Qualitative and quantitative application of Fourier transform near-infrared (NIR) and attenuated total reflection mid-infrared (MIR) spectroscopy for the evaluation of pomegranate seed oil quality

Soaring demand for high-quality pomegranate seed oil because of the health benefits associated with its consumption has gained global attention. The assessment of quality characteristics associated with pomegranate oil is known to be expensive, labor intensive and impractical on a commercial scale. Alternative ways of assessing quality attributes of this co-product of pomegranate fruit that are rapid, easy, and cost-effective are being implemented to meet consumers’ satisfaction and production demand. This paper evaluates the application of rapid non-invasive methods, namely Fourier transform near-infrared (FT-NIR) and mid-infrared (FT-MIR) spectroscopy, to predict the quality attributes of pomegranate seed oil qualitatively and quantitatively. For qualitative analysis, MIR spectra provided reliable discrimination between oil samples from different cultivars when using principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). For quantitative analysis, partial least squares regression was used to construct models, and the results suggest that FT-NIR spectroscopy was able to predict the total carotenoid content (R², coefficient of determination, RMSEP; root mean square error of prediction, RPD; residual prediction deviation) (R²=84.38, RMSEP=0.019, RPD=2.28) and FT-MIR spectroscopy showed satisfactory prediction in peroxide value (R²=91.99, RMSEP=1.05, RPD=3.54) and refractive index (R²=91.27, RMSEP=0.0002, RPD=3.43). These results demonstrate the potential of infrared spectroscopy combined with chemometric analysis to rapidly screen pomegranate oil quality attributes.