S. R. Karimi Akandi - Biosystems Engineering Department, Faculty of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.
S. Minaee - Biosystems Engineering Department, Faculty of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.
T. Tavakoli Hashjin - Biosystems Engineering Department, Faculty of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.
G. Najafi - Biosystems Engineering Department, Faculty of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.
S. Sh. Ghodsi - Biosystems Engineering Department, Faculty of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.

Compressive and shear properties of Aloe Vera leaves were investigated for gel extraction. This information is useful in the design of processing equipment and improving gel production lines in order to decrease losses and enhance product quality. Effects of loading speed (۱۰, ۵۰, and ۱۰۰ mm min-۱), temperature (۲۰, ۴۰, and ۶۰˚C), and diameter of the cylindrical loading head (۷۰, ۱۴۰, and ۲۱۰ mm) on the leaf compression properties, as well as the effect of loading speed on the shear properties were examined. The results showed that increasing the temperature would decrease the modulus of elasticity. Loading head diameters had a significant effect on the required force for crushing the leaves and extracting the gel. Based on the results, the best loading combination for extracting Aloe Vera gel from the leaf is ۲۰˚C temperature, loading head diameter of ۱۴ cm, and loading speed of ۱۰۰ mm min-۱. Shear forces of upper and lower leaf surfaces increased with loading speed. However, speed of loading had no effect on the shear forces at the edges and center of the leaf. The shear force was similar at different speeds for edge and center regions as well as for upper and lower surfaces of the leaf. Two gel extraction machines were developed based on the shear and compression properties of Aloe Vera leaves.

Compression test, Modulus of elasticity, Processing equipment, Shear test