A research group of Professor Naoki Hosoya (Department of Mechanical and Functional Engineering, Faculty of Engineering) of Shibaura Institute of Technology has developed a method to evaluate the hardness of soft fruits in a non-contact and non-destructive manner in a joint research with Professor Ichiro Kajiwara of Hokkaido University Graduate School.It is possible to evaluate the hardness by the propagation velocity of the "Rayleigh wave" generated on the skin by the shock wave (LIP shock wave) generated by the laser-induced plasma.
The maturity of fruits has a correlation with hardness, and mechanical methods are effective for fruits whose color and aroma do not change.In the mechanical evaluation method, a contact-type device such as a hammer or a shaker is used to evaluate the maturity of the fruit, and its hardness is evaluated based on the shaking method (vibration response) of the fruit.
Conventionally, a method of evaluating hardness by measuring 0S2 mode (vibration that expands and contracts like a football) frequency on the equator of a fruit has been applied to hard fruits.A previous study by the research team allowed non-contact measurement of apple hardness by generating 0S2 mode vibrations with LIP shock waves to prevent fruit damage.However, since 0S2 mode vibration may not be excited in soft fruits such as mango, Rayleigh wave (a type of surface wave) was examined as a measurement target and the correlation with hardness was verified.
In the experiment, 20 Rayleigh waves generated by the LIP shock wave were measured non-contactly with a laser Doppler vibrometer using XNUMX Kent species of mango as a sample.It was experimentally clarified that the wave propagation velocity of Rayleigh wave decreases as the storage period of mango increases.This made it possible to evaluate the hardness in a non-contact, non-destructive manner by generating a Rayleigh wave on the pericarp with a LIP shock wave and observing its propagation velocity.
Paper information:[Foods] Soft Mango Firmness Assessment Based on Rayleigh Waves Generated by a Laser-Induced Plasma Shock Wave Technique
