Verification of the Peleg and Normand Equation at Varied Loads and Moisture During Stress Relaxation of Wheat

Main Article Content

Grzegorz Łysiak
Ryszard Kulig
Ryszard Kulig


Wheat kernel is made up of structures of different apparent viscosities with varied ability to withstand stress and dissipate strain energy. Its complex mechanical behaviour determines technological susceptibility and is important for wheat quality assessment. The aim of the study was the examination of the Peleg and Normand model to characterize the overall stress relaxation behaviour of wheat kernel at varying loading conditions. The relaxation experiments were made with a help of a universal machine Zwick Z020 in compression at four distinct initial load levels, i.e., 20, 30, 40, and 50 N. The measurements were made for intact wheat kernels at seven levels of moisture content. Relaxation characteristics were approximated with the help of Peleg and Normand formula. An interactive influence of the load level and moisture on Peleg and Normand constants have been confirmed. The initial loading level had none or only slight effect on the model coefficients (Y(t), k1 and k2). The parameters of the Peleg and Normand model decreased with the increase of water content in kernels. For moist kernels, a higher amount of absorbed compression energy was relaxed, since less energy was necessary to keep the deformation at a constant level.

Article Details

How to Cite
Łysiak, G., Kulig, R., & Kulig, R. (2019). Verification of the Peleg and Normand Equation at Varied Loads and Moisture During Stress Relaxation of Wheat. Agricultural Engineering , 23(3), 89-99.


Al Aridhee, J., Łysiak, G. (2015). Stress relaxation characteristics of wheat kernels at different moisture. Acta Scientarum Polonorum, Technica Agraria, 14(3-4), 3-10.

ASAE 368.4. Compression Test of Food Materials of Convex Shape. (2006). St. Joseph, MI (USA): American Society of Agricultural and Biological Engineers, (ASABE), 554-556.

Bargale, P.C., Irudayaraj, J. (1995). Mechanical strength and rheological behavior of barley kernels. Internaional Journal of Food Science and Technology, 30(5), 609-623.

Buňka, F., Pachlová, V., Pernická, L., Burešová, I., Kráčmar, S., Lošák, T. (2013). The dependence of Peleg's coefficients on selected conditions of a relaxation test in model samples of edam cheese. Journal of Texture Studies, 44(3), 187-195.

Dell Inc. Dell Statistica (data analysis software system). Version 13., 2016.

Faridi, H., Faubion, J.M. (2012). Dough rheology and baked product texture. Springer Science & Business Media.

Filipčev, B.V. (2014) Texture and stress relaxation of spelt–amaranth composite breads. Food and Feed Research, 41(1), 1-9.

Gunasekaran, S., Ak, M.M. (2000). Dynamic oscillatory shear testing of foods-selected applications. Trends in Food Science and Technology, 11(3), 115-127.

Guo, L., Wang, D., Tabil, L.G., Wang, G. (2016). Compression and relaxation properties of selected biomass for briquetting. Biosystems Engineering, 148, 101-110.

Guo, Z., Castell-Perez, M.E., Moreira, R.G. (1999). Characterization of masa and low–moisture corn tortilla using stress relaxation methods. Journal of Texture Studies, 30(2), 197-215.

Hatcher, D.W., Bellido, G.G., Dexter, J.E., Anderson, M.J., Fu, B.X. (2008). Investigation of uniaxial stress relaxation parameters to characterize the texture of yellow alkaline noodles made from durum and common wheats. Journal of Texture Studies, 39(6), 695-708.

Herak, D., Kabutey, A., Choteborsky, R., Petru, M., Sigalingging, R. (2015). Mathematical models describing the relaxation behaviour of Jatropha curcas L. bulk seeds under axial compression. Biosystems Engineering, 131, 77-83.

Karaman, S., Yilmaz, M.T., Toker, O.S., Dogan, M. (2016). Stress relaxation/creep compliance behaviour of kashar cheese: Scanning electron microscopy observations. International Journal of Dairy Technology, 69(2), 254-261.

Karim, A.A., Norziah, M.H., Seow, C.C. (2000). Methods for the study of starch retrogradation. Food Chemistry, 71(1), 9-36.

Khazaei, J., Mann, D. (2004). Effects of temperature and loading characteristics on mechanical and stress–relaxation behavior of sea buckthorn berries. Part 2. Puncture Tests. Agricultural Engineering International: CIGR Journal.

Khazaei, J., Mann, D. (2005). Effects of moisture content and number of loadings on force relaxation behavior of chickpea kernels. International Agrophysics, 19(4), 305-313.

Lewicki, P. (2004). Water as the determinant of food engineering properties. A review. Journal of Food Engineering, 61(4), 483-495.

Lewicki, P., Łukaszuk, A. (2000). Changes of rheological properties of apple tissue undergoing convective drying. Drying Technology, 18(3), 707-722.

Lewicki, P., Spiess, W.E. (1995). Rheological properties of raisins: Part I. Compression test. Journal of Food Engineering, 24(3), 321-338.

Łysiak, G. (2007). Influence in of moisture on rheological characteristics of the kernel of wheat. Acta Agrophysica, 9(1), 91-97.

Mandala, I., Karabela, D., Kostaropoulos A. (2007). Physical properties of breads containing hydrocolloids stored at low temperature. I. Effect of chilling. Food Hydrocolloids, 21(8), 1397-1406.

Ozturk, O.K., Takhar, P.S. (2017). Stress relaxation behavior of oat flakes. Journal of Cereal Science, 77, 84-89.

Peleg, M. (1980). Linearization of relaxation and creep curves of solid biological materials. Journal of Rheology, 24(4), 451-463.

Peleg, M., Normand, M.D. (1983). Comparison of two methods for stress relaxation data presentation of solid foods. Rheologica Acta, 22(1), 108-113.

Shelef, L., Bousso, D. (1964). A new instrument for measuring relaxation in flour dough. Rheologica Acta, 3(3), 168-172.

Shiau, S.Y., Chang, Y.H. (2013). Instrumental textural and rheological properties of raw, dried, and cooked noodles with transglutaminase. International Journal of Food Properties, 16(7), 1429-1441.

Shiau, S.Y., Wu, T.T., Liu, Y.L. (2012). Effect of the amount and particle size of wheat fiber on textural and rheological properties of raw, dried and cooked noodles. Journal of Food Quality, 35(3), 207-216.

Singh, H., Rockall, A., Martin, C.R., Chung, O.K., Lookhart, G.L. (2006). The analysis of stress relaxation data of some viscoelastic foods using a texture analyzer. Journal of Texture Studies, 37(4), 383-392.

Sozer, N., Dalgic, A. C. (2007). Modelling of rheological characteristics of various spaghetti types. European Food Research and Technology, 225(2), 183-190.

Sozer, N., Kaya, A., Dalgic, A.C. (2008). The effect of resistant starch addition on viscoelastic properties of cooked spaghetti. Journal of Texture Studies, 39(1), 1-16.

Wu, M.Y., Chang, Y.H., Shiau, S.Y., Chen, C.C. (2012). Rheology of fiber–enriched steamed bread: stress relaxation and texture profile analysis. Journal of Food and Drug Analysis, 20(1), 133-142.

Most read articles by the same author(s)