Test of a light emitting diode fully integrated pre-prototype spectrometer for rapid evaluation of table tomato (Solanum lycopersicum L., Marinda F1) quality

The present research aims to evaluate the performance of an optical pre-prototype based on light emitting diode, (450-860 nm) to quantify table tomatoes' quality features in a rapid and non-destructive way (Solanum lycopersicum L., Marinda F1). A total of 200 samples were analysed. Calibration of the pure near infrared (NIR, 960-1650 nm) and visible/near infrared (VIS/NIR, 400-1000 nm) commercial spectrometers to estimate the main tomato quality parameters, i.e. moisture content (MC) and total soluble solids (TSS), was performed by using PLS regression. Since no substantial differences were highlighted between the two commercial devices, to reduce the complexity while keeping the performance of the model using the whole spectra (1647 variables for VIS/NIR), a cost-effective pre-prototype was designed and built by using 12 bands in the VIS/NIR optical range. The pre-prototype shows slightly lower performance, resulting in RMSEP values of 2% and 1.45 degrees Brix for MC and TSS respectively, compared to RMSEP values of 1% and 1.19 degrees Brix for the VIS/NIR device (using the entire spectrum). Moreover, no significant differences at 95% were highlighted by using Passing-Bablok regression. In conclusion, the pre-prototype performance can be considered sufficiently accurate to allow an initial field screening of the trend of the analysed parameters (MC and TSS) using a new generation of simplified optical sensors.