Effects of Temperature and Loading Characteristics on Mechanical and Stress Relaxation Properties of Sea Buckthorn Berries. Part 2. Puncture Tests.

J. Khazaei, Danny D Mann

Abstract


Puncture force and energy were measured at different loading velocities and probe
diameters for two cultivars of sea buckthorn berries of various sizes at several ambient
temperatures. In addition to the puncture properties, the firmness-temperature coefficient,
the compression coefficient (Kc), shear coefficient (Ks), and the apparent modulus of
elasticity were determined. The tests showed that the Sinensis cultivar was generally firmer
than the Indian Summer cultivar. With an increase in the berry temperature, the puncture
force and energy decreased significantly. The sea buckthorn berry showed a negative
firmness-temperature coefficient (FT) which ranged between –0.362 and -0.627% per
degree. The puncture force and energy for the large berries of the Sinensis cultivar was
significantly higher than that for the small berries. With an increase in loading velocity
from 0.3 to 9 mm/s, the puncture force and energy increased significantly. Puncture force
and energy also increased as probe diameter increased. As expected, puncture force and
energy decreased as storage time increased to 14 d. The mean values obtained for Kc and Ks
ranged from –1.079 to -1.575 N/mm2 and from 0.657 to 0.817N/mm, respectively. The
apparent modulus of elasticity of the sea buckthorn berries ranged between 0.24 and 1.25
MPa.

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