Impact of ripening spherical fruits on hard flat surface.
Rahardjo B., Tamtomo P., Handoyo R., Utami T. S.
Author Affiliation: Department of Food and Agricultural Engineering, Gadjah Mada University, Yogyakarta, Indonesia.
: unpaginated
Abstract : The maturity of fruits is commonly determined from their firmness. The common method to determine the fruit firmness is to give pressure on fruit surface using fingers. Impact force working on the fruit surface can be modelled as a viscoelastic sphere with parameters consisting of consistency, index of elasticity and damping coefficient. It seems that the impact parameters can be used to indicate the fruit maturity. Therefore the objectives of this study were to model the impact force of free falling of fruits using a viscoelastic model and to relate the impact parameters with the maturity using subjective evaluation. Samples used were fruits with shape similar to sphere or with curve surfaces (sapota, tomato, guava, avocado, mango and papaya). The fruits when ripen are accompanied by the softening their textures. The samples were free fallen on hard surface. The force was measured using dynamic force transducer. The impact parameters were found using curve fitting. The maturity of the samples was evaluated by well trained panellists. A computer program was developed to scan the impact force, to eliminate the zero data, to integrate and to calculate the impact velocity and the displacement and then to estimate the impact parameters. The results indicate that most of the impact parameters can be related to the maturity scores of the samples. The consistency and index of elasticity decrease when the samples ripen. However, the coefficient of damping differs. The damping coefficients of guava and tomato increase when the fruits ripe, while the damping coefficient of sapota, avocado and mango decrease. It is likely that the damping coefficient is dependent on the viscosity of the fruit liquid. The results indicated that the impact parameters can be related to the maturity index. It seems that the maturity of fruits can be determined by impact.