Why change from the Standard Method approach?

Tape Unwinding Rig A/TUR

A Standard Test Method is a definitive procedure that produces a test result. In order to ensure accurate and relevant test results, a standard test method is explicit, unambiguous, and experimentally feasible, as well as effective and reproducible.

A standard test method can be considered an experiment that determines one or more characteristics of a given sample and the detail of the test method is usually as a result of creation from a number of experts in that measurement field. Within the materials testing industry, for example, there are an enormous number of standard methods (e.g. ASTM, ISO) that have been developed to measure specific sample characteristics. 

Typical examples of those that use Texture Analysers or Materials Testing equipment are:

• ASTM D882-02: Tensile test of thin plastic sheeting (thickness<1mm)
• EN 1944:1996 - Self Adhesive Tapes - Measurement of Unwind Adhesion at Low Speed

When reporting results in an academic paper or industrial report these standard methods will have been adhered to for the collection of the results and are more globally understood by others using the same standard methods. It is for this reason that standard methods have their place in the laboratory.

In the food industry, for example, there are far fewer standard methods for physical property measurement. However, you may already be following one of few specific Standard methods to test your samples, e.g. ISO Gelatine Bloom Strength, AACC Bread Freshness, AACC Pasta Firmness, ASTM Petroleum Wax Firmness, ASTM Adhesive Peel Strength.  

The limitations of applying standards, however, is that their biggest advantage (of being specific) can be a major disadvantage (or restriction) to the measurement. All too often, operators are forced to use a standard method to measure a property of their product when:

• The property that the standard method measures is not the most important, or interesting, measurement that could be performed on the sample, or
• The sample preparation procedure may be difficult (or impossible) to conform with given the sample to be tested is different to the sample for which the test method was developed.

A well-written test method is important. However, even more important is choosing a method of measuring the correct property or characteristic. Not all tests and measurements are equally useful: usually a test result is used to predict or imply suitability for a certain purpose. However, it would seem more important to measure the most important characteristics of a product than to follow a seemingly pointless standard method that does not ideally characterise the product. 

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 is called an ‘Imitative Test’. This type of test usually also makes data interpretation easier for you to understand.

For certain industries consensus regarding the method of measuring the physical characteristics of products is virtually impossible and whilst procedures can be agreed upon internationally, they are not always universally accepted. Standardisation of methods is essential if investigations carried out by different groups are to be directly comparable.

The methods used for physical testing should measure the desired characteristics necessary to monitor the process, but need not always be comparable with other laboratories, where different criteria may be important. Where international comparison is important it is essential that methodologies be standardised. This would include all aspects of the testing procedure and this is an area of which the reference methods are primarily directed.

In contrast, where direct measurements are being made of the physical properties of a product, the experimental methodologies should not be constrained by reference methods. Instead researchers are encouraged to develop and use methodologies that enhance the precision and accuracy of testing methods and lead to an understanding of the basic mechanisms. It is likely that new understanding will lead eventually to methods that more closely predict consumer assessment of product characteristics. The Stable Micro Systems range of Texture Analysers provide the flexibility of testing principles (e.g. compression, penetration, tension, extrusion, etc.) and the endless option of probes, fixtures and data analysis techniques within the software for texture analysis and fully customisable test settings.

Whilst standard methods are particularly useful for traditional material forms that have not changed over the decades and are fully accepted there lies another world where creativity has taken off into new materials and material forms for which these standard methods cannot be applied. One example of such an issue is in the field of pharmaceutical development. Traditional methods are well established for the testing of tablets, gels, suppositories, medicated liquids that are manufactured in their traditional form, however, innovative dosage forms have been developed such as disintegrating films, capsules, chewable pastilles for which there is no standard method to apply for the measurement of their physical (or textural) characteristics. Alternative testing methods that accommodate the testing of samples of varying types and dimensions and the range of additional material characteristics which can be measured, are required.

Not only are new non-standard methods viable where sample dimensions cannot be prepared according to the standard but also where the operator may wish to modify the test parameters (such as the test speed) to more closely mimic the situation under which the sample is to be typically used.

It must be noted, that it is always of utmost importance to recognise that the changing of a test parameter or sample preparation technique should be reported for the purpose of comparison later.

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For more information on how to measure texture, please visit the Texture Analysis Properties section on our website.

The TA.XTplus texture analyser is part of a family of texture analysis instruments and equipment from Stable Micro Systems. An extensive portfolio of specialist attachments is available to measure and analyse the textural properties of a huge range of food products. Our technical experts can also custom design instrument fixtures according to individual specifications.

No-one understands texture analysis like we do!

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