Investigation of absorption and scattering characteristics of kiwifruit tissue using a single integrating sphere system

Journal of Zhejiang University-SCIENCE B, Jun 2016

For a quantitative understanding of light interaction with fruit tissue, it is critical to obtain two fundamental parameters: the absorption coefficient and the scattering coefficient of the tissue. This study was to investigate the optical properties of kiwifruit tissue at the wavelength of 632.8 nm. The total reflectance and total transmittance of kiwifruit tissue from three parts (including the flesh part, the seed part, and the seed-base part) were measured using a single integrating sphere system. Based on the measured spectral signals, the absorption coefficient μa and the reduced scattering coefficient μs′ of kiwifruit tissue were calculated using the inverse adding-doubling (IAD) method. Phantoms made from Intralipid 20% and India ink as well as a Biomimic solid phantom were used for system validation. The mean values of μa and μs′ of different parts of the kiwifruit were 0.031–0.308 mm−1 and 0.120–0.946 mm−1, respectively. The results showed significant differences among the μa and μs′ of the three parts of the kiwifruit. The results of this study confirmed the importance of studying the optical properties for a quantitative understanding of light interaction with fruit tissue. Further investigation of fruit optical properties will be extended to a broader spectral region and different kinds of fruits.

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Investigation of absorption and scattering characteristics of kiwifruit tissue using a single integrating sphere system

J Zhejiang Univ-Sci B (Biomed & Biotechnol) 1673-1581 Investigation of absorption and scattering characteristics of Zhen-huan FANG 0 Xia-ping FU 0 Xue-ming HE 0 0 (College of Biosystems Engineering and Food Science, Zhejiang University , Hangzhou 310058 , China) 1 Project supported by the National Natural Science Foundation of China (No. 31401289), the Zhejiang Provincial Natural Science Foundation of China (No. LQ12C10001), and the Education Department of Zhejiang Province (No. Y201122219) , China ORCID: Xia-ping FU For a quantitative understanding of light interaction with fruit tissue, it is critical to obtain two fundamental parameters: the absorption coefficient and the scattering coefficient of the tissue. This study was to investigate the optical properties of kiwifruit tissue at the wavelength of 632.8 nm. The total reflectance and total transmittance of kiwifruit tissue from three parts (including the flesh part, the seed part, and the seed-base part) were measured using a single integrating sphere system. Based on the measured spectral signals, the absorption coefficient μa and the reduced scattering coefficient μs' of kiwifruit tissue were calculated using the inverse adding-doubling (IAD) method. Phantoms made from Intralipid 20% and India ink as well as a Biomimic solid phantom were used for system validation. The mean values of μa and μs' of different parts of the kiwifruit were 0.031-0.308 mm−1 and 0.120-0.946 mm−1, respectively. The results showed significant differences among the μa and μs' of the three parts of the kiwifruit. The results of this study confirmed the importance of studying the optical properties for a quantitative understanding of light interaction with fruit tissue. Further investigation of fruit optical properties will be extended to a broader spectral region and different kinds of fruits. Optical properties; Integrating sphere; Inverse adding-doubling; Kiwifruit http; //dx; doi; org/10; 1631/jzus; B1500086 CLC number; S123 1 Introduction Visible-near infrared (Vis-NIR) spectroscopy has been widely applied for nondestructive assessment of the physical and chemical quality parameters of fruits by many research groups as well as companies. In conventional Vis-NIR spectral analysis, the spectra are always described by the absorbance of light based on Beer-Lambert Law (or Beer’s Law). The concentration of the compounds is proportional to the absorbance (Chen and Wang, 2001) . Quality assessments are typically executed based on large datasets using chemometrical methods. In this way, scattering is weakened or neglected, as well as are the complex light propagations inside the fruits. However, as a kind of turbid biological material, the constituents and structures of fruit tissue are very complex. Information about the interaction between light and fruit tissue is essential in the evaluation of fruit qualities, since optical signals are significantly affected by constituents and the physical structure of tissue. In light penetration in multiple scattering media, such as fruit, both scattering and absorption contribute to the distance-dependent attenuation. For a quantitative understanding of light interaction with fruit tissue, it is critical to obtain two fundamental optical properties characterized by the absorption coefficient (μa) and the scattering coefficient (μs) (Tuchin, 2007) . The measured absorption and scattering coefficients can be used not only for characterizing the absorption and scattering features, respectively, of fruit and vegetable tissues, but also for such investigations and applications as simulating light propagation inside tissues, assessing qualities of fruits and vegetables, and providing guides for their process optimization. Most studies measured the reduced scattering coefficient (μs') instead of μs. The relationship between μs' and μs is μs'=(1−g)μs, where g is the anisotropy factor. In biomedical engineering research, different methods have been used to measure absorption and scattering properties of different types of biological tissue (Cheong et al., 1990; Tuchin, 2007) . More information about the tissue is obtained because absorption and scattering properties are distinguished. All these methods can be classified into direct and indirect methods according to the theory and technique based on the study of Kim and Wilson (2011). Because of the critical experimental conditions that direct methods need, most methods reported are indirect methods (Tuchin, 2007) . Inverse adding-doubling (IAD) is one of the indirect methods based on addingdoubling theory. It usually uses an integrating spherebased system to measure the transmittance and reflectance of the tissue. Then, the optical properties of the measured tissue can be calculated in the inverse form of adding-doubling (Pickering et al., 1993; Prahl et al., 1993; Prahl, 2011) . Compared with other commonly used methods such as the time-resolved method, the spatially-resolved metho (...truncated)


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Zhen-huan Fang, Xia-ping Fu, Xue-ming He. Investigation of absorption and scattering characteristics of kiwifruit tissue using a single integrating sphere system, Journal of Zhejiang University-SCIENCE B, 2016, pp. 484-492, Volume 17, Issue 6, DOI: 10.1631/jzus.B1500086