Innovations in Texture Analysis

The texture of natural and/or functional food items is every bit as important as for standard process foods. Consumers would certainly complain if an apple was not juicy, or tomatoes were soft. Scientific texture analysis allows reproducible, scientific measurements to be made of these parameters. Texture testing is a well-established technique for evaluating the physical properties of raw ingredients and food structure. For naturally grown products such as fruit and vegetables, these techniques can be used to evaluate different growing conditions, time of harvest and storage conditions. It can also be used to compare the properties of genetic variants. Many fresh fruits and vegetables are supplied to supermarkets pre-packaged, so investigations can be carried out on the effects of packaging on textural properties, shelf life and even packaging for safe transit.

Since texture is a characteristic relating to the sense of touch, it is a property that can be measured easily by mechanical methods in units such as force. In texture testing, standard tests such as compression, tension and flexure are used to measure hardness, crispiness, crunchiness, softness, springiness, tackiness and other properties, many of which are appropriate for fruit and vegetables. Comparison of the results from mechanical texture analysis with trained human sensory panels has shown that the measurements have a high correlation with the various sensory attributes associated with textural quality.

Mechanical texture analysis, using a properly calibrated texture tester run by software using fundamental algorithms removes all elements of subjectivity from the testing. Instrumental testing allows standards to be introduced and followed and provides full documentation of the test procedures. One example of a high-performance food texture analyzer is the Lloyd Instruments TAPlus. The 220 lbf (102 Kgf, 1000N) capacity TAPlus is designed for both routine and sophisticated texture analysis, using the companys latest NEXYGENPlus materials test and control software.

A large range of specially engineered jigs, probes and fixtures are available for a wide variety of food texture testing applications. Grips and fixtures come in a variety of sizes, gripping surfaces, styles and capacities. Many of the tests have been standardized. The Volodkevitch Bite Set fixture, for example, is designed to imitate incisor teeth shearing through vegetables, fruit and other crispy or crunchy food products. The set comprises upper and lower teeth, which are brought together during the test until almost touching. The sample is positioned on the lower tooth, and the result is measured as the peak force required to bite through the sample. Results correlate with tenderness, toughness and firmness of the sample. Puncture and penetration tests are important for testing the firmness of fruit and vegetables.

In addition to the many standard tests that utilize the described fixtures, many researchers will want to develop their own tests. Fixtures that offer the versatility to create and conduct the appropriate test are available, and some companies even have the ability to design and manufacture special jigs. With the added capabilities of evaluating packaging materials, texture analysis is a powerful tool for determining the quality of natural foods. 

Angel Schell is the manager of marketing communications for Albany, N.Y.-based AMETEK Test & Calibration Instruments Americas. The company can be contacted at [email protected] or online at www.lloyd-instruments.com.