Experimental research on the mechanical properties of Camellia oleifera fruit shell breaking by cutting and compression

To mitigate the damage rate of Camellia oleifera seeds during the process of Camellia oleifera fruit dehulling, a Camellia oleifera fruit cutting and compression machine was developed. This machine operates on the principle that the shell-breaking stress of Camellia oleifera fruit is reduced following cutting, thereby integrating the steps of grading, cutting, compressing, and separating for the dehulling of Camellia oleifera fruit. Utilizing the electronic universal testing machine, a 4-factor single-factor test was conducted, including the number of cutting knives, cutting direction, compressing direction, and Camellia oleifera fruit size. The results showed that the average breaking force of Camellia oleifera seeds was 196.33 N. Compared with direct separating without cutting, the shell-breaking of Camellia oleifera fruit with 1, 2, 3, and 4 cuts decreased 30.14%, 38.62%, 45.05%, and 47.74%, respectively. Compared with cutting along the long axis, the shell-breaking force of Camellia oleifera fruit cutting along the minor axis decreased 8.1%; however, the effect of cutting direction on shell-breaking force is not significant. The shell-breaking force of Camellia oleifera fruit compressing along the long axis was 24.11% lower than that of Camellia oleifera fruit compressed along the minor axis. With the increase of Camellia oleifera fruit size, the shell-breaking force of Camellia oleifera fruit also increased. The shell-breaking force of 25-30 mm, 30-35 mm, and 35-40 mm was 85.62%, 127.34%, and 178.69% higher than that of 20-25 mm, respectively. In conclusion, using grading measures, making one cut along the long axis and compressing along the long axis is a suitable method for husking of Camellia oleifera fruit.