Rapid and non-destructive measurement of spinach pigments content during storage using hyperspectral imaging with chemometrics

Hyperspectral imaging covering spectral range of 874-1734 nm was used to measure spinach leaf pigments content (chlorophyll-a (Chla), chlorophyll-b (Chlb), total chlorophyll (tChl), carotenoids (Car)) under storage of 20 °C (Sample set 1) and 4 °C (Sample set 2). A sample set combining the two sample sets was formed, partial least squares (PLS) models on full spectra obtained acceptable results for all sample sets with correlation coefficient of prediction (rp) near or over 0.8. Random frog was used to select 20, 20, 20, 22 optimal wavelengths for Chla, Chlb, tChl and Car from the combined sample set, respectively. PLS models on optimal wavelengths obtained better results than corresponding full spectra PLS models. The visualization of the distribution map of pigments content were acquired by applying the PLS models on pixels within the hyperspectral image. The overall results indicated that hyperspectral imaging could be used for spinach leaf pigments content measurement, providing an alternative for real-world on-line vegetables quality monitor.