How to measure swelling/proving

Swelling refers to the increase in size or volume of a material when exposed to a liquid, solvent, or moisture. It is an essential property in various applications such as pharmaceutical tablets, gels, films, sponges, and food products. For yeasted doughs this property would be part of the ‘proving’ stage as the dough absorbs water or expands due to gas production. Swelling can be measured by tracking changes in force or distance using a Texture Analyser, which can compress a product slightly and maintain a small force on the product while monitoring changes in height or volume as swelling occurs. Understanding the swelling behaviour of materials is crucial for optimising product formulation, shelf life, and performance in industries like pharmaceuticals, food, and materials science.

Swelling measurements using a Texture Analyser help quantify the expansion or dimensional changes in materials when exposed to specific liquids or environments. Below are key applications:

• Pharmaceutical tablet swelling analysis: Evaluating the increase in size or thickness of pharmaceutical tablets when immersed in gastric fluids to assess their swelling behaviour over time.
• Dough proving measurement: Measuring the volume or increase of yeasted dough to evaluate their proving rate and end point.
• Hydrogel swelling measurement: Assessing the swelling of hydrogel materials used in drug delivery by measuring the increase in volume when immersed in a liquid.
• Polymer film swelling analysis: Testing the swelling behaviour of polymer films by measuring their expansion when exposed to solvents or chemicals.
• Cosmetic product swelling evaluation: Evaluating the volume increase of gel-based cosmetics when exposed to water or applied to wet substrates to assess their swelling properties.
• Polymer bead swelling analysis: Measuring the size increase of polymer beads used in chromatography as they swell when exposed to specific solutions.
• Edible film and coating swelling measurement: Assessing the swelling behaviour of edible films or coatings when they come into contact with food or moisture.

In these examples, a Texture Analyser is used to monitor the expansion of materials, providing critical data for product development, quality control, and material performance analysis. These swelling measurements are key to ensuring the reliability and functionality of products across various industries.

In a typical swelling/proving test either repeated penetration tests to the same force can produce a force vs. distance curve where repeated penetration shows a change in distance with each penetration as the sample swells.  Alternatively, a probe larger than the sample can be held at a low force over the sample and the distance monitored during swelling/proving.

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Two main techniques are used to measure swelling and proving:

Repeated compression/penetration test

When measuring swelling in this way, the force vs distance graph typically shows an increase in distance value to achieve the same force. From the graph you can observe/obtain the following:

• Swelling time
• Swelling rate
• Degree of swelling

Compression test holding force

If the force is held on the surface of the sample any increase in volume will require the probe to move upwards to try to achieve the same force.  The distance vs time graph will track this movement. 

A full explanation of this curve and its 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 proving/swelling measurements, as it affects yeast activity and gas production rates in dough and water absorption for swelling materials, with higher temperatures generally accelerating the proving/swelling process.
• Humidity: The humidity level in the proving/swelling environment impacts moisture retention in dough or swelling behaviour for other materials, affecting their expansion.
• Time before testing: The duration of the proving period is crucial, as it determines the extent of fermentation and gas production, directly impacting the final volume and texture of the baked product.
• Probe and vessel geometry: The shape and material of the container in which the sample proves/swells can impact heat distribution and moisture retention.
• Sample size and shape: The dimensions and geometry of the constrained test sample can impact the proving/swelling measurement, affecting the surface area available for liquid absorption or gas expansion.

Dough inflation profile: Using a Dough Inflation System, attached to the Texture Analyser, the pressure and volume necessary to inflate a sheet of dough can be measured.

The Stable Micro Systems Texture Analyser excels in optimising measurements of swelling and proving through its comprehensive approach and versatile features. It accurately quantifies multiple properties including swelling time, rate, and degree, providing a holistic view of a product's swelling characteristics.

The Texture Analyser’s versatility allows for testing a wide range of materials, from tablets and gels to leavened products. It captures detailed force-time-distance profiles, enabling in-depth analysis of swelling behaviour by monitoring changes in height or volume over time. 

The system offers flexible measurement approaches, either by compressing a product and measuring force increases or by maintaining a small force and tracking distance changes using PID control.

Stable Micro Systems' expertise in graphical interpretation and method development further enhances its capabilities making the Texture Analyser the ideal choice for researchers and manufacturers seeking to refine product formulations and maintain quality standards in swelling and proving tests across various industries.