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)