Relationships between optical properties of peach flesh with firmness and tissue structure during storage

Abstract

Abstract The relationship between optical properties and tissue structure of firmness has been investigated. The light absorption (absorption coefficient, μa) and scattering properties (reduced scattering coefficient, μ’s) of ‘Baifeng’ and ‘Xiahui 8’ peaches were acquired using a single integrating sphere (SIS) system combined with an inversion algorithm over a 6 d period at 20 °C. The relationship of μa and μ’s with the firmness, equivalent diameter (dF), roundness (e), cell wall thickness (CWT) and intercellular space rate (Ris) were quantitatively analyzed at different wavelengths, and prediction models were established by partial least squares regression (PLSR). The results showed that firmness was correlated with structural parameters (except e), especially with Ris and CWT (r≥0.750). In addition, firmness, Ris and CWT had good correlations with optical scattering in melting ‘Baifeng’ peaches (r≥0.919). Similar results were also found for prediction models of firmness, CWT and Ris based on μ’s (Rp2≥0.799). Moreover, in nonmelting ‘Xiahui 8’ peaches, both firmness and CWT had good correlations with optical scattering (r≥0.976), which is consistent with the correlation analysis results of firmness and structural parameters. In addition, in the models based on μ’s for predicting firmness and CWT, Rp2≥0.823. These results further verified that the prediction of firmness based on optics may be related to the high correlation between tissue structural parameters and scattering properties.