Non-destructive determination of of soluble solids content in intact dovyalis (Dovyalis abyssinica Warb. xD. hebecarpa Warb.) fruit by means of NIR spectroscopy
Introduction: The Dovyalis is an exotic fruit originated in Africa, reddish-orange color, high acidity and soluble solids content (SSC). Doviális fruit is usually acid and used to juice production, however there are some hybrid that produce fruit high SSC which intended for consumption in nature. This study reports the rof Partial Least Squares Regression (PLSR) models developed using FTNIR reflectance spectra (1,000-2,500 nm) obtained from intact Dovyalis (Dovyalis abyssinica Warb. x D. hebecarpa Warb.)fruit to estimate SSC.
Materials and Methods: A total of 97 intact Dovyalis fruit were collected in 2015 season at collection orchard in Jaboticabal, SP, Brazil. Three spectra for each fruit were collected in the different side, totalizing 291 spectra, which were reduced the average. After temperature stabilization (~25C), the spectra were collected by using a FT-IR spectrophotometer (Spectrum 100N, PerkinElmer) in the diffuse reflectance mode over the range of 4,000-10,000 cm-1 (1,000-2500 nm, 64 scans, spectral resolution of 8 cm-1). Each PLSR model was constructed with 97 spectra which were divided calibration (c, n=60) and external validation (ev, n=37) set after and before pre-treat. The pre-processing was applied to spectra, namely standard normal variate (SNV) and first and second derivative of Savitzky-Golay.
Results and Discussion: The best PLSR model was obtained when the spectra were pre-processed using first derivative of Savitzky-Golay with 11 windows and elimination of 2 outlier which were detected by the Hoteling T2 (P<0.050) test. It was possible to get 6 latent variables (LV1 = 78 %) with a RMSE ev of 0.86 º Brix, the standard deviation from external validation set of 1.9 ºBrix, and a Rev2 of 0.80%. The PLSR model obtained using raw spectra showed 12 latent variables (LV1 = 20 %) with a RMSECev of 0.1,08% and a Rev2 of 0.74%. The The RPD is defined as the ratio of the standard deviation of the SSC from external validation set to the RMSEev from PLSR models had observed values of within the range of 1,8 to 2.3 indicating that this model was coarse quantitative predictions are possible for the SSC prediction in of intact Dovyalis fruit.
Conclusion: The PLSR model obtained with intact Dovyalis fruit after first derivative of Savitzky-Golay processing spectra presented better performance than the raw spectra. The NIR spectroscopy has shown to be a promising non-destructive method for the determination of soluble solids content in intact Dovyalis fruit to sort of fruit to in nature consumption.