33843

Prediction of soluble solids content and firmness in low chilling peach fruit ‘Aurora 1’ using near-infrared spectroscopy (NIR)

Paloma Nascimento 1 ; lívia carvalho 2 ; Luis Carlos Cunha Júnior 3 ; Fabíola Pereira 4 ; Gustavo Henrique de Almeida Teixeira 2
Favorite this paper

Introduction: Peach is a fruit species traditionally grown in temperate regions. However, this species is also cultivated in subtropical and tropical regions due to the development of low chilling cultivars and horticultural techniques. Regarding the cultivars, ‘Aurora-1’ requires low exposure to low temperatures in order to break the dormancy of its gems. This yellow flesh peach has around 14°Brix and as the soluble solids content (SSC) impacts highly on the consumer acceptance, SSC determination is an important quality attribute. NIR spectroscopy has been already used as an analytical method to predict SSC and firmness in intact peach fruit, but the models were developed with temperate peach cultivars and in different cultivation regions. Then, the objective of this study was to develop a non-destructive analytical method using NIR spectroscopy to predict both SSC and firmness in low chilling peach fruit ‘Aurora 1’.
Materials and Methods: A total of 430 intact peaches were harvested in 2013 in 3 maturity stages (immature, mature and ripe), these fruits were used to build the calibration and validation models using the classical Kernnard-Stone algorithm. In 2014, 109 fruit were harvest to be the prediction set (external validation). The NIR spectra were obtained on the equatorial region of the "background colour" and "blush colour" of each fruit in the wavelength band ranging from 4,000 to 10,000 cm-1, with 64 scans, and spectral resolution of 8 cm-1 using a FT-IR Spectrum 100N spectrometer PerkinElmer. After spectra acquisition, the firmness was determined using a penetrometer and the results were expressed in kgf.cm-2. The SSC was quantified using digital refractometer and was expressed in °Brix. The Unscrambler® X.3 software was used to develop the partial least squares (PLS) models.
Results and Discussion: The spectra taken on the "background colour" and "blush colour" were not different according to the PCA and all spectra were used to develop the PLS models. Using the models developed with the spectra of the fruit harvested in 2013 to predict the SSC and firmness of the spectra collected in 2014 (external validation), the best prediction result for SSC was obtained pre-treating the spectra with MSC (SEP=1.02°Brix, RP2=0.45). Firmness prediction was better predicted using the second derivative of Savitzky-Golay (SEP=1.14 kgf.cm-2, RP2=0.35).
Conclusion: The NIR spectroscopy can be used to predict SSC and firmness in intact ‘Aurora 1’ peach fruit. This technique can be used as a non-destructive method in quality control processes to monitor ‘Aurora 1’ peach quality.
Novelty statement: Robust prediction of SSC and firmness in intact low chilling peach fruit ‘Aurora 1’ by means of NIR spectroscopy has been demonstrated for the first time.
Summary: PLS models on NIR spectral data (4,000-10,000 cm-1) illustrated that this technique can be used as a non-destructive method to predict SSC and firmness in intact ‘Aurora 1’ peach fruit, and have a considerable potential for monitoring peach quality in grading lines.
Acknowledgements: CAPES and FAPESP (2008/51408-1).