Test types

Texture analysis is the science of measuring the physical properties of materials – how they deform, flow, or break under applied forces. Using a Texture Analyser, these properties can be quantified objectively to assess product performance, quality, and consistency across a wide range of industries, from food and cosmetics to pharmaceuticals, packaging, and adhesives.

A Texture Analyser operates by applying controlled forces/distances to a sample and recording its response. Depending on the test type and the probe/attachment used, it can replicate compression, penetration, cutting, extrusion, stretching, bending, or adhesive interactions, giving valuable insights into the material’s mechanical behaviour and in many cases imitating human interaction with a sample in real life.

Each of these test types provides unique insights into product texture and performance, helping manufacturers ensure their products behave as intended during manufacture, storage, and end use.

Our range of instruments can carry out fundamental, empirical and imitative tests, covering those relating to texture analysis, materials science and rheology of solid, semi-solid, viscous liquid, powder and granulate materials.

For each method, fixture geometry and test speed significantly affect results. Use your Texture Analyser’s application study library in the Education Zone within Exponent Connect software to find validated test protocols for your material type.

Texture analysis can be approached in several ways, depending on the level of detail required and the purpose of the measurement. Tests performed on a Texture Analyser are generally described as imitative, empirical or fundamental, each providing different but complementary information about a material’s behaviour under force.

Imitative testing

If you’re not bound by any existing constraints and are looking for the most simple testing solution, sometimes the easiest approach is to set up a test that closely imitates the way the product is evaluated in real life. This type of test usually also makes data interpretation easier for you to understand. Imitative tests replicate or mimic real-world actions such as biting, spreading, cutting or peeling, allowing objective measurement of how a product performs in use and closely reflects consumer perception and handling. However, test results are specific to the test design and may not be transferable.

Empirical testing

Texture Analysers are very often used for quality control of irregular products by the use of empirical measurements. The force required to crush a tablet or the distance a biscuit bends before it snaps are invaluable pieces of information to manufacturers looking to develop new products or ensuring products perform correctly during spot checks. This type of test is ideal for products that have an unusual geometry, but it is also useful for testing more complicated systems, such as the combination of a product and its packaging (a box of eggs, the force to open a ring pull can or a yoghurt in its pot) with the added benefit of time saved by allowing a product to be tested straight off the supply line which is ideal for quality control.

Empirical tests measure a sample’s response to a defined deformation or force under controlled conditions. Results are typically expressed in relative terms, such as firmness, consistency or adhesiveness. This test type is dependent on probe geometry and test conditions and does not produce absolute material property values but results correlate well with sensory data and manufacturing parameters.

Fundamental testing

A large number of users use their Texture Analyser to calculate fundamental parameters by taking into account the geometry and dimensions of the sample as well as the specifics of the test set up along with the relevant engineering equations. This type of testing allows easier comparison of different samples and comparison with literature data, but does generally require specific sample preparation (which is sometimes not possible with novel samples) and more sophisticated analysis to convert forces to stress and distances to strain is usually needed.

One of the most commonly used fundamental tests is the measurement of Young’s Modulus. Fundamental tests generally assume (1) small strains (1-3% maximum); (2) the material is continuous, isotropic (exhibiting the same physical properties in every direction), and homogeneous; and (3) the test piece is of uniform and regular shape. Whilst fundamental tests are popular in the materials testing world most textural tests made on foods fail to comply with the three assumptions listed above. Fundamental tests are not used to any great extent in the food industry as they do not correlate as well with sensory evaluation as do empirical tests but they do have a place in some research laboratories. Szczesniak (1963) aptly described the usefulness of fundamental tests as follows:

Since most foodstuffs do not have simple rheological properties that are independent of stress and strain conditions, and since rheological properties once measured and defined are not meaningful in a practical sense unless related to functional properties, fundamental tests serve the greatest value to the food technologist by providing bases for the development of more meaningful empirical tests.

A wide number of fundamental calculations and analysis are built into Exponent Connect for a wide range of test types.

Comparison overview

Texture Analysers provide the operators with ultimate control and test flexibility for measuring all types of physical/textural properties of solid and semi-solid systems by their ability to accommodate a wide range of probes and attachments (devices to test food structure) that can be attached to the Texture Analyser base and/or arm to perform a wide range of test types.