STRESS RELAXATION CHARACTERISTICS OF WHEAT KERNELS AT DIFFERENT MOISTURE
Grzegorz Łysiak
Katedra Eksploatacji Maszyn Przemysłu Spożywczego, Uniwersytet Przyrodniczy w LublinieJawad AL Aridhee
Abstract
The study focuses on evaluation of the impact of moisture on the relaxation characteristics obtained through uniaxial compression of single wheat kernels. Polish soft wheat (c.v. Emika) at eight different moisture levels. i.e. 8, 10, 12, 14, 16, 18, 20, and 22% (wet basis) was used in the research. The experiments were made with the help of a Zwick Z020 universal machine. Individual wheat kernels were compressed with constant load value of 50 N between two flat plates. Relaxation time was equal to 300 seconds. Values of the relaxation decay parameter Y(t) were established for the determined relaxation time. Parameters k1 and k2 for the model presented by Peleg and Normand were also calculated. Compression work and deformation increased with the moisture rise from 5 to 25 mJ and 0.2 to 1.0 mm, respectively. An increase of kernels moisture caused the load at relaxation time as well as the decay parameter Y(t) to decrease. The values at 22% moisture were more than two times lower that corresponding 8% water level. Coefficients k1 and k2 decreased from 3.5 to 1.5, and from 53 to 13, respectively. A linear relation between the two model coefficients was observed. The impact of kernel moisture on the analyzed parameters was described in the form of regression equations.
Keywords:
wheat, moisture, relaxation, rheological characteristicsReferences
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Katedra Eksploatacji Maszyn Przemysłu Spożywczego, Uniwersytet Przyrodniczy w Lublinie
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