Stress Relaxation of Date at Different Temperature and Moisture Content of Product: A New Approach

Authors: D. Zare, M. Alirezaei, S.M. Nassiri

Abstract:

Iran is one of the greatest producers of date in the world. However due to lack of information about its viscoelastic properties, much of the production downgraded during harvesting and postharvesting processes. In this study the effect of temperature and moisture content of product were investigated on stress relaxation characteristics. Therefore, the freshly harvested date (kabkab) at tamar stage were put in controlled environment chamber to obtain different temperature levels (25, 35, 45, and 55 0C) and moisture contents (8.5, 8.7, 9.2, 15.3, 20, 32.2 %d.b.). A texture analyzer TAXT2 (Stable Microsystems, UK) was used to apply uniaxial compression tests. A chamber capable to control temperature was designed and fabricated around the plunger of texture analyzer to control the temperature during the experiment. As a new approach a CCD camera (A4tech, 30 fps) was mounted on a cylindrical glass probe to scan and record contact area between date and disk. Afterwards, pictures were analyzed using image processing toolbox of Matlab software. Individual date fruit was uniaxially compressed at speed of 1 mm/s. The constant strain of 30% of thickness of date was applied to the horizontally oriented fruit. To select a suitable model for describing stress relaxation of date, experimental data were fitted with three famous stress relaxation models including the generalized Maxwell, Nussinovitch, and Pelege. The constant in mentioned model were determined and correlated with temperature and moisture content of product using non-linear regression analysis. It was found that Generalized Maxwell and Nussinovitch models appropriately describe viscoelastic characteristics of date fruits as compared to Peleg mode.

Keywords: Stress relaxation, Viscoelastic properties, Date, Texture analyzer.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1082491

References:

[1] J. S. Sidhu, "Date fruits production and processing. In Handbook of fruit and fruit processing," Blackwell Publishing, 2006.
[2] N. N. Mohsenin, "Physical properties of plant and animal materials,"Amsterdam: Gordon and Breach, 1986.
[3] M. A. Del Nobile, S. Chillo, A. Mentana, A. Baiano, "Use of the generalized Maxwell model for describing the stress relaxation behavior of solid-like foods," Journal of Food Engineering, vol. 78, pp. 978-983, 2007.
[4] P. P. Lewicki,. "Rheological properties of raisins,": Part I: compression test. Journal of Food Engineering, vol. 24, pp. 321-338, 1995.
[5] S. Kajuna, W. K. Bilanski, G. S. Mittal, "Effect of ripening on the parameters of three stress relaxation models for banana and plantain," ASAE, vol.14 (1), pp. 55-61, 1998.
[6] M. Fincan, P. Dejmek, "Effect of osmotic pretreatment and pulsed electric field on the viscoelastic properties of potato tissue," Journal of Food Engineering, vol. 59, pp. 169-175, 2003.
[7] B. H. Hassan, A. M. Alhamdan, A. M. Elansari, "Stress relaxation of dates at Khalal and Rutab stages of maturity," Journal of Food Engineering, vol. 66, pp. 439-445, 2005.
[8] J. Lu, J. Tan, P. Shatadal, D. E. Gerrard, "Evaluation of pork color by using computer vision," Meat Science, vol. 56, pp. 57-60, 2000.
[9] T. Brosnan, D. W. Sun, "Improving quality inspection of food products by computer vision--a review," Journal of Food Engineering, vol. 61, pp. 3-16, 2004.
[10] D. J. Lee, R. Schoenberger, J. Archibald, S. McCollum, "Development of a machine vision system for automatic date grading using digital reflective near-infrared imaging," Journal of Food Engineering, vol. 86, pp. 388-398, 2008.
[11] R. Chinchuluun, W. S. Lee, R. Ehsani, "Machine vision system for determining citrus count and size on canopy shake and catch harvester," ASABE, vol. 25 (4), pp. 451ÔÇÉ458, 2009.
[12] Anonymous, Commodity production. Retrieved 2012, from http://faostat.fao.org/site/339/default.aspx, 2010.
[13] K. M. Waananen, M. R. Okos, "Stress relaxation properties of yellowdent corn kernels under uniaxial loading," ASAE, vol. 35 (4), pp. 1249- 3504, 1992
[14] J. F. Steffe, "Rheological methods in food processing engineering," East Lansing, MI, USA: Freeman Press, 1992
[15] A. Nussinovitch, M. Peleg, M. D. Normand, "A modified Maxwell and a non exponential model for characterization of the stress relaxation of agar and alginate gels," Journal of Food Science, vol. 54(4), pp.1013- 1016, 1989.
[16] M. Peleg, K. Pollak, "The problem of equilibrium conditions in stress relaxation analysis of solid foods. Journal of Texture Studies," vol. 13, pp. 1-11.
[17] L. Greenspan, "Humidity fixed points of binary saturated aqueous solutions," Journal of Research of the National Bureau of Standards, vol. 81(A) (1), pp. 89-96, 1982.
[18] T. D. Hong, R. H. Ellis, J. Gunn, D. Moore, "Relative humidity, temperature, and the equilibrium moisture content of conidia of Beauveria bassiana (Balsamo) Vuillemin: a quantitative approach," Journal of Stored Products Research, vol. 38, pp. 33-41, 2002.
[19] D. Zare, S.Minai, M. Mohamad Zadeh, M. H. Khoshtaghaza, "Computer Simulation of Rough Rice Drying in a Batch Dryer," Energy Conv. & Mang. vol. 47, pp. 3241-3254, 2006.
[20] P. Lewicki, W. Wolf, "Rheological Properties of Raisins," Part II. Effect of Water Activity. Journal of Food Engineering, vol. 26 (1), pp. 29-43, 1995.
[21] R. M. Myhara, M. S.Taylor, B. A. Slominski, I. Al-Bulushi, "Moisture sorption isotherms and chemical composition of Omani Dates," Journal of Food Engineering, vol. 37, pp. 471-479, 1998.