Engineering properties of Roma tomato variety (Derica spp.)

Abstract

Tomato is a delicate vegetable whose quality and shelf life could be reduced by physical damage, mechanical handling, harvesting and transportation  operations. Its engineering properties are necessary in the modelling of micro and macro scale mechanics as well as the design of equipment/containers  for harvesting, processing, transportation, separating, packaging and material handling with respect to externally applied compression stresses. In this  study, the physical properties (dimensions, arithmetic mean diameter, equivalent mean diameter, geometric mean diameter, sphericity, aspect ratio,  surface area, density and coefficient of static friction on various geometric surfaces) and mechanical properties (mass, force, firmness, compressive force,  compression distance, resilience and hardness) were evaluated for Roma tomato variety (Derica spp.), commonly found in Nsukka, Nigeria. The  values for length, width and thickness were determined as 61.93 mm, 53.86 mm and 53.44 mm, respectively, while the arithmetic mean diameter,  equivalent mean diameter, geometric mean diameter, sphericity, aspect ratio, surface area and density were 59.84 mm, 58.60 mm, 59.76 mm, 1.05, 1.07,  11257.14 mm² and 0.001 g/mm^-3, respectively. The coefficient of static friction for tomato samples was highest on plastic (0.26), followed by wood (0.25)  and carton (0.23). It was observed that ripeness significantly affected tomato fruit firmness and hardness. Unripe tomato fruits were firmer than the half- ripe and ripe tomato fruits (2.39 N/mm² > 2.27 N/mm² > 2.26N/mm² ). The mean mass, compressive distance, compressive force, resilience and hardness  of the fruits were 3.23 kg, 22.16 mm, 31.72 N, 722.78 N mm and 0.001 N/mm² respectively.