IN-VIVO MEASUREMENT OF TOMATO FIRMNESS

The objectives of the experiments were to investigate the firmness changes of tomato during growing and ripening, to examine the applicability of the widely used acoustic stiffness method during growing and ripening.
Samples of two greenhouse grown tomato varieties, Preciza and Boderine were examined.
The experiment lasted more than two months and all together 57 samples were examined in every 2-3 days.
The resonance frequency of the tomatoes showed a decreasing trend during development and ripening.
At the beginning of the process an asymptotic like change can be observed.
Significant frequency decrease was detected few days before the tomato reached harvest ripeness stage.
The volume changes during growing can be approximated by an exponential curve.
The density of the tomato increased from 975 kg m^-3 to 995 kg m^-3 during ripening.
According to the theoretical consideration
and the results of the finite element analysis, the S₂ = f²·m^2/3 and S₃ = f²·d² stiffness coefficients are able to describe the firmness changes during growing.
All the three investigated stiffness coefficients ( S₁ = f²·m, S₂ = f²·m^2/3 and S₃ = f²·d²) are able to follow the changes during ripening, so the S₂ and the S₃
were used to calculate the stiffness coefficient in this situation.
The tomatoes softened both during growing and ripening.
By reaching a certain maturity stage, the firmness of samples decreased significantly (at approx.
S₂ = 1·10⁷ Hz²g^2/3 or at approx.
S₃= 1700 m²s^-2). After this point the samples softened as much in the next 2-3 days as during 20-25 days before.

International Symposium on High Technology for Greenhouse System Management: Greensys2007

V. Zsom-Muha, T. Zsom, J. Felföldi

acoustic; stiffness; ripening; development

https://doi.org/10.17660/ActaHortic.2008.801.78