Investigation of the effect of ohmic heat treatment on some mechanical properties of closed pistachio

Document Type : Research Article


1 Associate Professor, Department of Bio-System Mechanical Engineering, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.

2 M.Sc Student Department of Bio-System Mechanical Engineering, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.


The purpose of this investigation was to study smiling of three varieties pistachio mouths, Akbari, Ahmad Aghayi and Fandoghi with help of ohmic heating treatment. In this research, the effect of pistachio varieties (Akbari, Ahmadaghaye and Fandoghi), loading direction(vertical and horizontal) and ohmic time (3, 6 and 9 minutes) on mechanical properties of pistachio, including breaking energy, maximum force, breaking strength, toughness and power consumption were investigated and the results were analyzed in a completely randomized design with three replications using SAS software. The results showed that amount of ohmic time and loading direction for maximum force, breaking energy, toughness and breaking strength were statistically significant and the varietie was meaningful only for energy and failure force. None of the factors was significant for power consumption. Also, with increasing the ohmic time, the value of the maximum force of Akbari, Ahmad Aghaei and Fandoghi varieties were from 3112.6, 303.75, 261.76 (for control), to 125.76, 138.68, 189.65 N. Similarly, the pistachio varieties for breaking energy from 384.95, 300.3, 228.06J to 139, 120.9, 18.14 J, and the and breaking strength of 6.84, 6.99, and 7.33 N .m2 to 2.80, 5.40 and 4.92 N.m2 and finally for the toughness of 0.353, 0.343 and 0.247 J.m3 to 0.167, 0.247 and 0.220 J .m3 which is achieved at the ohmic time of 9 minutes. Also, with vertical loading, the failure force was lower than the horizontal position. In ohmic heating with the time of 9 minutes, the minimum failure force was obtained. The times of 6 and 3 minutes had a greater failure force.

Graphical Abstract

Investigation of the effect of ohmic heat treatment on some mechanical properties of closed pistachio


  • Variety, ohmic heating time and direction are important factors in breaking pistachio shell.
  • With increasing ohmic heating time and, moisture content, less force is required to break the pistachio shell.
  • Samples in the vertical direction require less force to break the pistachio shell than the horizontal direction.
  • Load direction, has had a more significant effect on energy and pistachio resistance.
  • The use of the ohmic heating method has a positive effect on reducing the failure force.


Main Subjects

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