Novel Physical Testing Methods using the Texture Analyser

Our probes and fixtures range has developed due to the need for new ways to hold/support and test samples in ways that haven’t been previously available for traditional texture analysis test methods. For example, instead of using the Texture Analyser in an up and down mode you could support the instrument on its side and measure friction in a horizontal plane. This could be for the measurement of frictional properties of packaging or to assess the grating potential of cheese.

Adhesion Testing for Texture Analysis & Materials Testing

What is an adhesion test?

Adhesion is the force that resists the separation of two bodies in contact. An adhesion test measures the adhesive characteristics of a product by measuring the forces to separate the product from the test surface which it comes into contact with. Adhesiveness ('Stickiness') is most commonly measured with a cylinder probe, which is pressed (application of compression), onto the surface of the sample after which the force to pull the probe off it is measured. The higher the force to separate these surfaces, the more adhesive is the product. The distance the probe needs to be pulled away from the product before the two surfaces are separated will also indicate its viscoelastic behaviour, and depending upon the product, its ‘tailing’ or ‘stringiness’ characteristic.

Cutting/Shearing Testing for Texture Analysis and Materials Testing

What is a cutting/shearing test?

In general, any texture analysis test that involves the use of a type of blade to perform the test, is performing a cutting or shearing action on the sample. A number of empirical fixtures feature a single blade or a number of blades which cut/shear through the sample, under specified conditions. The maximum force required and/or the work necessary to achieve this (i.e. the area under the curve) is taken as an index of firmness, toughness or fibrousness of the sample. Whilst empirical or imitative, shearing tests are very popular, particularly for the assessment of food texture and in particular the measurement of ‘bite force’.

Fracture/Bending Testing for Texture Analysis and Materials Testing

What is a fracture/bending test?

This type of test can measure the fracture and break strength of hard and brittle products (or their flexibility) by bending the sample, usually until a break occurs. If a break does not occur whilst the sample is flexed then a measure of its flexibility can be performed instead – a degree of flexibility can be desirable or a characteristic to be avoided, depending upon the sample. Stable Micro Systems enables a wide range of tests in this field, using fixtures such as the Three Point Bend Rig which are adaptable to many types of sample, and also specialist attachments like the Crisp Fracture Support Rig or the Spaghetti Flexure Rig.

Use of by-products for agricultural benefit

Crop protection, including weed management, is a critical issue in agriculture. Mulching, which consists of covering the soil surface with organic or inorganic materials, is used to control soil moisture, soil temperature, nutrient loss, salinity, erosion, soil structure, etc. Its benefits for the growth and yield of annual and perennial crops have long been recognised. Although it is an age-old practice for managing weeds, mulching has largely dwindled since the widespread use of herbicides; however, now it is gaining importance in the context of sustainable agriculture. Different mulching materials have been used in different crops in different climatic environments for weed management, and results vary according to the chosen approach, growing practices, conditions and species. These materials include crop residues, non-degradable plastic films, and also biodegradable films. The lifetime of an agricultural mulch varies considerably (i.e., months to years) depending on the nature of the material, its application, its thickness, and the environmental conditions.

Extrusion Testing for Texture Analysis and Materials Testing

What is an extrusion test?

There are generally two types of extrusion test in texture analysis: backward (or back) and forward. Of the various extrusion techniques the one favoured in recent years is back extrusion. The sample is contained in a strong cell with a solid base and an open top. A rod with a disc is then forced down into the container until the food flows up (backwards) through the space between the disc and the container walls which is called the annulus.

Tensile Testing for Texture Analysis and Materials Testing

What is a tensile test?

A tensile test pulls or stretches a sample and as a result the extensibility/elongation and tensile strength properties are measured in terms of force required to stretch and distance something can be stretched to.

The ultimate tensile strength of a material is defined as the maximum attainable load, acting on a specimen in a tensile test, divided by the original cross-sectional area of the specimen.

A conventional tensile test assumes that the sample fractures almost instantaneously in a plane that is approximately perpendicular to the plane of the applied tension. The maximum force is the tensile strength of the material.

Compression Testing for Texture Analysis and Materials Testing

What is a compression test?

A compression test is perhaps the most simple and popular test of instrumental texture measurement. In its simplest method, a sample is placed on a flat base/surface and a flat probe/platen is lowered onto the sample to a given force or distance (or the sample is compressed to a percentage of its original height). The sample is deformed and the extent of the deformation and/or the resistance offered by the sample is recorded. Simple compression tests are often termed uniaxial compression which means that the sample is compressed in one direction and is unrestrained in the other two. Either a low or high degree of compression can be chosen but a high degree of compression will usually cause the product to rupture, spread, fracture, or break into pieces.

Puncture and Penetration Testing for Texture Analysis and Materials Testing

What is a puncture/penetration test?

In a penetration/puncture test a probe is made to penetrate into the test sample and the force necessary to achieve a certain penetration depth or the depth of penetration in a specified time, under defined conditions, is measured and used as an index of e.g. hardness, firmness, toughness.

Both test principles cause an irreversible change in the sample and assume that the sample being investigated is of larger area than the contact area of the probe in use; a sample smaller than the probe contact area would assume compression principles.