Construction and evaluation of a low cost NIR-spectrometer for the determination of mango quality parameters

The perishable nature of agricultural produce (e.g. fresh fruits and vegetables) necessitates good decision making to avoid losses and maximize profits. Near infrared (NIR) spectroscopy is one of the tools that has proven useful for this purpose. However, despite the recent development of fairly low-cost portable instruments (e.g. SCiO, Linksquare, Neospectra), financially accessible NIR solutions still need to be provided for the technique to become more widely available. Therefore, herein we report the development of a prototype of a low cost NIR device based on the Hamamatsu C14384MA-01 minispectrometer. The spectrometer was equipped with both filament and LED light sources. The constructed device was used to collect NIR spectroscopic information from Nam Dok Mai mangoes and this data was used to develop predictive models for the quality parameters of mangoes: dry matter (DM), total soluble solids (TSS), titratable acidity (TA), pH, and firmness. Mango samples used for developing the predictive models were collected at two different time periods. The models were made using partial least squares regression (PLSR) and the data analysis used both unprocessed data and preprocessed data (e.g. Savitzky-Golay derivative, standard normal variate (SNV) normalization). The best models were developed for TA, pH, and TSS. The model for TA had values of R_c^2 and R_cv^2 of 0.82 and 0.84, respectively, while the RMSEC and RMSECV were 0.37 and 0.36