Physico-Mechanical Properties of Garlic (Allium sativum L.) Bulbs and Cloves for the Design of Planting and Post-Harvest Machinery

Abstract

Garlic, a widely cultivated bulb crop, poses persistent mechanisation challenges owing to the irregular geometry of its bulbs and cloves. The lack of reliable engineering data on the physical and mechanical properties of garlic bulbs and cloves has remained a major constraint in the design and development of efficient garlic planting and post-harvest processing machinery. Therefore, the present research systematically characterised the physical and mechanical properties of garlic that are essential for the design of efficient planting, clove separation, grading, handling and post-harvest processing equipment. Laboratory experiments were conducted using 100 randomly selected garlic bulbs and their corresponding cloves. Standard engineering methods were employed to determine moisture content, polar and equatorial diameters, thickness, geometric mean diameter, shape index, sphericity, bulk and true density, porosity, angle of repose and coefficient of static friction on plywood, glass and mild steel surfaces. The results revealed that the average polar diameter, equatorial diameter, thickness and geometric mean diameter of garlic bulbs were 45.76, 42.93, 40.73 and 43.08 mm, respectively, while the corresponding values for garlic cloves were 25.45, 10.99, 8.86 and 13.53 mm, respectively. The bulk densities were 529.33 kg/m³ for bulbs and 568.67 kg/m³ for cloves, while the corresponding porosities were 45.49% and 50.49%, respectively. The bulbs were highly spherical, with a sphericity of 0.99, whereas the cloves had an elongated and wedge-shaped appearance, with a shape index of 0.53. A marked difference in flow behaviour was observed: the bulbs had an angle of repose of 50.24°, compared with 34.34° for the cloves, and both types showed the greatest adherence to mild steel, with static friction coefficients of 0.41 for the bulbs and 0.34 for the cloves. The engineering properties generated in this study provide design data for the development and optimisation of garlic planting, clove separation, grading, conveying and storage systems. These findings may support agricultural engineers, researchers and equipment manufacturers in designing efficient garlic processing machinery, thereby improving mechanisation, reducing post-harvest losses and enhancing the overall productivity of garlic production.