Optical properties of pig subcutaneous adipose tissuewere estimated using double integrating sphere (DIS)measurements
in combination with an inverse adding doubling (IAD) light propagation model. Total reflectance, total transmittance and unscattered transmittance were measured for the wavelength range 1150–2250 nm with 10 nm resolution. These measurements were used to estimate the bulk optical properties (absorption coefficient, scattering coefficient and anisotropy factor) of 10 Iberian pig adipose tissue samples. The estimated absorption coefficient spectra were dominated by water and lipid absorption bands, the main chemical components of the adipose tissue. These values showed a suitable match with the theoretical values calculated based on the average composition of the tissue. The obtained scattering coefficient spectra showed a smooth decrease with increasingwavelength,which is typical for biological tissues. The anisotropy factor spectra of adipose tissue were obtained, which describe the angular scattering pattern, instead of using a fixed value for the estimation
procedure. The optical characterization described in this paper is crucial for a better understanding of the impact of pure absorption and scattering on the NIR spectra collected by a single measurement in the laboratory, process line at the slaughterhouse or on the farm.Moreover, the estimated data reported in this study would promote a more efficient sensor design and data processing optimization.
Industrial relevance: This paper provides an optical characterization (absorption, scattering and angular scattering distribution) of pig adipose tissues in a wide near-infrared wavelength range (1150–2250 nm) based on a
novel spectroscopic setup. The estimated data reported are relevant to promote the design of innovative NIRS sensors and the development of new modeling procedures in order to optimize the non-destructive analysis of intact adipose tissues. This can have an important impact on the implementation of NIRS quality control systems in the agro-industry.