Non-destructive assessment of quality parameters in 'Friar' plums during low temperature storage using visible/near infrared spectroscopy

In the present study, visible/near infrared (Vis/NIR) spectroscopy was used as a non-destructive method to predict the 'Friar' plum's quality parameters; soluble solids content (SSC), titratable acidity (TA), pH, firmness, sugar-acid ratio (SSC/TA) and flesh color (L*, a*, b*). Correlation coefficients were used to select the characteristic spectral regions using partial least squares (PLS) regression. A Pearson correlation analysis and principal component analysis (PCA) were used to explore the interaction between the parameters during low-temperature storage. The parameters' factor weightings were calculated using PCA to build a comprehensive PLS model for further assessment. The success of the prediction varied with the quality parameters: SSC (R-p(2) = 0.9456, RMSEP = 0.456 degrees Brix, RPD = 4.43), TA (R-p(2), = 0.7702, RMSEP = 0.0183%, RPD = 2.18), firmness (R-p(2), = 0.8250, RMSEP = 0.532 kgf cm(-2), RPD = 2.37), pH (R-p(2) = 0.8299, RMSEP = 0.1010, RPD = 238), SSC/TA (RI, = 0.7663, RMSEP = 15.6, RPD = 2.10), L* = 0.8673, RMSEP = 3.02, RPD = 2.68), a* (R-p(2)=0.6490, RMSEP = 2.52, RPD = 1.62) and b* (R-p(2)= 0.9252, RMSEP = 2.53, RPD = 3.19). In particular, flesh color proved to be an important factor to consider when assessing the quality of post-ripening during low-temperature storage. The satisfactory comprehensive PLS model provided good prediction results (R-p(2) = 0.8212, RMSEP = 38.9, RPD = 2.40) to enable a fair and reliable assessment of stored plums. (C) 2016 Elsevier Ltd. All rights reserved.