Rapid, simultaneous, and in situ authentication and quality assessment of intact bell peppers using near-infrared spectroscopy technology

Abstract

BACKGROUND: The ability of near infrared (NIR) spectroscopy to authenticate individual bell peppers as a function of the growing system (outdoor or greenhouse) was tested using partial least squares discriminant analysis (PLS-DA). 394 bell peppers grown outdoors (130 samples) or in a greenhouse (264 samples) during the 2015 and 2016 seasons, were selected for this purpose and analysed using a portable, handheld MicroPhazir MEMS instrument (spectral range 1600-2400 nm), working in reflectance. Subsequently, the potential of NIRS as a non-destructive sensor for in-situ quality (dry matter and soluble solid content) measurements, was investigated.

RESULTS: The models correctly classified 89.73% and 88.00% of the samples by growing system, when trained with unbalanced and balanced sets, respectively, mainly due to the differences in physical-chemical attributes between bell peppers cultivated in both growing systems. Separate classification models for bell peppers grouped by ripeness (judged by the colour), allowed to classify 88.28%-91.37% of the samples correctly. The standard error of cross-validation (SECV) values for the quantitative models were 0.66% fw and 0.75 ºBrix for dry matter and soluble solid content, respectively.

CONCLUSIONS: The results showed that NIRS can be used successfully for predicting the growing systems used in bell pepper production, which is of particular value to guarantee the authentication of outdoor-grown peppers. Additionally, the results showed that NIRS can be used simultaneously as a rapid preliminary screening technique to measure quality.