Gellan gum comes in two forms: high acyl (HA) and low acyl (LA), and their gels exhibit different properties.

High Acyl (HA) Gellan Gum:

  • Gel Formation: HA gellan gum forms soft, elastic, and thermoreversible gels.
  • Thermoreversibility: These gels can transition between a gel state and a sol (liquid) state depending on temperature. As the gel cools, it forms; when reheated, it melts back into a liquid. This makes HA gellan gum ideal for applications where a reversible gel structure is required.

Low Acyl (LA) Gellan Gum:

  • Gel Formation: LA gellan gum forms firm, brittle, and non-thermoreversible gels.
  • Thermoreversibility: Unlike HA gellan gum, gels formed by LA gellan gum do not revert back to a sol when reheated. Once the gel is formed, it remains stable even at higher temperatures, making it non-thermoreversible. This property is useful in applications where a permanent gel structure is desired.

Key Differences:

  • Reversibility:
    • HA Gellan Gum: Forms thermoreversible gels.
    • LA Gellan Gum: Forms non-thermoreversible gels.
  • Texture:
    • HA Gellan Gum: Produces soft and elastic gels.
    • LA Gellan Gum: Produces firm and brittle gels.
  • Application:
    • HA Gellan Gum: Suitable for products where gel stability is needed under varying temperature conditions.
    • LA Gellan Gum: Suitable for products that require a stable gel structure at higher temperatures.

there are several other important differences between high acyl (HA) and low acyl (LA) gellan gum beyond their thermoreversibility and gel texture:

1. Ionic Sensitivity:

  • LA Gellan Gum: Requires the presence of cations (like calcium, magnesium, or potassium ions) to form a gel. The concentration and type of cations influence the gel's strength and texture. Higher ion concentrations typically result in firmer gels.
  • HA Gellan Gum: Less dependent on cations for gel formation. It can gel in water without the need for added ions, which makes it more versatile in different formulations.

2. Gel Strength:

  • LA Gellan Gum: Forms much stronger gels compared to HA gellan gum. The gel strength increases with the concentration of gellan gum and the presence of cations. This is why LA gellan gum is often used where a firm and brittle texture is desired, such as in certain food products or industrial applications.
  • HA Gellan Gum: Forms softer and weaker gels. The gels are more elastic and flexible, which can be desirable in applications requiring a softer mouthfeel or texture.

3. Hydration and Dissolution:

  • LA Gellan Gum: Requires higher temperatures (typically around 80-90°C) to fully dissolve in water. Proper dissolution is essential to achieve consistent gelation.
  • HA Gellan Gum: Hydrates and dissolves more easily at lower temperatures (around 60-70°C). This makes it easier to work with in formulations that are sensitive to high temperatures.

4. Clarity:

  • LA Gellan Gum: Forms clear gels, which is important for applications where transparency is desired, such as in certain beverages, desserts, or encapsulated flavors.
  • HA Gellan Gum: The gels formed are often more opaque, which might not be suitable for applications requiring visual clarity.

5. Synergy with Other Hydrocolloids:

  • LA Gellan Gum: Can be combined with other hydrocolloids like xanthan gum, guar gum, or locust bean gum to modify the gel texture and stability. These combinations can improve the elasticity, reduce syneresis (water release), and alter the gel strength.
  • HA Gellan Gum: Also shows synergy with other hydrocolloids, but the combinations typically aim to adjust the softness and flexibility of the gel rather than just its strength.

6. Applications:

  • LA Gellan Gum: Often used in applications where a firm, stable, and clear gel is required, such as in jelly desserts, plant-based meats, or encapsulated flavor systems.
  • HA Gellan Gum: Preferred in applications that require softer, more elastic gels, such as in certain dairy products, soft gels, and spreads.

Summary of Key Differences:

  • Ionic Sensitivity: LA requires ions; HA does not.
  • Gel Strength: LA forms stronger gels; HA forms softer gels.
  • Hydration: LA needs higher temperatures to dissolve; HA dissolves at lower temperatures.
  • Clarity: LA gels are clear; HA gels are more opaque.
  • Synergy: Both types work with other hydrocolloids but with different textural outcomes.
  • Applications: LA is used in firmer, clearer products; HA is used in softer, more elastic products.

These additional differences highlight the versatility of gellan gum in various applications, depending on whether you use the high acyl or low acyl form.