How to measure gel strength

Gel Strength refers to the ability of a gel to form and retain a gel structure and resist deformation under stress. It is a measure of the firmness or structural integrity of a gel and is often tested to assess its mechanical stability and performance. In various industries, including food, pharmaceuticals, and cosmetics, gel strength is critical for ensuring the desired texture, functionality, and quality of products such as gelatine desserts, pharmaceutical capsules, or cosmetic gels. The properties of gels, including elasticity and rupture force, are essential for products such as coronary stents, wound dressings, and soft gel capsules, as well as cosmetics like creams and pastilles.

In the gelatine industry, gel strength is commonly measured as Bloom, which represents the force (in grams) needed to depress the surface of a gelatine gel by 4mm using a standard 0.5" ⌀ Cylinder Probe.

Gel strength measurement using a Texture Analyser is vital for assessing the mechanical properties of gels across various industries, including food processing, pharmaceuticals, and cosmetics. Below are key applications:

• Jelly and gelatine firmness testing: The gel strength of a gelatine dessert determines its firmness and mouthfeel. A higher gel strengthproduces a firmer, more solid dessert, while a lower gel strength results in a softer, more wobbly texture. The gel strength in pectin-based jellies or jams affects the spreadability and structural integrity of the product. Stronger gels maintain their shape better, while weaker gels spread more easily. Gel strength is crucial in the production of gummy candies, where a balance between chewiness and firmness is required. Stronger gels provide a more substantial chew, while weaker gels result in softer, more delicate candies.
• Pharmaceutical gel/cream consistency analysis: Assessing the gel strength and consistency of pharmaceutical topical gels by measuring the force required to deform the gel. The gel strength of topical treatments like ointments or medical gels affects their ability to hold their shape and stay on the skin. Gels with lower strength may spread more easily, while stronger gels may stay in place longer.
• Cosmetic gel texture testing: The strength of hair gels affects their ability to hold hair in place. High-strength gels provide firmer hold, while low-strength gels allow for more flexible styling. Gel strength in skin care products can influence how the product spreads on the skin and its ability to stay in place without running or dripping.
• Food emulsion gel analysis: Testing the gel strength of emulsions and thickened food products, like sauces, by measuring the force needed to deform them.
• Dental gel strength evaluation: Measuring the gel strength of dental impression materials and adhesives by evaluating the force required to penetrate or deform the gel.
• Pharmaceutical capsule gel strength testing: Assessing the gel strength of soft gel pharmaceutical capsules by measuring the force required to rupture them and release their contents. The strength of gel capsules is important for maintaining the integrity of the medication during storage and consumption. Capsules with higher gel strength are more resistant to breaking or leaking.
• Hydrogel strength analysis: Evaluating the mechanical properties of hydrogels used in medical applications, such as wound dressings, by measuring the force needed to compress or deform them.
• Agar gel strength measurement: Testing the gel strength of agar gels used in microbiological applications by measuring the force required to puncture them.
• Biopolymer gel strength analysis: Evaluating the gel strength of biopolymer gels used in tissue engineering by measuring the force required to deform the gel scaffold.

In these examples, a Texture Analyser applies controlled forces/distances to measure gel strength, ensuring product quality, consistency, and performance across industries like food, pharmaceuticals, and cosmetics.

In a typical gel strength test, a cylindrical probe is used to penetrate the gel at a constant speed. The gel strength is typically reported as the peak force required to depress the gel by a specific distance.

1/2" Ø Cylinder Probe with radius

Cylinder Probes

A full explanation of these curves and their analysis can be accessed within Exponent Connect software. Existing Exponent users can upgrade to Exponent Connect specification.

Below is a video example of how we can help you understand curve analysis for an example property. 

• Temperature: Temperature significantly influences gel strength measurements, as it can affect the molecular structure and interactions within the gel, potentially altering its mechanical properties. Gels are typically stronger at lower temperatures, as the molecular structure is more rigid and stable. Higher temperatures can cause gels to soften and lose strength, leading to lower peak forces on the graph and easier deformation.
• Sample preparation: Consistent and precise sample preparation methods are crucial for reproducible gel strength measurements, as variations in mixing, heating, or cooling processes can lead to differences in gel formation.
• Probe geometry: Different diameter cylinder probes may be used depending on the gel type and application. Radiused and non-radiused perimeters are also available depending upon the requirement of the standard method.  Radiused probes avoid the ‘cutting’ of the sample around the probe perimeter at small deformations.
• Resting time: The duration allowed for the gel to set or stabilize before testing can affect its strength, as some gels continue to develop structure over time.
• Type of gelling agent: Different gelling agents result in different gel strengths. For example, gelatine typically produces softer, more elastic gels, while agar and pectin can form stronger, more rigid gels.

The Stable Micro Systems Texture Analyser stands out in optimising gel strength measurements through its comprehensive approach and specialised features. Equipped with industry standard cylinder probes for GMIA and ISO methods, it precisely quantifies multiple gel properties including bloom strength, rupture force, and elasticity in a single test and is officially recommended by key industry associations.

The Texture Analyser’s high precision, with force resolution of 0.1g and distance resolution of 0.001mm, ensures accurate results. Exponent Connect software captures detailed force-time-distance profiles for in-depth analysis, while Stable Micro Systems' expertise in method development and data interpretation, makes it the ideal choice for industries seeking to refine product formulations and maintain quality standards in gel strength testing.