Determination of mechanical properties of potato flesh during storage

The mechanical properties of potato (Solanum tuberosum L.) in various treatments including: three different varieties (Agria, Satina and Caesar), ten levels of storage time (22 weeks), and three levels of loading direction were presented in this study by conducting 270 uniaxial compression tests. The tests were performed on potato flesh in real conditions of storage. The measurements were done every 15 days during 22 weeks and analyzed based on a completely randomized design in 3 replications. Cylindrical test specimens with a 10 mm diameter and 20 mm length were used. According to the results, the effect of storage time and cultivar and interaction of time × cultivar on mechanical parameters (including: maximum rupture stress and strain; stress and tangent elastic modulus of secondary bio-yield point, toughness, and the energy to rupture) were statistically significant on the level of 1%. No significant differences were observed due to the effect of loading direction on the strain, stress and tangent elastic modulus of primary bio-yield. The mean, maximum and minimum values of energy to rupture were 0.215, 0.270 and 0.170 mJ, respectively. In addition, the mean, maximum and minimum values of tangent modulus at 0.02 strains were 2.523, 2.993 and 2.115 MPa, respectively. A third-degree polynomial best fitted the Stress-Strain curves in an axial compression test (R = 0.982: 0.999). The results of this study revealed that determination of modulus of elasticity of potatoes in axial compression testing was significantly influenced by testing conditions.