ISSN 1392-3196 Zemdirbyste-Agriculture Vol. 103, No. 2 (2016) 183 ISSN 1392-3196 / e-ISSN 2335-8947 Zemdirbyste-Agriculture, vol. 103, No. 2 (2016), p. 183‒192 DOI 10.13080/z-a.2016.103.024 Physical and chemical properties of soybean seeds determine their susceptibility to mechanical damage Piotr KUŹNIAR 1 , Ewa SZPUNAR-KROK 1 , Pavol FINDURA 2 , Jan BUCZEK 1 , Dorota BOBRECKA-JAMRO 1 1 University of Rzeszow Zelwerowicza 4, 35-601 Rzeszów, Poland E-mail: pkuzniar@ur.edu.pl 2 Slovak University of Agriculture in Nitra Andreja Hlinku 2, 949 76 Nitra, Slovakia Abstract The research was carried out to determine the infuence of the chemical composition and moisture content in seeds from selected soybean cultivars on their mechanical properties. The individual seeds were investigated at fve moisture contents in the conditions of quasi-static loads with the use of a Zwick universal testing machine. Mechanical properties of the soybean seeds from the analyzed cultivars depended on their chemical composition and moisture content. The seeds of the cv. ‘Herta PZO’ ruptured when the signifcantly smallest amount of the rupture force (105.6 N) was applied and were most prone to deformation (29.2%). The seeds of the cv. KS-40 were signifcantly less prone to deformation (16.7%) and ruptured with the smallest amount of energy (71.5 mJ) applied. The cv. ‘Petrina’ required the signifcantly highest amount of force (140.6 N) necessary for seed rupture, while the signifcantly highest modulus of elasticity (1721 MPa) was observed in the cv. SP-16. The cv. ‘Aligator’ required application of the signifcantly highest amount of energy (142.7 mJ). An increase in the moisture content in seeds caused a signifcant decrease in the rupture force and modulus and an increase in deformation and energy. Soybean seeds with higher protein and ash content ruptured when higher force was applied and were characterised by a higher modulus of elasticity, smaller extent of deformation and lower energy, being therefore more resistant to damage. Soybean seeds containing more fat and fbre were more prone to damage. Together with the increase in the moisture content (7–19%), we observed a decrease in the impact of the chemical components analyzed on the rupture force and the modulus of elasticity. At the same time we observed an increase in the infuence of the tested components on deformation and energy. Key words: chemical composition, mechanical properties, moisture content. Introduction Soybean (Glycine max (L.) Merrill) is a particularly good source of protein (35–42%) and fat (16–27%). This makes the soybean one of the most valuable and most commonly cultivated crops (Kumar et al., 2006). The soybean shares the faw of many plants from the Fabaceae family, namely it is prone to mechanical damage occurring during threshing, cleaning, drying, transportation, storage and processing. Knowledge of the physical properties of soybean seeds is therefore particularly important for the optimization of harvesting, drying and storing processes, as it translates into minimization of losses and mechanical damage (Rybiński et al., 2009). Unlike cereal grains, soybean seeds have two cotyledons between which a gap may be formed if the water content is low. This leads to an increased susceptibility of the seeds to damage like, for example, breaking in half (Shahbazi et al., 2011 a; Dobrzański, Stępniewski, 2013). The moisture content in seeds strongly infuences the occurrence of mechanical damage, affecting elasticity and resistance in both cotyledons and the seed coat (Sosnowski, Kuźniar, 1999; Shao et al., 2007; Szwed, Łukaszuk, 2007; Shahbazi et al., 2011 a; b). Optimum moisture content at which the mechanical damage of seeds determined in the conditions of dynamic loads was minimum (Sosnowski, Kuźniar, 1999) and germination percentage was maximum (Divsalar, Oskouei, 2011) is 13–15%. This stems from a very complex seed structure (Moïse et al., 2005). The process of crushing is strongly infuenced by soybean seed elasticity and viscosity. Seed elasticity plays an important role in the frst stage of crushing, and its viscosity – in the subsequent stages (Dobrzański, Stępniewski, 2013). The occurrence of damage also depends on the size and shape of seeds as well as seed coat thickness and chemical composition (Capeleti et al., 2005; Rybiński et al., 2013). Karaj and Müller (2010) and Dobrzański and Stępniewski (2013) demonstrated that seed resistance to mechanical damage