Texture Profile Analysis 
Two Bites of TPA Test

Practical Definitions of Standard TPA Terms Paraphrased From

Dr. Malcolm Bourne's Food Texture & Viscosity (Academic Press). 

Hardness The hardness value is the peak force of the first compression of the product. The hardness need not occur at the point of deepest compression, although it typically does for most products.
Fracturability Not all products fracture; but when they do fracture the Fracturability point occurs where the plot has its first significant peak (where the force falls off) during the probe's first compression of the product. 
Cohesiveness Cohesiveness is how well the product withstands a second deformation relative to how it behaved under the first  deformation. It is measured as the area of work during the second compression divided by the area of work during the first compression. (Refer to Area 2/Area 1 in the below graph).
Springiness Springiness is how well a product physically springs back after it has been deformed during the first compression. The springback is measured at the downstroke of the second compression, so the wait time between two strokes can be relatively important.  In some cases an excessively long wait time will allow a product to springback more than it might under the conditions being researched (eg you would not wait 60 seconds between chews).

Springiness  is measured several ways, but most typically, by the distance of the detected height of the product on the second compression (Length 2 on the below graph), as divided by the original compression distance (Length 1). The original definition of springiness used the Length 2 only, and the units were in mm or other units of distance.  We do not subscribe to that original description of springiness since the springiness value can only be compared among products which are  identical in their original shape & height.  Many TPA users compress their products a % strain, and for those applications a pure distance value (rather than a ratio) is too heavily influenced by the height of the sample.  By expressing spriniginess as a ratio of its original height, comparisons can be made between a more broad set of samples and products.
Chewiness Chewiness only applies for solid products and is calculated as  Gumminess*Springiness (which is Length1/Length2). Chewiness is mutually exclusive with Gumminess since a product would not be both a solid and a semi-solid at the same time.
Gumminess Gumminess only applies to semi-solid products and is Hardness *Cohesiveness (which is Area 2/Area1). Gumminess is mutually exclusive with Chewiness since a product would not be both a semi-solid and a solid at the same time.
Resilience Resilience is how well a product "fights to regain its original position".  You can think of it as instant springiness, since resilience is measured on the withdrawal of the first penetration, before the waiting period is started. 

The calculation is the area during the withdrawal of the first compression, divided by the area of the first compression. (Area 5/Area4 on the below graph) Resilience is not always measured with TPA calculations, and was not a direct part of the original TPA work.  Resilience can be measured with a single compression, however, the withdrawal speed must be the same as the compression speed.

TPA Plots with Areas & Definitions
Note that your Post-test speed must be the same as your Test speed so that both compressions are plotted under identical circumstances, and the area integrations are fully comparable.
You only need the following three things to run TPA tests with Texture Expert:
  • A TPA two compression graph should be on the screen
  • A macro with TPA calculations should be in the Current Macro pull down box
  • A TPA results file should be active
All of these items, plus your graph preferences, can be established in a Project, which could be launched by the click of a button.

TPA Projects are comprised of:

  • test settings for the TPA test you want to use - so that the same desired type of test, the test speeds and distances all always available to the project
  • a graph preference file you want to use - so that the graphs are always plotted on the same conditions & scale.
  • a TPA macro you want to you use - so that the calculated forces, areas and distances are always made under the same conditions
  • a results file which has TPA calculations embedded

TPA test settings, macros, formulas and results files can be customized very simply.
Project
Common Questions on Analyzing TextureProfile Analysis Tests
The macro cannot find a third peak
  1. The product may not have actually fractured during the first compression- so no third peak will exist. Just click on OK.  You may modify the TPA macro so that it does not search for a fracture peak. 
The macro doesn't appear to find two distinct compressions
  1. The force may never return to zero between the two strokes, possibly because the product never separates from the probe as it withdraws at the end of the first compression (try increasing the GOTO force to a higher force than zero in the TPA macro) 
The macro does not mark Anchor #2 at the correct position @ the deepest point of compression
  1. The distance threshold is likely too low, and the macro cannot find the "peak" compression. If your force distance threshold is still at the 1.0 mm default then your product is probably very small, and you are compressing  it less than 1.0 mm. Try lowering the distance threshold (T'hold) from the F3 graph, Graph Preferences screen. 
The peaks are marked at the wrong position
  1. The graph may be jagged in between the two compressions (due to the product's behavior or sample jostling), or there may be a jagged second compression which will cause the macro to mark all three peaks too soon. Try inserting a Set Force Threshold command at the beggining of the macro (using high enough force threshold to ignore the jaggedness) to filter out the low force jaggedness which you may be encountering. 
The macro appears to calculate OK but you cannot see the  TPA values
  1. Look for the results file which is available from the Windows pull down menu. Look for the file option which has an .RES extension; if you are running the default TPA project it will be #2 on the pull down menu. You can scroll through to the Results files by holding down the control key while you also press the TAB key. 
The macro calculates OK but the results file does not include springiness, cohesiveness, etc
  1. You are not using a TPA -style results file, possibly becaue you did not know you were supposed to, or you accidentally closed the TPA results file. Whenever any results file is closed a blank results file will be created by the program to accept calculated information. Open up the TPAFRAC.RES file which is in the Sapmples subdirectory and then re-run the TPA macro. All of the results will be correctly calculated and located in the TPAFRAC.RES file. 
WE RECOMMEND THAT YOU ESTABLISH A PROJECT FOR YOUR TPA WORK SO THAT YOUR TEST SETTINGS, MACROS, RESULTS FILES AND GRAPH SETTINGS WILL ALWAYS BE EXACTLY AS YOU WANT - EVERY TIME.
Texture Profile Analysis  - Bibliography

Bourne, M.C., J.C. Moyer, and D.B. Hand. 1966. Measurement of food texture by a universal testing machine. Food Technology. 20:522.

