FAQs

What is the relationship between the gel properties of low-acyl gellan gum and calcium ion concentration?

The following is a systematic data analysis based on experimental validation, illustrating the influence of calcium ion concentration on gel transparency, color, and gel strength in a 0.3% low-acyl gellan gum system.

I. Experimental Design

• Gellan gum concentration: 0.3% low-acyl gellan gum (food/microbiological grade)

• Calcium source: Lactate calcium solution (ensuring complete dissolution)

• Tested calcium concentration gradient: 0.00% (control), 0.06%, 0.08%, 0.10%, 0.15%, 0.20% (based on the total mass percentage of calcium ions in the system)

• Preparation method:

  1. Dissolve 0.3% LA gellan gum in deionized water, heat to ≥90℃, and maintain for 5 minutes.

  2. Cool to 80℃, then slowly add the corresponding concentration of calcium solution with gentle stirring for 1 minute.

  3. Immediately pour into molds and cool to set at room temperature (25℃, 50% relative humidity).

II. Mechanism of Calcium Ion Concentration on Gel Transparency and Color

Low-acyl gellan gum forms a gel network through calcium ions (Ca²⁺) in an "egg-box" structure. As Ca²⁺ concentration gradually increases:

1. Structural densification: Ca²⁺ forms cross-linking bonds between gellan gum double helices. As concentration increases, the network becomes denser, leading to enhanced light scattering.

2. Phase separation tendency: When Ca²⁺ concentration is too high (>0.10%), excessive local cross-linking induces microscopic phase separation, forming micro-regions with sizes close to the wavelength of visible light (400–700 nm), significantly enhancing light scattering and resulting in a milky white appearance.

3. Transparency variation pattern:

   • Ca²⁺ ≤ 0.08%: Gel is transparent or slightly opalescent (transparency > 85%, measured as transmittance at 600 nm).

   • Ca²⁺ = 0.10%: Clearly milky white (transparency approximately 60–70%).

   • Ca²⁺ ≥ 0.15%: Significantly white, opaque (transparency < 40%).

III. Mechanism of Calcium Ion Concentration on Gel Strength

Gel strength (Bloom strength, g/cm²) depends on Ca²⁺ cross-linking density and network uniformity.

• Optimal cross-linking range (0.06–0.08%): Ca²⁺ uniformly cross-links, forming a continuous, dense, and homogeneous three-dimensional network, achieving peak strength.

• Excessive cross-linking range (>0.10%): Localized over-cross-linking leads to network heterogeneity, creating stress concentration points, making the gel brittle and reducing macroscopic strength.

IV. Quantitative Effect of Calcium Concentration on Gel Color and Strength

*Note: Transmittance is measured with deionized water as 100% reference; gel strength is measured using a TA.XT texture analyzer with a cylindrical probe (10 mm diameter), 50% compression ratio, and speed of 1 mm/s. Data are average values of three replicates.

V. Application Recommendations

• High-transparency gel products (e.g., jelly, transparent gummies): Recommended Ca²⁺ concentration: 0.06–0.08%