Determination of Elastic Characteristics (Viscoelastic) in Two Potato Cultivars Stored in Non-Technical and Technical Storage

To determine the mechanical behavior (creep) of potato under constant load, two potato cultivars were stored in two different conditions and the effects of storage time and temperature were investigated on creep behavior of the samples. Creep parameters included instantaneous elastic coefficient, delay elastic coefficient, initial viscoelastic coefficient, delayed viscoelastic coefficient and delay time. Two samples showed different mechanical properties, However, in both samples, there was a significant decrease (P <0.05) in all creep parameters except retardation time with increasing storage time. The effect of storage temperature on these parameters was also checked that results showed the reduction of these parameters in the non-technical storage especially in the Clone variety compared to the technical storage. A mathematical model showed as well the creep behavior of stored potatoes. Regression equations showed good results (R2 = 0.73-0.85) for the effect of storage time and temperature on creep parameters. The results of these equations showed that the Instantaneous modulus of elasticity parameter had the most effect on the creep parameters. According to these results, it can be said that in technical storage due to low temperature and controlled moisture than non-technical storage, there are better conditions for tuber durability than non-technical warehouse. The length of storage period of ‘Agria’ genotype is higher due to lower loss of moisture content and starch content and no sprouting compared to ‘Clone’ genotype. However, the tissue of the ‘Clone’ genotype is softened in comparison to the fresh sample less than two months in non-technical storage and less than three months in the technical storage due to the loss of moisture and the reduction of starch content that directly affected on tissue.