Objective  Longan shelling is the key process in longan deep processing. Aiming at the problems of low manual shelling efficiency, large mechanical shelling damage and poor pulp integrity, the flexible double roller shelling device was designed.

Method  The way of first breaking the shell and then using the flexible roll shelling was proposed to break the shell according to the physical and mechanical properties of typical longan fresh fruit. The critical components of the longan shelling machine including the breaking shell mechanism, the feeding pressure plate and the peeling roll were designed. The cutting depth of the shell breaking cutter and the gap between the shelling flexible rollers were adjustable. Taking Guangdong ‘Chuliang’ longan fresh fruit as the research object, orthogonal test analysis was carried out. Three parameters, incuding the roller gap, roller speed and shell break size, were selected as experimental factors. The success rate of shelling, the loss rate of shelling and the integrity coefficient of pulp were selected as indexes to perform optimization test.

Result  The convenient and adjustable gap between rollers could meet the shelling processing of longan after classification, and the shelling device had good adaptability to longan with different fruit sizes. The roll gap had a significant effect on shelling performance. With the increase of roller gap from 3 mm to 5 mm, the integrity of longan pulp after shelling became worse, and the loss rate increased from about 7% to 18%. The ranking of influence was roller gap > roller speed > shell break size. When the roller gap was 3 mm, the rotation speed was 13.5 r/min and the shell break size was approximately 90°, the machine got the best shucking effect.

Conclusion  This study provides a reference for further processing of lantern shaped pulp obtained by mechanical shelling of longan and other flexible fruits and the parameter optimization of shelling machine.