General Testing Methods
Principles of texture analysis and physical property testing
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 behavior and, in many cases, imitating human interaction with a sample in real life.
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Puncture and PenetrationEvaluates resistance to penetration of usually a small probe compared to the sample size or samples that must be contained as they are non-self supporting. Typical Samples: Solid, semi-solids, foams and packaging Common Probes: Flat or cylindrical probes, compression platens, Ottawa Cell |
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CompressionMeasures firmness, hardness, and deformability when a sample is compressed, more often in its entirety. Typical Samples: Gels, coatings, fruits, soft solids Common Probes: Small-diameter cylinder, cone, needle or ball probe |
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Cutting and ShearingDetermines toughness and bite characteristics by slicing or shearing through a sample. Typical Samples: Meat, gels, vegetables, packaging films Common Probes: Blade set, Warner–Bratzler shear, craft knife rig |
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ExtrusionAnalyses flow properties and consistency of viscous or semi-solid materials during forced displacement. Typical Samples: Pastes, gels, semi-liquids Common Probes: Back Extrusion Rig, Forward Extrusion Rig, Spreadability Rig |
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Bend and FlexureAssesses flexibility, brittleness, and fracture behaviour in rigid or semi-rigid samples. Typical Samples: Biscuits, bars, plastics, laminates Common Probes: Three-point Bend Rig, Lipstick Cantilever Rig |
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TensionMeasures tensile strength and extensibility when a sample is stretched. Typical Samples: Films, adhesives, textiles, plastics Common Probes: Tensile Grips |
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AdhesionQuantifies stickiness, tack, and peel strength when separating surfaces. Typical Samples: Creams, gels, adhesives Common Probes: Peel Rigs, Spherical Probe |
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FrictionMeasures the force to move one material over another. Abrasion and combability are also physical property measurements that can be performed that fall within frictional testing. Typical Samples: Packaging materials, shaving gels, and cosmetic products Common Probes: Horizontal Friction System |
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Other Test TypesA range of novel imitative testing solutions for unusual properties. Typical Samples: Coatings, combing, hair suppleness, ice cream and abrasion products Common Probes: Variety of unique rigs |
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.
Understanding imitative, empirical and fundamental testing
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
| Testing Type | Purpose / Result Type | Advantages | Limitations / Typical Applications | |||
| Imitative | Mimics real-world handling or use; descriptive results (e.g. bite force, spreadability) | Realistic, consumer-relevant | Test-specific, not standardised; used in food, cosmetics, packaging | |||
| Empirical | Measures response under controlled conditions; relative results (e.g. firmness, adhesiveness) | Reproducible, QC-friendly | Geometry-dependent; used for quality control and benchmarking | |||
| Fundamental | Determines intrinsic material properties; absolute results (e.g. modulus, yield stress) | Scientifically precise | Complex setup and analysis; used in R&D, formulation, material science. Requires precise sample preparation and accurate dimensional control which may not be possible. |
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.
