Flexible Shelling of Camellia Oleifera Fruits Based on Cracking Treatment: Key Components Design and Mechanism

Most existing Camellia oleifera fruits (COF) shelling machines were designed utilizing rigid components, leading to a high seed-breakage rate (SBR) and difficulty in seed-shell separation. In this paper, a new mechanical shelling method was developed based on low-temperature air-drying pretreatment coupled with a flexible shelling machine. Through kinetic analysis of the shelling process and critical stress analysis of crack extension of COF, the effects of the flexible shelling component on hitting force and collision contact time were studied, and the key parameters affecting shelling effectiveness were identified. The key shelling components were designed based on theoretical calculation and engineering experience. The response surface optimization tests of key shelling parameters were carried out, with roller speed, shelling gap, and air-drying time as test factors, SBR and shelling rate (SR) serving as performance metrics. The results revealed that utilizing the flexible shelling component can effectively extend collision contact time and reduce hitting force (by 138.1 N), thus reducing impact damage to Camellia seeds. The optimal combination of key shelling parameters was roller speed 250 r min⁻¹, shelling gap 16.8 mm, and air-drying time 2.5 h. Verification tests achieved a 98.7% SR, a 0.02% SBR, and showed that approximately 71.1% of Camellia shells remained complete with no juice leakage, facilitating subsequent sorting. The research results provided technical references for improving COF shelling machines.