Bourne, M.C. 1976. Interpretation of force curves from instrumental texture measurements. In Rheology and TextureinFood Quality, ed. J.M. deMan, P.W. Voisey, V.F. Rasper, and D.W. Stanley, pp. 244- 274. Westport, CT: AVI Publ. Co.

Bourne, M.C., J.F. Kenny, J. Barnard. 1978. Computer-assisted readout of data from texture profile analysis curves. Journal of Texture Studies 9, 481.

Bourne, M.C. 1978. Texture profile analysis. Food Technology. 32:62- 66, 72.

Bourne, M. C. 1982. Food Texture and Viscosity. 330 pages. Academic Press, New York (reprinted 1994)

Bourne, M. C. 1993. Texture measurements in finished baked goods. Chapter 6, pp. 134-151 in Advances in Baking Technology, eds. B.S. Kamel and C.E. Stouffer. Blackie Academic and Professional, London and New York.

Breene, W.M. 1975. Application of texture profile analysis to instrumental food texture evaluation. Journal of Texture Studies 6:53- 82.

Brennan, J. G. & Bourne, M. C. 1994. Effect of Lubrication on the Compression Behaviour of Cheese and Frankfurters. Journal of Texture Studies, 25, 139-150.

Buckley, D.F., G.E. Timbers, M. Kloek, M.J.L. Lalonde. 1984. Texture profile analysis with curve smoothing using a personal computer system. Journal of Texture Studies. 15:247.

Friedman, H.H., J.E. Whitney, and A.S. Szczesniak. 1963. The Texturometer - - a new instrument for objective texture measurement. Journal Food Science, 28:390- 396.

Peleg, M., 1996, Texture profile analysis parameters obtained by an instron universal testing machine, Journal Food Science 41:721-723.

Shoemaker, C.F., J.I. Lewis, and M.S. Tamura. 1987. Instruments for rheological measurements of food. Food Technol. 41(3):80- 84.

Szczesniak, A.S. 1963. Classification of textural characteristics. Journal Food Science, 28:285-289.

Szczesniak, A.S. 1963. Objective measurements of food texture. Journal Food Science, 28:410- 420.

Szczesniak, A.S., M.A. Brandt, and H. Friedman. 1963. Development of standard rating scales for mechanical parameters of texture and correlation between the objective and the sensory methods of texture evaluation., Journal Food Science, . 28: 397.

Szczesniak, A.S. and D.W. Kleyn. 1963. Consumer awareness of texture and other food attributes. Food Technology 17:74.

Szczesniak, A.S. and K.W. Torgeson. 1965. Methods of meat texture measurement viewed from the background of factors affecting tenderness. Adv. In Food Res. 14:33.

Szczesniak, A.S. 1966 . Classification of textural characteristics. Food Research :385-389.

Szczesniak, A.S. 1968., Correlations between objective and sensory texture measurements. Food Technology 22:981.

Szczesniak, A.S. 1972. Instrumental methods of textural measurements. Food Technology 26(1):50.

Szczesniak, A.S. 1973. Instrumental methods of texture measurements. In Texture Measurements of Foods (A. Kramer and A.S. Szczesniak, eds.) pp. 71-108, D. Reidel Publishing Co., Dordrecht, Holland.

Szczesniak, A.S. 1987. Correlating sensory with instrumental texture measurements- - an overview of recent developments. Journal of Texture Studies 18:1- 15.

Szczesniak, A.S. 1995. Texture Profile Analysis- Methodology interpretation clarified, Journal Food Science, (Letters) 60: vii

Szczesniak, A.S. 1998., Sensory Texture Profiling - Historical and Sensory Perspectives. Food Technology Vol 52, No. 8, 52-57

Voisey, P.W. 1976. Instrumental measurements of food texture. In Rheology and Texture in Food Quality, ed. J.M. deMan, P.W. Voisey, V.F. Rasper, and D.W. Stanley, pp. 79- 141. Westport, CT: AVI Publ. Co.

 Voisey, P.W., and J.M. deMan. 1976. Applications of instruments for measuring food texture. In Rheology andTexturein Food Quality, ed. J.M. deMan, P.W. Voisey, V.F. Rasper, and D.W. Stanley, pp. 142- 243. Westport, CT: AVI Publ. Co.

NOTE - If you know of other articles which might be strong general references to possible users of  TPA analytical techniques, please do not hesitate to bring them to our attention for possible inclusion on this list.

Links to Web Sites Which Discuss Texture Profile Analysis Tests