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| Back extrusion test for assessment of consistency |
There is now diversity and new opportunities in formulating “table sauces”, both sweet and savoury, with a wide variety of flavours, rheological and textural properties which can be obtained or modified using different types and concentration of ingredients.
By controlling formulation and processing, a wide range of physical properties can be produced. In describing the consistency of foods, terms like “mouthfeel”, “body” and “stringiness” can all be understood and require a method for measurement.
Measuring Consistency and Cohesiveness
The Back Extrusion Rig from Stable Micro Systems offers an invaluable measure of product consistency.
A sample container of the test matter is compressed by a disc plunger attached to the TA.XTplus texture analyser, which extrudes the product up and around the edge of the disc. The effort taken to do this is measured using Exponent software and results give an indication of consistency. Such a measure relates to the body or flowing nature of the product, its mouth coating potential and spoonability. Achieving the desired texture of semi-solid product is therefore possible, and can be monitored from batch to batch, and throughout the product’s lifespan.
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Texture analysis can help manufacturers achieve full fat standards of texture in low fat products, which consumers would prefer. By taking objective measurements of the differences between products, manufacturers can adjust formulation to give a texture equivalent to the full fat version in the low fat product.
The right-hand graph above shows the results of two back extrusion tests on full fat and low fat mayonnaise using the TA.XTplus Texture Analyser. The curves generated by this test and displayed in Exponent software demonstrate that the low fat mayonnaise sample is thicker and more of a gelled texture compared to that of the smooth flowing consistency of the full fat sample.
This is shown by the higher initial force on the low fat sample curve, the jagged force profile and the total area under both the positive and negative regions of the curves. Such is typical of low fat products where most often this "gelled” texture is introduced by the addition of starches to compensate for the loss of mouthfeel when fat is absent or reduced.
One reason that this extrusion technique is popular, compared to forward extrusion, is that you need not perform this test in the containers which are provided by Stable Micro Systems. In many situations it may be disadvantageous to decant your sample from one container into the provided back extrusion containers due to disruption of the sample structure, since breakage of any gel structure during decanting is almost inevitable.
In this case, using the same procedure and extrusion discs, you may choose to test your sample in the container in which it was originally deposited or formed. This is certainly acceptable so long as you always test within the same size container, in order to make a legitimate comparison.
Analysing the texture of unsupported structures such as these is also important to provide manufacturers with vital information as to a product’s consistency throughout its shelf life.
Request our article The Thick (and Thin) of it which looks at the texture analysis of semisolid products.
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!
To discuss your specific test requirements, click here...
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