Physical properties of guna fruits relevant in bulk handling and mechanical processing
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Department of Agricultural and Environmental Resources Engineering, University of Maiduguri, Maiduguri, Nigeria
Int. Agrophys. 2007, 21(1): 7–16
The physical properties of guna fruits, relevant in bulk handling and mechanical processing, were determined and the effect of variety, post harvest history and moisture content investigated. Two varieties of the crop, namely Citrullus colocynthis and Citrullus lanatus, three post harvest storage durations of eight weeks, four weeks and fresh state that gave three moisture levels in the ranges of 87.21-92.45% (w.b.) and 85.07-89.74% (w.b.) for the Citrullus colocynthis and Citrullus lanatus fruits, respectively, were used. Fruit moisture content was found to decrease with increase in storage period. In the above moisture ranges, the major and minor semi-axial dimensions varied from 5.27 to 5.71 cm and 5.18 to 5.61 cm, respectively, for the Colocynthis variety and from 4.53 to 4.96 cm and 4.25 to 4.66 cm, respectively, for the lanatus. The thickness of the epicarp and mesocarp and fruit volume, the fruit, pod and pulp masses, as well as the pod-fruit and pulp-fruit mass ratios increased with increase in moisture content for each fruit variety, while the average seed mass remained virtually constant and the seed-fruit mass ratio decreased with increase in moisture. The true and bulk densities of the fruits also increased with increase in moisture content and ranged from 0.767 to 0.803 g cm-3 and 0.664 to 0.698 g cm-3, respectively, for the colocynthis fruit, and from 0.637 to 0.765 g cm-3 and 0.554 to 0.665 g cm-3, respectively, for the lanatus. Regression equations that could be used to adequately express the relationship existing between the above properties and fruit moisture were established. The impact strength, bioyield, yield and rupture points and the bioyield, compressive and rupture strengths, as well as the modulus of stiffness and modulus of elasticity of the fruits were higher at the longitudinal loading orientation than at the lateral. At a similar storage condition, all the properties investigated were higher for the Citrullus colocynthis fruits than those of Citrullus lanatus.