Seeing structure, sensing softening: Decoding the microstructural mediation between optical properties and peach...

Area of Science:

• Agricultural Engineering
• Biophysics
• Food Science

Background:

• Nondestructive fruit quality assessment relies on understanding optical properties.
• Existing chemometric models lack mechanistic insights into spectral signal correlations.

Purpose of the Study:

• To decode the optical detection mechanism of peach firmness.
• To establish a quantitative "Optics-Structure-Mechanics" framework for peach firmness.
• To bridge the gap between spectral signals and biophysical mechanisms in fruit quality assessment.

Main Methods:

• Utilized spatial frequency domain imaging (SFDI) to measure peach optical properties (450-1040 nm).
• Quantified physiological attributes (SSC, MC, WSP, ASP) and microstructural features.
• Employed Cellpose-SAM deep learning for cellular segmentation and structural equation modeling for analysis.

Main Results:

• Identified 670 nm and 950 nm as key wavelengths for firmness prediction (R²=0.77 and 0.65).
• Cellular morphology was a dominant factor (46.77% contribution) in predicting firmness.
• Acid-soluble pectin (ASP) degradation and water-soluble pectin (WSP) accumulation modulated optical properties by affecting intercellular adhesion.

Conclusions:

• Established a quantitative mechanism linking peach optical properties, microstructure, and biochemistry to firmness.
• Demonstrated the dominant role of cellular morphology in optical firmness assessment.
• Provided a robust biophysical foundation for advanced optical quality assessment in fruits.