Effects of Temperature and Loading Characteristics on Mechanical and Stress-Relaxation Behavior of Sea Buckthorn Berries. Part 3. Relaxation Behavior

Relaxation force properties of single sea buckthorn berries under uni-axial compression were studied. Sea buckthorn berries had a time dependent behavior similar to other viscoelastic materials. The three-term Maxwell model with a maximum relative difference (MRD) of % 5 ≤ was chosen as the best fit equation to the relaxation data. For both Indian Summer and Sinensis cultivars, the firmness (as evidenced by the decay forces) decreased with temperature. As berry temperature increased from 4.5 to 34.5°C, F1 decreased 32.9 and 19.9% for the Indian Summer and Sinensis cultivars, respectively. Sinensis berries were significantly firmer than Indian Summer berries. For each cultivar, a master curve was proposed to determine the relaxation data of the sea buckthorn berries at temperatures between 4.5 and 34.5°C. Deformation level and loading velocity had a decreasing effect on relaxation time, but temperature had an increasing effect.