Abstract As Satsuma mandarin is a multi-layered fruit, the optical properties of the different tissue layers influence the performance of spectroscopy-based quality detection models. Therefore, the variation in the bulk optical properties (BOP) of the inner (juice vesicles) and outer (flavedo) tissue layer of Satsuma mandarin was investigated for different harvest times, fruit sizes and cultivars. Satsuma mandarin fruit from three different cultivars (Iwasaki, Okitsu and Goku Wase) were harvested at three different times around the recommended harvest date and the BOP of the inner and outer tissue layers were estimated from double integrating spheres measurements. Along the harvest time, the absorption peak related to carotenoids in the bulk absorption coefficient (μa) spectrum increased in both tissue layers, while the values attributed to chlorophylls decreased in the flavedo. Moreover, a slightly increasing trend over the harvest time was observed in the bulk scattering coefficient (μs) spectra of juice vesicles, especially at the early stage. The μa values of both tissue layers and the μs values of juice vesicles deviated among different fruit sizes, which can be related to the development stage. Smaller fruit presented a higher carotenoids concentration in juice vesicles, an advanced color change in flavedo throughout the maturation stages and higher μs values in juice vesicles at earlier maturation stages. The μa differences in pigment absorption among different cultivars were related to the maturation order. Earlier maturing cultivars possessed higher μa values related to carotenoids absorption in juice vesicles and advanced color changes in flavedo. The μs values of the flavedo differed among the cultivars and these differences were enhanced during maturation. These insights in the sources of variation in the bulk optical properties of Satsuma mandarin tissues can be used for simulation-based optimal design of an optical measurement configuration and interpretation of the acquired signals in spectroscopy-based quality detection and monitoring.

中文翻译：

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采收时间、果实大小和品种对蜜柑整体光学特性的影响

摘要 由于萨摩柑是一种多层水果，不同组织层的光学特性会影响基于光谱的质量检测模型的性能。因此，研究了不同收获时间、果实大小和品种的萨摩橘子内部（汁泡）和外部（flavedo）组织层的整体光学特性 (BOP) 的变化。来自三个不同品种（岩崎、Okitsu 和 Goku Wase）的萨摩柑橘在推荐的收获日期前后的三个不同时间收获，内部和外部组织层的 BOP 是通过双积分球测量估算的。随着收获时间，体吸收系数 (μa) 光谱中与类胡萝卜素相关的吸收峰在两个组织层中都增加，而归因于叶绿素的值在 flavedo 中下降。此外，在汁囊泡的体散射系数 (μs) 光谱中观察到随着收获时间略有增加的趋势，尤其是在早期阶段。两个组织层的μa 值和汁泡的μs 值在不同果实大小之间存在偏差，这可能与发育阶段有关。较小的水果在汁泡中表现出较高的类胡萝卜素浓度，在整个成熟阶段的 flavedo 颜色变化较大，在早期成熟阶段汁泡中的 μs 值较高。不同品种间色素吸收的μa差异与成熟顺序有关。较早成熟的品种具有较高的 μa 值，这与汁泡中类胡萝卜素的吸收和 flavedo 中的高级颜色变化有关。flavedo 的 μs 值在不同品种之间有所不同，并且这些差异在成熟过程中有所增强。这些对萨摩柑橘组织整体光学特性变化来源的见解可用于光学测量配置的基于模拟的优化设计，以及在基于光谱的质量检测和监测中对采集信号的解释。