Soft Mango Firmness Assessment Based on Rayleigh Waves Generated by a Laser-Induced Plasma Shock Wave Technique

Area of Science:

• Physics
• Agricultural Science
• Material Science

Background:

• Assessing fruit firmness is crucial for determining ripeness and quality.
• Traditional methods often involve destructive testing or lack precision for soft-fleshed fruits.
• Existing acoustic vibration methods, like the ₀S₂ mode, are ineffective for soft fruits like mangoes.

Purpose of the Study:

• To develop a non-contact, non-destructive method for assessing mango flesh firmness.
• To investigate the correlation between Rayleigh wave propagation velocity and mango firmness during ripening.
• To evaluate the feasibility of using laser-induced Rayleigh waves for fruit quality assessment.

Main Methods:

• Generating Rayleigh waves on mangoes using laser-induced plasma shock waves.
• Measuring Rayleigh wave propagation velocity along the fruit equator.
• Correlating wave velocity changes with fruit firmness, density, and Poisson's ratio over a 96-hour storage period.
• Analyzing the influence of the internal seed on wave propagation.

Main Results:

• Rayleigh wave propagation velocity decreased by over 4% in Kent mangoes within 96 hours.
• Wave propagation velocity showed independent changes along different measurement lines.
• The method demonstrated a strong correlation between wave velocity and fruit firmness, assuming minor density and Poisson's ratio variations.
• The study considered the interaction of the mango seed with the Rayleigh wave propagation.

Conclusions:

• Laser-induced Rayleigh wave propagation offers a promising non-contact and non-destructive technique for monitoring mango firmness and ripening.
• The method's reliability is influenced by the internal seed structure, requiring further investigation.
• This approach can be adapted for other soft-fleshed fruits, advancing quality assessment technologies.