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

Tuesday, 25 March 2014

How materials testing can improve feed formulations when finances are tight

Panda with bamboo The pressure for improved quality is on for animal feed manufacturers the world over. Although selling prices are high, so too are overheads, as raw material and energy costs spiral.

Profits are tight and competition is intense, so it’s now more important than ever that feed mixers and compounders focus on optimising their products and differentiating their offering from that of their competitors. But how is this possible without pushing up production and processing costs even further?

Simply starting to use a new, expensive ingredient is not a decision that can be made quickly, and may not be possible at all in today’s economic climate. Improving economies of scale is valuable but challenging as competitors fiercely protect their own market share. The key lies in improving existing products and / or ascertaining the best ways to modify them. And now technology widely used in the food industry can help feed manufacturers do exactly that. 

Perfecting palatability
Animal feed must be carefully formulated to optimise both nutritional content and palatability – taste, smell and texture. The use of high quality ingredients is pointless if animals reject the feed. As a result, leading manufacturers already invest significant resources in determining the right combination of ingredients and processing techniques to develop their products.

Sensory testing is a common element of this process – just as it is in foods for human consumption. Complementing this with objective instrumental analysis provides a comprehensive insight into feed palatability and therefore the likely commercial success of the product.

Materials testing equipment
Multi-functional instruments – known as either materials testing instruments or Texture Analysers – can test ingredients, semi-finished and finished products, and even packaging. They can be fitted with different fixtures according to the product they are assessing and the type of test being conducted. These fixtures, each designed for a specific application, can be attached to the instrument’s base and / or horizontal arm. 

TA.HD Texture Analyser with Kramer Shear Cell attached
1: TA.HDplus Texture Analyser
Samples are placed on the base of the analyser or on the lower fixture, or held between the two fixtures. In a typical simple test, the instrument’s arm, which contains the loadcell, moves down to penetrate or compress the product and returns to its initial position according to the procedure specified in advance by the user. Suggested settings, test methods and typical examples, are usually provided for reference and training purposes.

During testing, data which characterises the product is collected as time, distance and force values, at a rate of up to 500 points per second. These values are typically plotted on a Force/Distance or a Force/Time graph and then analysed. The test results can be viewed in spreadsheet, chart or report format. Coefficients of variation (C.V.) account for variations between individual samples. Low C.V.s demonstrate reliability and accuracy of results.

Pellet durability and brittleness
As a large number of animal feeds are produced in pellet form, durability and brittleness are perhaps the most important product characteristics manufacturers can measure. Testing the durability (or hardness) of pellets can be carried out using a simple cylinder probe or compression platen like that shown in image 2. 

Compression test on feed pellets
2: Compression test on feed pellets
Bulk compression test using Ottawa call
3: Ottawa Cell
During this test, the instrument measures the force exerted to compress the pellet: the maximum force is interpreted as durability. If pellets fracture under this force, the area under the curve (see example in graph 1), knows as “work of compression”, is often a more meaningful parameter. Both measurements indicate how easily the animal will be able to chew the pellets.

More realistic results, however, can be achieved by performing a bulk compression test in an Ottawa Cell (see image 3), which has an averaging effect. Both these tests will also provide an indication of the pellet’s brittleness – which is defined as the number of peaks created during the compression process. Each peak denotes a fracture event and therefore quantifies brittleness.

Soft feeds

Cutting test on sausage
4: Knife blade cutting test
Durability testing is a valuable indicator of quality for pellets and other hard feeds, but soft feeds are more suited to cutting (see image 4) and puncture tests. Both these are commonly used in the food industry and are equally valuable in feed. Individual pieces or items can be sliced with a Warner-Bratzler Blade, or Volodkevich Bite Jaws can be used to imitate true biting action. Alternatively, for more realistic results, a Kramer Shear Cell tests multiparticle products in bulk (as seen in TA.HD image 1 above). Here, the force required to cut or shear through the sample reflects the ease with which the product can be chewed. Puncture tests, using a small cylinder probe, commonly around 3 mm in diameter will provide an indication of the sample’s softness.

Testing powders and grains
Like many other areas of industry, many products in the feed sector are powders or grains, or are made from powdered or granular ingredients. Because these particles are relatively small, they generally do not present problems during chewing or digestion. Instead, because they exhibit properties similar to both solids and liquids, they often behave unpredictably and irregularly during storage and handling. 

Powder Flow Analyser fitted to TA.XT plus
5: Powder Flow Analyser
This can result in non-uniformity (segregation) in blending, under- or over-dosage, inaccurate filling and inconvenient – and potentially expensive – obstructions and stoppages. Materials testing enables feed manufacturers and processors to measure and possibly predict powder / granule flow and avoid these common problems.

Farmers and producers are aware that some of the most common handling issues arise when conveying product from storage silos or bins into production, or into feeding troughs. Often the product will have been motionless for hours, days, or even weeks before it needs to move. Over this time, most powders and granules will compact under their own weight, making them much less free-flowing. On the other hand, powders used immediately after transport will have been aerated and flow more easily.

A range of tests is available for powders and granules. Using Stable Micro Systems’
TA.XTplus Texture Analyser in conjunction with a Powder Flow Analyser (see image 5), a blade or rotor is passed through the product situated in a transparent vessel. 

The blade moves vertically and rotationally, according to settings defined by the user, to conduct a specific test. Aerating or lifting the sample, for instance, can measure the cohesiveness (or “stickiness”) of the particles. Compaction provides a simple quality control test for variations between batches. Samples being compacted will resist flow and movement, so these tests will give an indication of the probability of caking.

Instruments like this can interpret and display this information in real time, as well as perform composite or statistical calculations. Tests on different samples, and tests conducted under differing conditions, can be compared quickly and simply to allow grading and ranking. As a result, powder and granule testing enables feed manufacturers to optimise the purchase of raw materials, improve processing efficiency, minimise waste and enhance product quality – before and after storage, packing and transportation.

Testing packaging


As the textural properties of the feed itself are crucial, so too is the performance of the packaging used. Bag films are strong and designed for heavy contents and vigorous handling, but a bag’s seals are often its weakest point. Seal failures result in wasted product and / or unwanted clean-up and repacking costs. 

Puncture test on Film Support Rig
6: Film Support Rig
Materials testing instrumentation can also be used to verify the strength of seals. Using adjustable Tensile Grips (as seen in the video), or Self-tightening Roller Grips, which avoid potential film slippage at the grip face, manufacturers can measure the force needed to open a seal. A lower force indicates a relatively weak seal, in which case they may choose to alter equipment settings, select a different bag or utilise a different sealing technology.

The strength of the packaging material itself can also be assessed using a Film Support Rig (image 6), which measures characteristics such as burst strength, resilience and relaxation properties. Such tests can be conducted by the packaging manufacturer or its customers.

In today’s competitive market, feed manufacturers need to be sure their products meet all customers’ requirements. Success depends on much more than nutritional content – the feed must process and handle well both within their own premises and on the farm. It must be able to withstand the rigours of transport and storage, yet still be palatable at the moment it is consumed. 

Materials testing tests, based on analyses routinely undertaken in the food industry, can help manufacturers stay ahead of competitors and grow their business. Such tests ensure that both the feed, and its packaging, reach the farmer in optimal condition and that the animals consume the nutrients they need - and enjoy them.

Stable Micro Systems also provide a number of other texture analysis fixtures suitable for assessing the physical properties of petfood and animal feeds.

Watch our video about testing of materials
 Putting Packaging to the Test
 Materials and Packaging Testing

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