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.

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.

Six recent interesting articles about Texture Analysis

Texture is a food product’s defining factor – getting it wrong can mean rejection by consumers. A product could taste great, have a healthy advantage, and look fantastic, but if the texture doesn’t hit the mark, it just won’t work. 

For those who are new to this field of science, the following recent articles give a good introduction in several explanatory styles and highlight the importance of food texture:

Altering Data Acquisition Rate and Corner Frequency to Optimise your Texture Analysis

DATA ACQUISITION RATE 

Otherwise known as sampling frequency, the data acquisition rate of a test is defined by the number of data points collected per second (pps). In general, a higher data acquisition rate allows the collection of more detail during a test. The maximum possible data acquisition rate has increased over the years with improved technology and increased computer memory.

The recently released Connect range of Texture Analysers allows data collection up to 2000pps. This higher acquisition rate (2000pps) detects up to four times as many force changes per second as the previously available rate (500pps) and so it is very well-suited to applications involving high rate fracture, such as crispiness or high speed events such as in the measurement of adhesives or brittle samples. 

How to operate a Texture Analyser using a range of devices

Whether you are new to texture analysis, are an experienced super user, or have specific requirements, you now have the flexibility to choose how you interact with a Connect Texture Analyser.  

We offer three ways to run your instrument. Each can be used independently from each other, or you can have a combination of all three. Whichever suits your requirements, the choice is yours.

How to operate your Texture Analyser

Touchscreen

The Touchscreen is supplied with all of our Connect Texture Analysers and is capable of controlling your instrument and running simple tests. It is ideal for providing a quick result with some single point analysis, such as Maximum Forces in both compression and tension tests.

How to Measure Whole Fruit Volume

Quality components of fruits and vegetables are classified into the external such as size (weight, volume and dimensions), colour, shape (diameter/depth ratio), external defects etc. and the internal such as sugar content, acid content, firmness, maturity etc and internal characteristics.

Agricultural products have the characteristics of being ‘low value added’ as compared with other industrial commodities. Because of this, application of start-of-the-art technology to agricultural sectors has been relatively recently activated and various up to date techniques have now reached the point of practical implementation.

Plasticity Measurement of Soft Solid Foods

Plasticity is a property shown by many materials, such as polymers, metals and the majority of foods. It is the ability of a material to undergo permanent deformation. 

If you press your finger on a spring, it returns to its original shape. If you made that spring out of cheese, it would not spring back as far – it would remain squashed. When stretching a sample, plasticity is seen on the force-distance graph as a change in gradient after the initial linear section (straight line). The point where the gradient changes is known as the ‘yield force’. If this point is reached and more force is applied, the sample will be permanently changed. Before this point, the behaviour is elastic and spring-like.

Testing Products with a Crust, Skin or Multilayers

Products with a crust, skin or multilayers bring textural variety to a product. The breaking of the skin of an apple when bitten into or the biting through the layers of the perfect pastry product brings a textural sensation that is highly desirable and anticipated. Failure to notice a difference in the layers of such products brings disappointment.

The collection of detail of a thin, brittle, laminated or multi-phased structure is best performed with a small diameter probe or thin, sharp fixture. A larger probe such as a platen, cylinder or sphere will give bulk compressive properties but will not resolve the properties of each layer. It is beneficial to penetrate the sample slowly in most cases to give a larger time gap between fracture or puncture events so they can be more easily identified.

Implications of spreadability for dairy and bakery products

The spreadability of margarine and butter is of paramount importance for consumer acceptability. It is a physical property and results from the fact that these products consist of a dispersion of solid fat crystals in liquid oil.

The ratio of solid to liquid fat in a product is probably the most important factor determining hardness and spreadability. However, hardness and softness are not the only factors influencing spreadability; smoothness and brittleness are also important. 

Temperature-Controlled Texture Analysis of Fats and Oils

Fats and oils perform a key role in defining the sensory characteristics of our favourite prepared foods. They affect the structure, stability, flavour, shelf-life, palatability, mouthfeel and visual appearance of food products.

For manufacturers to obtain the desired performance, it is important to recognise that different applications require a fat or oil product with different physical and organoleptic properties. 

Toast your Roast with Texture Analysis

Variations on ‘Roast Dinner’ are eaten for different occasions all over the world – a roast joint of meat, potatoes, vegetables and gravy, often followed by a stodgy pudding such as an apple pie.

This is a meal that consumers look forward to so it is important that the texture of each component is no less than perfect. This analysis would be carried out for the purpose of calculating ideal cooking times, in the case of a supermarket or a chain restaurant, or to test the quality of supplied ingredients.

Texture Analysis – Time for Tea!

Texture Analysers are made in the South of England, where afternoon tea stacked high on a triple tiered cake stand is a staple for any big celebration.  

Our customers around the world may be surprised to find some items here that aren’t so different from their own national food.

The first component of afternoon tea is a large, fluffy scone, cut in half and spread with sticky jam and clotted cream. There are regional arguments for whether jam or cream should be applied first, but in both cases cream and jam that are hard and difficult to spread cause the scone to break up under the knife, which is very undesirable. The softness of the inside of a scone can be assessed by preparing a cubic sample, having cut the crusts off, and performing a compression test with a large cylinder probe. A soft sample will yield under a low force.

The Perfect Texture of Lunch

A sandwich, a bag of crisps and a can of soda – the lunch eaten by millions of people around the world every day.

They are not aware of the meticulous testing that has gone into every stage of their meal, from the packaging down to the wheat flour used to make their bread. It is no surprise that food manufacturers focus so much of their effort into tailoring these items so they are a perfect compromise between cost and quality, to be pleasing to the customer but not expensive to manufacture.

Texture Analysis of your Breakfast

A satisfying breakfast sets you up for the rest of the day. It is often composed of many different components, each with a different texture, and there are many variations around the world.

An example of a widely-consumed breakfast is the “continental breakfast”, comprising of bread, cold meat, cheese, yoghurt, fruit and cereal. Regarding texture, bread should be resilient (brittleness in bread suggests staleness), ham and salami should be tender, and breakfast cheese may be soft.