Rapid and non-destructive determination of rind biochemical properties of ‘Marsh’ grapefruit using visible to near-infrared spectroscopy and chemometrics

Rind biochemical properties play major roles in defense mechanism against the incidence of rind pitting during cold storage. At optimum concentrations, these properties could enhance fruit appearance and consumer acceptability. However, conventional methods of analysis are destructive and time-consuming. Consequently, a robust visible to near-infrared spectroscopy (Vis/NIRS) based non-destructive models coupled with chemometrics were developed to rapidly determine biochemical properties of ‘Marsh’ grapefruit rinds using FOSS NIRSystems to acquire spectral information from 400 to 2500 nm. Outliers were identified using principal component analysis and reference parameters were determined using conventional analytical methods. Pre-processing algorithms such as Savitzky-Golay was used to correct light scattering properties of the spectra and methods with best results in terms of higher coefficient of determination (R²), residual predictive deviation (RPD), lower root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) were used for model development. Rind biochemical properties of fruit were analyzed using Vis/NIRS and conventional methods before and after 9 weeks of cold storage, respectively. Results obtained using partial least square regression showed good to excellent prediction models for determining properties such as sucrose (R²=0.99, RMSEP=0.11, RPD=11.42), glucose (R²=0.99, RMSEP=0.77, RPD=11.35), fructose (R²=0.99, RMSEP=0.99, RPD=14.23), total phenolics (R²=0.94, RMSEP=0.07, RPD=3.85), total flavonoids (R²=0.99, RMSEP=0.07, RPD=12.37), vitamin C (R²=0.79, RMSEP=0.06, RPD=2.01), radical-scavenging activities (R²=0.91, RMSEP=0.17, RPD=3.07), chlorophylls a (R²=0.86, RMSEP=0.08, RPD=2.53) and b (R²=0.97, RMSEP=0.14, RPD=5.67). These results demonstrated the precision and robustness of models in determining rind biochemical properties of ‘Marsh’ grapefruit rapidly and non-destructively.