Research on the Biomechanical Characteristics of Salted Wakame (Undaria pinnatifida)

Abstract

At present, there has been no mechanized equipment designed for the separation of the leaves from the stems of wakame in China, and the stem–leaf separation is mainly completed by manual work, which suffers from problems such as low efficiency, high cost, and poor quality. To develop mechanized stem–leaf separation equipment of wakame, it is necessary to have a preliminary understanding of the biomechanical characteristics of wakame. In this study, we adopted an electronic universal testing machine, a texture tester, and a friction tester to investigate the mechanical characteristics of the stems and leaves of salted wakame. Analysis was performed to clarify the effects of salted wakame thickness and loading speed on the tension, compression, shear, and separation mechanical properties as well as the effects of the loading speed, normal force, and contact material on the friction characteristics. As shown in the results, the average tensile strength, shear strength, and resilience of salted wakame stems were 2.27 MPa, 6.34 MPa and 0.27, respectively; the average tensile strength and shear strength of salted wakame leaves were 1.67 MPa and 2.93 MPa; the separation strength of the stems and leaves was 1.78 MPa, and the friction coefficient between salted wakame and stainless steel, silicone rubber, and vulcanized rubber was 0.38, 0.44 and 0.40 on average. In general, the increase in the loading rate, the shear strength, and the stem–leaf separation strength of salted wakame showed a downward trend, while the changes in the friction coefficient showed an upward trend, with no significant influence on the recovery and tensile strength. The tensile strength, resilience, shear strength, stem–leaf separation force, and strength increased as the thickness of the salted wakame improved. The friction coefficient of the salted wakame stems decreased with increasing the normal force, while the friction coefficient of the salted wakame leaves increased. In general, the increase in wakame thickness improved its mechanical properties, and the increase in the test loading rate led to the decrease in the mechanical properties of salted wakame. The research results in this paper can provide suggestions for the research and development of stem–leave separation equipment for saline salted wakame.