Relationship between shelf-life and optical properties of 'Yuanhuang' pear in the region of 400-1150 nm

摘要

The main goals of this study are to investigate the potential of absorption coefficient for the prediction of water contents in 'Yuanhuang' pear and analyze the relationship between the shelf-life and bulk optical properties in the range of 900-1050 nm. An automated integrating sphere (AIS) system was used to measure the total reflectance, total transmittance of pear flesh tissues in visible-Near infrared (Vis-NIR) range. These two measurements were used to estimate the absorption coefficient μ_a and reduced scattering coefficient μ'_s of pear samples by using an inverse adding doubling (IAD) light propagation model. The detection accuracy of the AIS system was verified by using both liquid (Intralipid-20% as scatterer) and solid phantom (TiO_2 as scatterer, carbon black as absorber). The relative error of measurement of μ'_s of liquid phantom with four different concentration (0.5%,l%,1.5%,2%) at 632.8 nm, 751 nm, 833 nm are less than 10% except for 2% concentration at 833 nm, and the relative error of measurement μ_a and μ'_s of solid phantom at 525.4 nm, 632.1 nm, 710.3 nm and 780.1 nm are less than 5% except for the μ_a at 525.4 nm. A total of 140 samples were used to conduct the moisture measurement, and drying method was used. Predictive models for moisture content from μ_a data were constructed using partial least squares regression (PLSR). The coefficient of correlation of calibration set (R_c) and validation set (R_p) were 0.50 and 0.45 respectively. The relationship between the shelf-life and optical properties was analyzed by dividing pear samples into three categories according to the actual shelf-life, and calculating classification accuracy by using actual and calculated shelf-life grade.