How to measure and analyse the texture of food, cosmetics, pharmaceuticals and adhesives.

Thursday, 4 December 2014

Texture Analysis in action: the Blade Set

Blade and Warner-Bratzler Blade tests on the TA.XTplus Texture AnalyserThe BLADE SET (HDP/BS*) comprises a Warner Bratzler blade, a reversible blade, a slotted blade insert and a blade holder. 

The reversible blade has a knife edge at one end and a flat guillotine edge at the other. In operation, the blade is firmly held by means of the blade holder which screws directly into the Texture Analyser. 

The slotted blade insert is located directly into the Heavy Duty Platform and acts as a guide for the blade whilst providing support for the product.

Measurement of the spreadability of margarine
Cutting force of test on hot dogs using
a Warner-Bratzler blade
 View the Application Video 

Suitable selection of one of Stable Micro Systems' blade/knife options can provide a useful determination of ‘bite force’ of a product.


HDP/WBV: Warner Bratzler Blade Set with ‘V’ slot blade for USDA Standard
HDP/WBR: Warner Bratzler Blade Set with rectangular slot blade

Some more information on this fixture:

Sausage Shearing using Warner-Bratzler
Factors that affect the results of Warner Bratzler shear tests are: uniformity of sample size, direction of muscle fibres, presence of connective tissue and fat deposits, sample temperature, and speed of shearing.

Figure 2 shows typical texture analysis curves comparing a shearing test on two samples of commercially available sausages: one sample is a German frankfurter style sausage (finely comminuted) whilst the other is a Spanish-style pork sausage known as a ‘Chorizo’ (coarsely ground meat product). Both were held at a temperature of 5°C prior to testing in their vacuum-sealed packaging. A few moments before testing, the packaging was removed and the sausages were placed individually under a Warner Bratzler blade in a central position to the triangular inset. This blade was previously attached to a 5kg load cell and positioned carefully within the slotted base insert, taking care to adjust the blade position to avoid frictional effects with the blade guide slot when testing. 

A cutting/shearing test was then performed. This test represents a crude method with little sample preparation which lends itself ideally to quick quality determination. The microstructure of cooked meat emulsion, such as sausage products, may be influenced by the processing conditions, particularly cooking, and its composition, i.e. the type of meat protein, fat-protein ratio, salt level, moisture, degree of comminution and filler content.

The results (as shown in Table 1) indicate that Chorizos required the larger force and total energy (work) to shear. The shearing of muscle fibres and connective tissue requires much larger energy than the breaking of ground or finely comminuted products as is such for frankfurters.

The “Standard” Warner Bratzler Blade

Standard Warner Bratzler shear force involves measurement of cooked meat tenderness using a Warner Bratzler blade (see Figure 3) that adheres to the following specifications: a) shearing blade thickness of 1.016mm; b) a V-shaped cutting blade with a 60 degree angle; c) the cutting edge bevelled to a half-round; d) the corner of the V should be rounded to a quarter-round of a 2.363 mm diameter circle; e) the spacers providing the gap for the cutting blade to slide through should be 1.245mm thick; f) the cooked meat samples should be round cores 1.27 cm in diameter removed parallel to the longitudinal orientation of the muscle fibres; and g) the cores should be sheared once at the centre, perpendicular to the fibres to avoid hardening that occurs toward the surface of the cooked sample (Bratzler, 1932, 1949; AMSA, 1995; Wheeler et al, 1995). 

The maximum force is termed the Warner Bratzler shear force. It is considered that shear tests conducted with modifications to these specifications (e.g. square notch in the blade, square meat samples, straight cutting blade, or blade edge not bevelled) should not be referred to as Warner Bratzler shear force.

The basic concept and design of the Warner Bratzler shear device have however been subject to modification and improvement over the years. Yet, the familiar blade, with its triangular notch in the middle, remains one of the most widely used devices to provide measurements of meat texture quality. 

The width of the blades and the position of the triangle; the speed of the test; the shape, mass, and orientation of the test sample are of course important to interpretation of the results of shear tests but as is always found with “standard” methods and attachments there will always be reasons for modification of the specification of a test fixture and groups of researchers who prefer to move away from a standard to a method that suits their particular research purpose.

One such group is responsible for the development of a new variant of the original Warner-Bratzler blade.

The “European Standard” Warner Bratzler blade
As a spin-off of a workshop on pork quality, held in Helsinki in 1992, a group of scientists with many years of experience in the field of meat quality assessment convened in 1993 for the first time, and subsequently in 1994 and 1995 in Kulmbach at the German Federal Centre for Meat Research to develop internationally accepted reference methods. 

In the Autumn of 1997 these methods (which include the following method for tenderness) were brought into their final form at the Meat Industry Research Institute of New Zealand.
Although Warner Bratzler devices and sample configuration are extremely variable, the recommended equipment according to this “European” network is as follows. The blade should be 1.2mm thick with a rectangular hole 11mm wide and at least 15mm high. The hole should have square smooth edges and the blade should be drawn or be pushed at 50-100mm/min between side plates positioned to provide a minimum gap between blade and plates. The sample should be cut from a block of cooked meat and taken to avoid damage. 

Sample strips should be cut with a 100mm2 (10mm x 10mm) cross-section with the fibre direction parallel to a long dimension of at least 30mm. The sample should be sheared at right angles to the fibre axis. The parameters to be measured from the force deformation curve are the peak force (the maximum recorded) and the total energy. Initial yield may be useful in some instances but will not always be apparent.

*Attachments with code prefix HDP/ must be used in conjunction with HDP/90 Heavy Duty Platform.   

We can design and manufacture probes or fixtures for the TA.XTplus texture analyser that are bespoke to your sample and its specific measurement.

Once your measurement is performed, our expertise in its graphical interpretation is unparalleled. Not only can we develop the most suitable and accurate method for the testing of your sample, but we can also prepare analysis procedures that obtain the desired parameters from your curve and drop them into a spreadsheet or report designed around your requirements.

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

TA.XTplus texture analyser with bloom jar 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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Watch our video about texture analysis Replicating Consumer Preferences
 Texture Analysis applications

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