The use of QuaSpec one-fiber spectrometer as non-invasive technology for leaf pigment estimation and its relation to post-harvest product quality

MSc-thesis abstract (submitted 26 June 2017): A preliminary study on QuaSpec one-fiber spectrometer was conducted in post-harvest of cut-roses and lettuce. The study aimed to test whether the device can measure absolute level of leaf chlorophyll and carotenoid providing future practical applications.
Besides non-invasive measurements (QuaSpec), a destructive technique was used as a benchmark. Spectra of pure leaf pigment molecules embedded in a lipid matrix were used to provide the mathematical model with essential spectra information. Furthermore, leaf pigment changes ratios were investigated as possible marker of senescence and quality in cut-rose vase life and storage of lettuce.

Destructive results showed that pigment changes did not occur in leaves during vase life of cut-roses tested in this research. Therefore, pigment ratios cannot be used as marker of flower senescence and quality in cut-roses.
Chlorophyll a/b ratio (Chl a/b ratio) was not leaf senescence and quality marker in storage of lettuce. However, chlorophyll/carotenoid ratio (Chl/Car ratio) and Chlorophyll a/carotenoids ratio (Chl a/Car ratio) resulted to be a leaf senescence and quality marker in storage of lettuce (Lactuca sativa L.).
Leaf total chlorophyll and overall visual quality (OVQ) showed strong correlation during storage of lettuce. QuaSpec was capable of measuring total amount of chlorophyll (concentration range from 23 to 8 μg/cm2).

QuaSpec could not measure Chlorophyll a (Chl a), Chlorophyll b (Chl b) separately and carotenoids (Car).
The mathematical model did not fitted properly the single fiber reflectance (SFR) spectra measured and absorption spectra deducted by dissolving pure leaf pigment molecules in vegetable oil. The fitted region of the spectrum was from 550 to 850 nm.
However, QuaSpec spectroscopic concentration resulted to be strongly correlated to overall visual quality (OVQ) during the whole storage period resulting in a possible application of the device for quality estimation of lettuce.