Some Physical and Mechanical Properties of Kiwifruit

Abstract

In this paper, the physical properties such as length, width, thickness, geometric mean diameter, arithmetic mean diameter, mass, true volume, apparent volume, true density, bulk density, porosity, sphericity, surface area, shell ratio, aspect ratio, static coefficient of friction and mechanical characteristics namely firmness, hardness, adhesiveness, adhesive force and total positive area in puncture test were determined for kiwifruit of the Hayward variety. These properties are necessary in the design of the equipment for harvesting, processing and transportation, separating and packing. The results showed that the length, width, thickness, arithmetic mean diameter, geometric mean diameter, sphericity and aspect ratio of kiwifruit varied from 55.5 to 82.3 mm, 46.8 to 54.8 mm, 41.5 to 52.4 mm, 49.8 to 60.99 mm, 49.56 to 59.28 mm, 71.95 to 90.48% and 62.67 to 89.20%, respectively. While the surface area determined by McCabe et al.'s and Jean & Ball's formula, and surface area measured by experimental method changed from 77.11 to 110.34 cm2, 48.74 to 95.95 cm2 and 83.29 to 108.71 cm2, respectively. The values of the fruit's true volume, apparent volume, true density, bulk density and porosity were between 85-120 cm3, 63.69-109.01 cm3, 940-1040 kg/m3, 544.73-572.17 kg/m3 and 39.70-45.5%, respectively. Furthermore, the unit mass and peel ratio of kiwifruits ranged from 75.18 to 135.32 g and 8.91 to 12.51%, respectively. On four different surfaces, namely plywood, galvanized iron sheet, glass and fiberglass, static coefficient of friction varied from 0.34 on glass to 0.49 against plywood. The average firmness, hardness, adhesiveness, adhesive force and total positive area of peeled fruits were 229.42 g, 367.49 g, 716.48 g.s, -34.2 g and 11933.5 g.s, respectively. Corresponding values for unpeeled samples obtained 403.38 g, 2081.2 g, -3175.32 g.s, -118 g and 35757.22 g.s, respectively.