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.

中文翻译：

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贮藏过程中桃肉光学特性与硬度及组织结构的关系

摘要 研究了光学特性与组织结构硬度之间的关系。使用单积分球 (SIS) 系统结合反演算法在 6 d 周期内获得了‘白凤’和‘夏惠 8’桃的光吸收（吸收系数，μa）和散射特性（折减散射系数，μ's）在 20°C。在不同波长下定量分析μa和μ's与硬度、当量直径（dF）、圆度（e）、细胞壁厚度（CWT）和细胞间隙率（Ris）的关系，并通过偏最小二乘法建立预测模型回归（PLSR）。结果表明，硬度与结构参数（e除外）相关，尤其是与Ris和CWT相关（r≥0.750）。此外，硬度、Ris 和 CWT 与融化'白凤'桃子的光学散射具有良好的相关性（r≥0.919）。基于 μ's (Rp2≥0.799) 的硬度、CWT 和 Ris 预测模型也发现了类似的结果。此外，在未融化的'夏惠8号'桃中，硬度和CWT均与光散射具有良好的相关性（r≥0.976），这与硬度和结构参数的相关性分析结果一致。此外，在基于 μ's 预测硬度和 CWT 的模型中，Rp2≥0.823。这些结果进一步验证了基于光学的硬度预测可能与组织结构参数和散射特性之间的高度相关性有关。此外，在未融化的'夏惠8号'桃中，硬度和CWT均与光散射具有良好的相关性（r≥0.976），这与硬度和结构参数的相关性分析结果一致。此外，在基于 μ's 预测硬度和 CWT 的模型中，Rp2≥0.823。这些结果进一步验证了基于光学的硬度预测可能与组织结构参数和散射特性之间的高度相关性有关。此外，在未融化的'夏惠8号'桃中，硬度和CWT均与光散射具有良好的相关性（r≥0.976），这与硬度和结构参数的相关性分析结果一致。此外，在基于 μ's 预测硬度和 CWT 的模型中，Rp2≥0.823。这些结果进一步验证了基于光学的硬度预测可能与组织结构参数和散射特性之间的高度相关性有关。