Study On Rheological Properties And Damage Control Of Hetao Muskmelons

The rheological study was conducted in order to solve the problem of damage during storage and transportation of Hetao muskmelon. The following conclusions were drawn from the experimental results :1) Strain-stress curves of the about spherical body of intact Hetao muskmelon fruit under quasi-static loading were developed under different loading rate and temperature conditions. The strain-stress curves indicate that the loading development lags behind that of the contact area of the sample at early compressing stage. The micro tissues of the fruits under compression at a smaller rate were more easily destroyed, which due to damage diffusion and enlarging the damage volume. The fruits compressed in vertical direction were more easily get to state of yield than that of compression in the horizontal direction, so, resulting in much serious damage degree.2) The five mechanical parameters were all significantly affected by the effective factors, such as stiffness of the fruits, temperature and loading. Statistic analysis indicated that yield force presented a significant positive correlation with deforming energy, and a least correlation between break force and yield force and yield energy.3) The textural properties may be nondestructively predicted and examined through the linear regression models developed of the effect of the mechanical parameters of Hetao muskmelon on the textural property indexes.4) The method was established to estimate the damage degree due to quasi-static loading quantitatively. The regression equations of the effective factors, such as the fruits'stiffness, loading rate, temperature and compressing direction, were developed to control and predict Hetao muskmelon's damage degree quantitatively under different storage and transportation conditions.5) The virtual prototyping technology on the ADAMS software platform was applied to set up a creep model of Hetao muskmelon under static loading. Both the constitutive equation and creep property parameters were obtained through running the simulated model. The change process of creep properties under different conditions was able to directly observed by running the ADAMS model6) Both constitutive equations and the parameters of creep properties of Hetao muskmelon were developed so as to lay the foundation for further study on rheological properties.7)Creep curves changed with the creep parameters, meanwhile, the effective factors, such as temperature, fruit'stiffness and loading, obviously affected the five creep property parameters. Thus, it is indicated that the creep behaviors of Hetao muskmelon obviously changed with the conditions of both storage and transportation and itself. It suggested that low temperature and less loading should be adapted in storage and transportation for the mature fruits. On the other hand, the way of slightly high temperature and less loading should be used for less mature fruits out of economical view.8)Exponential regression equations were set up to well express change of the creep property parameters with prolonging storage time. Moreover, linear regression models were established to reflect change of the textural property indexes, such as internal ethylene concentration, refractive sugar concentration, water content and total soluble solid concentration, in accordance with change of creep parameter during the period of storage. Statistic analysis showed that the above regression equations were meaningful and suitable to predict and examine nondestructively the quality and effective storage time of Hetao muskmelon.