Compression analysis of dehydrated agricultural products

The textural properties of apple, banana, carrot and potato were experiment ally determined by uniaxial compressive tests of cylindrical specimens at a constant deformation rate of 5mm/min. Compression tests were performed, fo llowing air drying, at various moisture contents ranging from 0.2 to 6 kg/k g db. The tests were performed using a universal texture testing machine an d simple mathematical equations were used to correlate-the maximum experime ntal stress and the corresponding strain to the moisture content. It was sh own that the maximum stress decreases as the moisture content decreases, un til a critical moisture content of 1.8 kg water/kg dry solids. Further remo val of water tends to increase the maximum stress. The maximum experimental strain was found to increase as water was removed. The stress-strain data of compression test were modelled using a simple mathematical model, contai ning parameters such as the maximum stress (sigma(max)), the maximum strain (epsilon(max)), the elastic parameter (E) and the viscoelastic exponent (p ). The effect of the moisture content on the compressive behavior of dried materials was introduced through its effect on the model parameters. The sh ift in compression behavior at 1.8 kg water/kg solids leads to the conclusi on that there is an important change of structure at this moisture content.