Puncture and penetration testing

A penetration or puncture test is a method used to evaluate the resistance of a material when a probe is driven into it. During the test, the Texture Analyser records the relationship between force and displacement over time, producing an objective measure of properties such as hardness, gel strength, toughness, or actuation force. Because the probe physically ruptures or deforms the sample, penetration tests are considered destructive and irreversible. They also rely on the assumption that the sample area is larger than the probe’s contact area. In some cases, particularly when dealing with very hard products, penetration testing may be the only feasible option if the instrument’s force capacity is limited.

To carry out a puncture or penetration test, the Texture Analyser positions a probe above the sample and drives it downward at a controlled speed. As the probe enters the material, the instrument continuously records the force applied relative to the distance travelled or the time elapsed. Once the probe reaches a specified depth or the sample ruptures, the Texture Analyser identifies the maximum force or the force at that depth. These values are then translated into meaningful performance indicators, such as hardness, gel strength, toughness, or actuation force, providing researchers and product developers with precise data about the material’s behaviour under stress.

Puncture and penetration tests are commonly used to quantify firmness, gel strength, dipping consistency, product toughness, fracture force, cake breaking strength, semi-solid consistency, and actuation force.

Single or multiple parameters such as peak force, penetration depth, work to penetrate and slope/modulus can be collected from the graph. These parameters help characterise how easily a material yields or fractures under applied force, making this test ideal for products such as gels, creams, tablets, films, and food samples.

To learn more about how these properties are measured, visit our Textural properties page.

Probe types

• Cylindrical probes (typically 2-10 mm diameter) – general-purpose; small diameters for rupture/skin testing and more detailed measurement of multiple structures within a sample.
• Conical probes – used to assess the firmness, consistency, and flow behaviour of soft or semi-solid materials such as gels, creams, pastes, and is often chosen to replace tests previously performed on a penetrometer for the testing of waxes and spreads. Its tapered design allows for gradual penetration, meaning the contact area increases smoothly with depth which can make data interpretation more difficult.
• Needle probes – for fruit flesh/skins and fine measurement of multiple structures within a sample.
• Spherical / hemispherical probes – where surface curvature or imitation of a finger is needed (actuation).

Multiple-penetration rigs

Use multiple-probe rigs where product variability is high (fruits, mixed matrices) to increase repeatability; they allow simultaneous multiple sampling across a single sample.

Materials and bespoke probes

Standard probes come in Delrin, stainless steel or aluminium. Bespoke geometries or materials can be produced to customer specification for specialised tests.

• Penetration: Use when you need to rupture a sample to mimic it being punctured by a small item, or the sample is thin, non-self-supporting, has a skin/crust or you must mimic a probe/actuation. Penetration is a suitable test choice when samples cannot be prepared to the same dimensions as the use of a probe smaller than the sample provides a consistent contact area. A penetration test is also a way of reducing the force measured when a higher Load Cell is not available for testing, by way of its reduced probe/sample contact area. Typical examples: apple firmness, Bloom gel strength, packaging puncture, cosmetic wax firmness.
• Compression: Use when measuring bulk deformation without penetration (e.g. whole biscuits compressed between platens) or a number of test pieces to overcome between piece variability. If the sample area ≤ probe contact area, compression principles apply. When choosing to perform a compression test of a single piece the sample dimensions must be carefully controlled to avoid the production of variability by changing sample size.

• Bloom test – according to ISO, BS and GMIA standard methods using a 0.5” cylinder probe.
• Bakery products – there are a number of AIB standard methods that use penetration tests to measure various firmness/staleness properties of e.g. bagels, cake.
• Lipstick and waxes – ASTM Standard method D 1321-95 and ASTM Standard method D937-92 for the measurement of hardness using a 2mm needle probe and conical probe, respectively.
• Pharmaceutical – a few of the ISO standard methods for syringe testing use the principle of penetration testing.
• There are several ASTM, BS and ISO methods for the puncture resistance measurement of paperboard, films and packaging materials.