has excellent film formation, fibre formation, and gas barrier properties, making it widely used in medical, food, and light industry, chemical and petroleum fields. Further research is needed to explore the potential applications of these hydrocolloids in different fields.