Fruit detachment force of multiple varieties kiwifruit with different fruit-stem angles for designing universal robotic picking end-effector

•Fruit detachment force (FDF) generally decreased with fruit-stem angles (FSA)•The minimum FDF of ‘Qinmei’ and ‘Cuixiang’ were at FSA of 80°, while of other three varieties were 60°.•FSA should not be too small or too large to reduce the instability of FDF.•Compared to FSA of 160°, ‘Hayward’ and ‘Cuixiang’ had smaller FDF at FSA of 180°.•FSA should be less than or equal to 140° to avoid stem breakage for ‘Xuxiang’