Nondestructive Characterization of Citrus Fruit by near-Infrared Diffuse Reflectance Spectroscopy (NIRDRS) with Principal Component Analysis (PCA) and Fisher Linear Discriminant Analysis (FLDA)

Abstract

The nondestructive characterization of citrus varieties (Egyptian sweet orange, Lane Late navel orange, Australian orange, and Blood orange) was developed based on near-infrared diffuse reflectance spectroscopy (NIRDRS) together with principal component analysis (PCA) and Fisher linear discriminant analysis (FLDA). An experiment for the penetration of NIRDRS into the peel was designed and the effects of different spectral acquisition points were investigated. Pretreatments were used to eliminate the spectral interferences. As an unsupervised pattern recognition method, PCA was used to establish the characterization models. Furthermore, supervised pattern recognition based on PCA and FLDA was employed to enhance the accuracy. The results of the penetration experiments show that near-infrared light enters the citrus peel and is able to characterize the internal composition. Even with the optimized spectral pretreatment, accurate characterization of citrus varieties was not achieved by PCA. However, the accurate characterization of citrus varieties was provided by PCA-FLDA. The accuracies of four spectral acquisition points are 95%, while the characterization accuracies of six spectral acquisition points are 100% combined with optimized spectral pretreatment. Therefore, NIRDRS with PCA-FLDA is suitable for the rapid and nondestructive characterization of citrus varieties.

Keywords:

• Fisher linear discriminant analysis (FLDA)
• near-infrared diffuse reflectance spectroscopy (NIRDRS)
• nondestructive analysis
• orange
• principal component analysis (PCA)

Disclosure statement

The authors declare that they have no conflicts of interest.

Additional information

Funding

This study was supported by National Natural Science Foundation of China (Number 31601551), China Postdoctoral Science Foundation (Number 2019M650187), and Project Supported by Scientific Research Fund of Hunan Provincial Education Department (Number 21A0127).