Effects of moisture content and number of loadings on force relaxation behaviour of chickpea kernels
J. Khazaei 1
,  
 
 
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1
Department of Agricultural Technical Affairs, Aboureihan Higher Education Complex, University of Tehran, Pakdasht, Iran
2
Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB R3T 5V6, Canada
 
Int. Agrophys. 2005, 19(4): 305–313
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ABSTRACT
Basic rheological property (force relaxation) of a single kernel of chickpea under uni-axial compression was studied. Information on the force relaxation behaviour of chickpea kernels is not available. Meanwhile, no papers was found to study the effects of number of loadings on stress relaxation behaviour of grains and fruits. In this study the effects of moisture content and number of loadings were studied on force relaxation behaviour of chickpea kernels. The results showed that the chickpea kernels had a time dependent behaviour similar to other viscoelastic materials. The three-term Maxwell model with a maximum relative difference (MRD) of 5% and R2 higher than 0.997 was chosen as the best fit equation to the relaxation data. Moisture content had a decreasing effect on the first term of the three-term Maxwell model (F1, t1), but the number of loadings had an increasing effect on the first term of the Maxwell model. For all moisture contents and number of loadings, the grain tissue dissipates a major proportion of the initially applied force at a relatively slow rate. As the number of loading increases, the kernel becomes more elastic. Consequently, more force was required to maintain a certain deformation level. A master curve was proposed to determine the force relaxation behaviour of the chickpea kernels at moisture contents between 6.7 and 18% for 1 to 9 cycles of loadings. The Peleg and Pollak model was unsatisfactory for representing the relaxation force for chickpea kernels.
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