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- A TSS classification study of 'Rocha' pear (Pyrus communis L.) based on non-invasive visible/near infra-red reflectance spectraPublication . Bexiga, Florentino; Rodrigues, Daniela; Guerra, Rui Manuel Farinha das Neves; Brazio, António; Balegas, Tiago; Cavaco, A. M.; Antunes, Maria Dulce; Valente de Oliveira, JOSÉThe study focuses on the application of machine learning techniques for classifying the internal quality of 'Rocha' Pear (Pyrus communis L.), i.e., the total soluble solids (TSS), using the non-invasive technique of visible/near infra-red reflectance spectroscopy. Six representative classifiers were evaluated under realistic experimental conditions. The classifiers include representatives of classic parametric (logistic and multiple linear regression), non-parametric distance based methods (K-nearest neighbors), correlation-based (partial least squares), ensemble methods (random forests) and maximum margin classifiers (support vector machines). The classifiers were assessed against metrics such as accuracy, Cohen's Kappa, F-Measure, and the area under the precision recall curve (AUC) in a 10 x 10-fold cross-validation plan. For result analysis non-parametric statistical test of hypotheses were employed. A total of 4880 fruit samples from different origins, maturation states, and harvest years were considered. The main conclusion is that the maximum margin classifier outperforms all the others studied ones, including the commonly used partial least squares. The conclusion holds for both a reflectance spectrum with 1024 features and for a 128 subsample of these. An estimate of the out-of-sample performance for the best classifier is also provided.
- Quality changes during storage of apricot (prunus armeniaca l.) cv. ‘beliana’ and ‘lindo’ trated with calciumPublication . Antunes, Maria Dulce; Miguel, Maria Graça; Neves, M. A.; Cavaco, A. M.; Nunes, CarlaCalcium salts have been successfully used to maintain firmness and to slow down ripening processes in some fruit. This work studies the effect of postharvest calcium chloride applications on the quality preservation of apricot (Prunus armeniaca L.) cv. ‘Beliana’ and cv. ‘Lindo’ during storage. Harvested apricots were dipped in 0, 1, 3 or 5% CaCl2 solutions for 2 min. Fruit were left to dry for 1 h at ambient temperatures and then stored at 3 ºC. Fruit were analysed after 0, 6, 14, 21 and 28 d storage for weight loss, firmness and soluble solids content (SSC). A taste panel was performed at the beginning and at the end of the experiment. Weight loss increased through storage in both cultivars. ‘Lindo’ did not show differences among treatments in weight loss, but ‘Beliana’ had higher weight loss in fruit treated with 3% CaCl2 followed by 5%. Firmness decreased through storage without differences among treatments in ‘Beliana’, except after 5 d where all treatments where firmer than control. The ‘Lindo’ apricots treated with 3 and 5% CaCl2 showed higher firmness values than the other treatments through storage, except at 28 d where only the 5% CaCl2 had significantly higher firmness. ‘Beliana’ did not show differences in SSC among treatments. However, ‘Lindo’ had lower SSC when treated with 1% CaCl2. When tested after 27 d storage, panellists preferred fruit from the 1% CaCl2 treatment followed by the control for both cultivars. It seems that CaCl2 treatments with concentrations over 3% are prejudicial for apricots. Concentrations between 1 and 3% should be assayed, since 1 and 3% look to be beneficial for the different quality parameters.