Gellan gum is a polysaccharide whose origin differs from that of other hydrocolloids presented so far. Its rather recent discovery was the result of industrial research on gum from bacterial fermentation. Sphingomonas elodea bacteria transform simple sugars, phosphate, nitrogen and nutrients into chains of more complex sugars. Once the process has been completed, the microorganisms are eliminated by pasteurization.
Precipitation in alcohol and acyl group clarification or elimination processes are applied to the gum to further transform it. Four derivatives are manufactured in the industry, each with different properties. Two forms are more widely used in cooking: high-acyl and low-acyl gellan gum.
HIGH-ACYL GELLAN GUM produces a supple, elastic texture, which is the result of the well-known acyl groups, allowing the formation of helices that trap water. Upon hydration, the gum is insensitive to the presence of calcium or sodium ions, which do not significantly affect the formation of a gel. However, heat is necessary to properly hydrate the molecule, whereas the presence of sugars or acids in excessive quantity can interfere with this crucial step. The gel melts and re-sets at about 158°F to 176°F (70°C to 80°C).
LOW-ACYL GELLAN GUM is more commonly used in molecular gastronomy to make firm, brittle gels that tolerate temperatures up to 284°F (140°C). For this reason, it is preferred in the preparation of hot dishes. However, it must be handled with great care, as it is significantly more sensitive to the presence of ions than its high-acyl counterpart. Hard water, as well as the presence of sugar or an acid solution medium, slows down the hydration process, which requires a higher temperature.
The best way to properly hydrate this product is to mix it with demineralized water or milk, or use sequestering agents and mix vigorously. The sequestering agents used are salts (sodium citrate, sodium hexametaphosphate) which, when dissolved in water, attach to the ions, making them unavailable for the gum in the solution and thus allowing it to hydrate at a lower temperature. The gel forms upon cooling due to the ions present in the food added to the mixture, or by the addition of other ions such as calcium, sodium, magnesium or potassium salts. There are a great variety of solutions with which low-acyl gellan gum can form gels, which greatly increases its possible uses.
Did you know?
GELLAN GUM replaces agar-agar in culture media that must be maintained at very high temperatures.
GELLAN GUM is used in gelatinous beverages that are popular in Asia, but marketing abroad proved to be difficult, particularly in North America with the beverage “Orbitz.”
GELLAN GUM adheres salt crystals that are sprayed onto pretzels, without adding fat.
GELLAN GUM often replaces pectin in sugar-free jams and is added to dry cake mixes to maintain enough moisture during cooking.