冬枣果实物理参数与生物特性研究

Study on the physical and biological properties of winter jujube fruit

为确定冬枣的机械选择性收获参数,试验测定不同成熟度果实的物理及生物特性参数,对其物理及生物特性参数之间的关系进行研究。结果表明:未熟期、白熟期和脆熟期的冬枣果实密度分别为902.15、911.68和947.06kg/m3,硬度分别为17.26、16.24和13.9kg/cm2,果实成熟度越高果实密度越大而果实硬度越小,脆熟期果实的密度及硬度与白熟期和未熟期果实的密度及硬度都存在显著性差异;未熟期、白熟期和脆熟期果实的树枝与果柄分离力都大于果实与果柄分离力,在机械振动收获时,果实脱落发生在果实与果柄连接处,分离力都随着成熟度的增加而减小,白熟期和脆熟期果实的果实与果柄分离力存在显著性差异,有望实现选择性收获;白熟期和脆熟期果实的压缩曲线趋势相似,都没有明显的生物屈服点。白熟期果实的破裂力为145.77N显著大于脆熟期果实的破裂力128.95N,果实和脆熟果实的压缩弹性模量均值分别为2.09和1.89 MPa,二者无显著性差异。果实破裂前,果实所受压力与变形呈近似线性关系。

Physical and biological properties of winter jujube in different maturity stages were studied in order to achieve mechanical selective harvesting.The results showed that：The density of winter jujube（902.15,911.68and947.06kg/m3）was increasing from under maturity to crisp maturity stage.The firmness（17.26,16.24 and 13.9kg/cm2）was decreasing from under maturity to crisp maturity stage.There were significant differences between density as well as hardness of crisp ripe fruits and that of white ripe and under ripe fruits.The detachment force between stem and branch is larger than that between fruit and stem,and both of them were decreasing as the fruit ripening.Therefore,the fruit detachment occurred at the location between stem and fruit under vibration harvesting.There was a significant difference in the detachment force of fruit and stalk between the white ripe fruits and the crisp ripe fruits,which indicated apossibility of selective mechanical harvesting.The compression curves of white ripe and crisp ripe fruits changed with a similar trend that both have not the bioyield point.The average maximum rupture force of white ripe fruits（145.77N）was significantly greater than that of the crisp ripe fruits（128.95N）.The elastic modulus of the white ripe fruits（2.09MPa）was slightly larger than that of the crisp ripe fruits（1.89MPa）.There was no significantly difference among elastic modulus.Before fruits rupture,linear function can be used to express the relationship between force and deformation.