Main content area

Fourier transform near infrared diffuse reflectance spectroscopy and two spectral acquisition modes for evaluation of external and internal quality of intact pomegranate fruit

Arendse, Ebrahiema, Fawole, Olaniyi Amos, Magwaza, Lembe Samukelo, Nieuwoudt, Helene, Opara, Umezuruike Linus
Postharvest biology and technology 2018 v.138 pp. 91-98
anthocyanins, ascorbic acid, color, computer software, firmness, fruit quality, fruits, models, nondestructive methods, optical fibers, pH, phenolic compounds, pomegranates, prediction, reflectance spectroscopy, statistical analysis, titratable acidity, total soluble solids
Fourier transform near infrared (FT-NIR) diffuse reflectance spectroscopy as a non-destructive method for the development of calibration models has been investigated as a means of assessing the quality of whole pomegranate fruit. FT-NIR diffuse reflectance spectrometers with different spectral acquisition modes were evaluated using direct contact between the sample and the integrating sphere (IS), or by a contact-less measurement using an optic fibre coupled emission head (EH) to scan fruit over a distance of 170 mm. Fruit weight, firmness and colour components (a*, Chroma, hue angle), total soluble solids (TSS), pH, titratable acidity (TA), sugar to acid ratio (TSS:TA), BrimA, total phenolics, total anthocyanin and vitamin C. The best prediction statistics obtained from calibration models of the EH were firmness (R2 = 83.0, residual predictive deviation (RPD) = 2.43), fruit colour components (a*: R2 = 90.9, RPD = 3.34); Chroma: R2 = 83.0, RPD = 2.43, TSS (R2 = 78.1, RPD = 2.17), TA (R2 = 76.8, RPD = 2.12), BrimA (R2 = 76.2, RPD = 2.08), total phenolics (R2 = 88.0, RPD = 2.91) and vitamin C (R2 = 76.2, RPD = 2.06). The best prediction obtained from calibration models of IS were colour component Hue (R2 = 83.9, RPD = 2.50), TSS:TA (R2 = 86.8, RPD = 2.72) and total anthocyanin (R2 = 62.6, RPD = 1.64). Overall, good prediction was observed for both the EH and IS; however, better prediction performance was obtained with the EH which gave the best prediction for 9 of the 13 quality parameters evaluated. These findings have demonstrated that the EH (a contactless option of the Matrix-F) can be implemented as an online tool for the analysis of pomegranate fruit quality.