As the food industry has improved the quality of its products, so consumer awareness has grown and now demands further improvements. Attractive visual appearance is vital, being the first contact between buyer and product. Then smell and texture, as the food enters the mouth, followed by flavour as the food is eaten. Eric Russell reports.
In the area of texture analysis, developments are being made not only to further improve quality but to ensure that consumer expectations are fulfilled. This includes defining the language of texture. Words such as crunchy, soft, crisp are subjective and can mean different things to different people.
The meaning also depends on the type of food being described and its audible characteristics. Would an eater describe an apple as crunchy if there were no sound when it was bitten, for example.
To measure the texture of foods requires an understanding of fracture mechanics and the stages that food passes through as it comes under increasing pressure in the mouth. By subjecting a sample to known conditions of stress and strain in a controlled manner, its mechanical characteristics can be interpreted. These can be displayed as a deformation curve that shows the response of the sample.
If the sample is cycled through compression and relaxation, simulating chewing, then a chewiness or gumminess factor can be calculated from the total energy taken by the testing machine. The sample is cycled until its compressive properties match those of a sample that has been chewed by a human until it was ready for swallowing.
In general, it is felt that the food industry as a whole is not utilising texture analysis to its full potential as a rheological indicator.
Instrument suppliers
CNS Farnell's texture analyser was designed by Leatherhead Food Research Association and is portable and flexible. The LFRA TA Computer Interface helps realise the full potential of the instrument. This easy to operate computer program permits the analysis of load versus time graphs with manually positioned cursors.
The company also offers the QTS25 texture analyser which is also known as the aStevens'. This flexible materials testing system provides valuable data on an ever increasing range of texture parameters. It represents the latest generation of texture testing instruments and uses the concepts originally established by Leatherhead FRA.
The Model 5542 from Instron provides complete automation of the texture profile analysis (TPA) test in conjunction with the company's Merlin software. It offers a choice of load cells and will interface with any PC.
A range of extra fittings is available and Instron says that Stratford-Upon-Avon Foods (SonA) uses a custom made anvil to replicate the biting action on a variety of foods.
SonA is one of the UK's leading suppliers of pickled products and says a key problem is ensuring that pickled beetroot has an acceptable texture for eating. This can be a technical minefield but in conjunction with one of its customers and Instron, it has successfully developed a test that gives customers accurate information on how the beetroot is affected during the cooking process.
Using an Instron 5542 testing system with Merlin software, SonA technologists can now carry out compression tests to simulate the human action of biting through a slice of beetroot. This results in a big improvement in data accuracy compared to the older and less reliable method of crushing the product through a tenderometer.
As the anvil cuts through the centre of a slice of beetroot the test measures compression in kilograms and displays the results instantly in graphical form on the computer screen. SonA is now introducing other products such as gherkins and onions to compression bite testing.
Instron offers three ranges of control electronics matched to specific software packages. The 5800 is Instron's most capable and flexible controller for the most demanding materials testing applications and programs. The 5500 is the most widely used controller for use on advanced materials testing applications. The 4400 controller is designed for use on a wide range of general purpose testing applications.
New product
Lloyd Ametek has just unveiled its TAPlus, a new, affordable, high performance digital texture analyser aimed at driving down the costs of quality testing in food manufacture.
Designed for both routine textural testing and sophisticated texture profile analysis, the instrument is very easy to use. It features a large working area to accommodate large samples and a novel modular design so customers can build a solution to match their exact needs and budget.
Performance is enhanced further through the company's Nexygen MT software and a wide range of food texture probes, jigs and attachments. These include a comprehensive series of multi-purpose grips suitable for testing food packaging.
Typical applications for TAPlus include measuring gelatine Bloom strength to BS757; dough firmness; softness measurement, crumb strength and shelf life of baked items; cutting forces of bread, meat and butter; fracture properties of biscuits and confectionery; and the tensile strength and compressibility of cooked spaghetti under cycling.
Ametek's comprehensive Nexygen MT test and data analysis software is Windows based and features a library of international standard tests and specialist food test set-ups. These include a fatigue cyclic test for measuring the recovery properties of a sample which is not expected to rupture; and a four point gel test to measure the four parameters of a gel, Bloom, break load, modulus and work done to break. Results can be exported easily into other packages for flexible and comprehensive reporting.
Other standard test set-ups include a single hardness test; single stickiness test to measure the adhesiveness and adhesive force of a sample; snap strength test; a stress relaxation test setup for measuring the relaxation of a sample while compressed for a length of time; and the Texture Profile Analysis setup to measure the hardness, cohesiveness, springiness, gumminess, chewiness, fracture force, adhesive force, adhesiveness and springiness index of a food sample.
Stable Microsystems offers its TA.XT2i which tests in both compression and tension on a cycling basis. It offers a choice of load cells and has built in protection to avoid damage from full-speed impacts.
The computer system offers pre-programmed test facilities and stores 50 test procedures. Options include extra software packages, probes and attachments.
These products will transform the art of describing food texture into a science and help avoid consumer
disappointment, a sales
problem that has long
lasting repercussions for
all industries. p
