Poisson’s ratio of pumpkin seeds and their kernels as a function of variety, size, moisture content and loading rate

Abstract

In this study, the Poisson’s ratio of two varieties of Iranian pumpkin seeds and their kernels (namely Zaria and Gaboor) was determined as a function of moisture content (4%, 7.8%, 14% and 20% d.b.), size (small, medium, large) and loading rate (2, 5, 8 and 10 mm/min).  Pumpkin seeds and their kernel were quasi-statically loaded in horizontal and vertical orientations.  The results showed that Poisson’s ratio of pumpkin seeds and their kernels decreased with increasing moisture content for the varieties under study while it increases with increasing loading rate.  Average Poisson’s ratio values  decreased from 0.347 to 0.267 and from 0.421 to 0.348 when the moisture levels increased from 4% to 20%, for seeds of Zaria and Gaboor varieties, respectively.  Poisson’s ratio values for corresponding kernels ranged from 0.252 to 0.330 and 0.345 to 0.417.  When the loading rate increased from 2 to 10 mm/min, average values of Poisson’s ratio increased from 0.272 to 0.420 for seeds and from 0.26 to 0.41 for kernel, respectively.  Investigating the effect of size revealed that Poisson’s ratio of pumpkin seeds and its kernel increased as the average size of the samples increased.  Finally, values of the studied parameters play a key role in minimizing losses during hulling of pumpkin seeds.  Therefore, by applying the results of this study, the cost of hulling process is reduced, or the effectiveness of this industry will be increased.

Keywords: pumpkin seeds, elasticity theory, engineering properties, Poisson’s ratio, hulling process