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ADM Milling - testing texture for technological milling

Figure 1:  ADM Milling measures dough extensibility using a Kieffer Dough & Gluten Extensibility Rig on the TA.XTplus.

As the largest independent flour miller in the UK, ADM Milling has been supplying the bakery and food manufacturing sectors with high quality flours and flour-based blends since 1999.

Processing around one million tonnes of wheat per annum, the company supplies customers ranging from multinational manufacturers to in-store bakeries, caterers and craft bakers across the UK and Republic of Ireland.

Operating in this dynamic market, with a broad customer base and high volumes, quality flour is crucial. Accurate, reliable QC systems are therefore a prerequisite. With this in mind, ADM Milling recently upgraded its texture analysis equipment - a key part of the quality control process. This has enabled the company to benefit from the flexibility to design tests which investigate specific parameters of interest, as well as improved data processing.

Upgrading for more precise analysis

The new generation instrument from Stable Micro Systems, the TA.XTplus, replaced the previous TA.XT2i texture analyser in place at the company. ADM Milling requires accurate measurement data on the performance of its flours in three key areas; dough extensibility, bread firmness and pasta texture. The new instrumentation not only fulfills these requirements but also delivers the added benefit of allowing the company to develop its own unique test procedures.

Dough extensibility

Dough extensibility is an important measurement in bakery for pre-determining the rise qualities and structure of the finished product which can be affected by homogenisation, long relaxation times or the addition of salts, emulsifiers and oxidants. Using the Kieffer Dough & Gluten Extensibility Rig attachment (see Figure 1) on the TA.XTplus, the dough's resistance to extension (maximum force) and extensibility (distance to break) are measured. Samples are divided into identical test sections which are left to relax and then laid onto a grooved plate. This is then placed into a spring-loaded clamp secured to the texture analyser. When the tensile test commences, a hook probe rises, extending the dough sample until it breaks.

Figure 2:  ADM Milling measures the firmness and stickiness of cooked pasta on the TA.XTplus.

Test results reveal that different varieties of wheat have a markedly different effect on dough extensibility. Using the TA.XTplus therefore allows ADM Milling to determine which kinds of wheat are best suited for different types of flour and, therefore, different end-products. For example, a bread-making dough requires a great deal of extensibility, whereas this would be a negative attribute for biscuits.

Bread firmness

Measuring bread firmness is another important consideration for ADM Milling. As consumers become more selective in their choice of products and often perceive softer bread to be fresher, manufacturers are increasingly looking for the highest quality flour to provide them with optimum results. Bread firmness analysis using the TA.XTplus forms an essential part of the company's ongoing monitoring of its products, with tests performed weekly to ensure that any changes in grist or processing do not adversely affect the high quality of its flours. This enables ADM Milling to guarantee consistency for its customers.

Standard firmness tests involve a flat, circular plate being lowered onto a sample slice of bread, which is then compressed while a load cell contained in the texture analyser's horizontal arm measures the force. With the upgrade to the TA.XTplus, Stable Micro Systems' Exponent software has enabled ADM Milling to develop a specially designed test method to also analyse the recovery of bread after initial testing. Once the standard test is complete, the probe is lowered once more to measure the height of the sample following compression. This is compared to the height immediately before compression to indicate the recovery of the bread, which would typically stand at around 97%.

This additional testing provides ADM Milling with data which gives a more complete description of loaf texture, as it allows the company to also establish the resilience of the slice. This is important in terms of how well the loaf would withstand the spreading of butter, for example, or whether it would stick to the roof of the mouth. Using this specially-designed test, ADM Milling can establish exactly what proportions of ingredients are needed to create a top quality loaf with high recovery. This property is affected by the inclusion of different additives, such as enzymes or improvers, or the use of different wheat varieties, which affect crumb texture. This is an example of the unique test procedures facilitated by the TA.XTplus.

Pasta texture

ADM Milling also tests pasta firmness and stickiness. Using Stable Micro Systems' pasta firmness / stickiness rig, strands or sheets of pasta are held on the TA.XTplus by a support block which includes a rectangular cut-out exposing the sample (see Figure 2). A corresponding rectangular compression plate, connected to the loadcell, is lowered to test the firmness of the pasta during the compression stroke, and its stickiness upon withdrawal.

The company recently adapted this test method in order to investigate specific parameters of interest to a customer, which wished to develop a firmer noodle. By analysing the textural effect of changes to the grist and processes, ADM Milling has been able to make recipe and process suggestions to increase the firmness of the product.

The ability to devise tests according to customers' needs is regarded as a key advantage of the upgrade by ADM Milling. The company is now able help customers effectively manage changes to processes or ingredients and also to solve problems, such as decreasing the rate of staling of products.

Technological advantages

ADM Milling found the facility to design testing programs to suit specific requirements a key advantage, while the improved software interface of the TA.XTplus is easy to use. Information such as capacity, calibration and serial numbers is also stored within the load cell and automatically detected upon installation, providing greater flexibility for the design of unique test procedures.

Improved data processing is also an important benefit. Data from each test can be recorded and interpreted with ease using Stable Micro Systems' 32-bit software, which provides consistently accurate and quantifiable textural information. This has allowed the company to benefit from the following:

The company is also able to take full advantage of the new flexibility offered by the texture analyser's improved electronics and mechanics. It now has the ability to programme individual arm-movement sequences at various speeds and distances. This enables the most complex test protocols to be established and allows exact measurements to be achieved. The new speed range of 0.01mm/s to 40mm/s on the TA.XTplus is also broader than the 0.1mm/s to 10mm/s range on the TA.XT2i instrumentation and ensures that all tests carried out could more closely mimic real-life performance. This enables more exact results and precise product analysis to be obtained.

Support from start to finish

ADM Milling worked closely with Stable Micro Systems to ensure a smooth hand-over during the upgrade and to integrate the TA.XTplus with its existing IT systems. As well as taking advantage of user training and technical advice, so staff could use the new system quickly and accurately, the company also receives ongoing support from Stable Micro Systems. It can download new firmware to the TA.XTplus from www.stablemicrosystems.com, which provides ongoing modifications and improvements to the software. ADM Milling can also take advantage of program and macro writing offered by Stable Micro Systems, should the company need a new test sequence or data analysis technique to be prepared.

According to John Cottrell, ADM Milling's Technical Director, upgrading to the TA.XTplus has brought tangible benefits to the company:

"We have had a great deal of experience with Stable Micro Systems' texture analysis equipment and have always been confident that it has provided us with objective and repeatable testing, and accurate, reliable results. The new generation instrumentation is even more efficient and, thanks to the facility to allow us to develop our own test procedures and improved data processing, has allowed us to achieve a real technological advantage in flour development.

"As a business we see Stable Micro Systems' protocol as essential in upholding our own rigorous quality standards. The TA.XTplus has enabled us to fully investigate the performance of our flours for a wide range of parameters and has increased our understanding of the complex role of flour in a large number of products. It also allows us to monitor our flours and ensure the consistent end-product quality demanded by manufacturers and consumers alike."

ADM Milling is a wholly owned subsidiary of the US company Archer Daniels Midland (ADM). It has ten wheat flour mills located around the UK and a technical centre in Avonmouth near Bristol. Using state-of-the-art milling technology to manufacture its products, it has earned a reputation as a highly technical miller.

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