The effect of moisture content on some mechanical properties of three varieties of pistachio nuts

Mechanical characteristics of agricultural crops are important to optimum design of milling، planting and harvesting machines and also for reducing losses and to improve quality of crops during harvest stage. In this study، mechanical properties of pistachio nuts (rupture force، deformation، rupture energy and toughness) were investigated. Mechanical properties were determined through quasi-static loading experiment using a material testing machine. A factorial experiment with completely randomized design was utilized to study the effect of moisture content (at 5 levels: 35، 30، 25، 20 and 15% w. b.)، loading rate (at 3 levels: 10، 20 and 30 mm min-1) and variety (at 3 levels: Fandoghi، Badami and Akbari) on mechanical properties of pistachio nuts. Results showed that all the three factors (variety، moisture content and loading rate) had significant effects on the rupture force، such that by decreasing moisture content the rupture force increased. Also، the nuts rupture force increased by increasing loading rate from 10 to 30 mm min-1. Investigation of the effects of variety، moisture content and loading rate on deformation، rupture energy and toughness showed that these factors had a significant effect on these parameters.