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- Propolis volatiles characterisation from acaricide-treated and -untreated beehives maintained at Algarve (Portugal)Publication . Miguel, Maria Graça; Nunes, S.; Cruz, C.; Duarte, J.; Antunes, Maria Dulce; Cavaco, A. M.; Mendes, M. D.; Lima, A. S.; Pedro, L. G.; Barroso, J. G.; Figueiredo, A. C.The variability of the volatile profile of 70 propolis samples from acaricide-treated and -untreated beehives maintained at Algarve (Portugal) was evaluated. Propolis samples were collected in three regions of Algarve at three different periods. Cluster analysis based on the propolis volatiles' chemical composition defined two main clusters, not related to the time of year, collection site, altitude, temperature or humidity ranges, and was based mainly on the relative amounts of viridiflorol, n-tricosane and n-nonadecane for cluster I. Cluster II was mainly characterised by the high thymol content, followed by viridiflorol, n-tricosane and n-nonadecane. The presence of higher thymol levels in propolis samples from cluster II may reflect the long use of an acaricide with thymol as main active ingredient. All samples showed an intense rock-rose aroma supported by the presence of characteristic Cistus and labdanum oil volatile components. Given the nowadays frequent propolis household use, volatiles thorough characterisation may assist in its quality assessment.
- A possibility for non-invasive diagnosis of superficial scald in 'Rocha' pear based on chlorophyll a fluorescence, colorimetry, and the relation between alpha-farnesene and conjugated trienolsPublication . Guerra, Rui Manuel Farinha das Neves; Garde, I. V.; Antunes, Maria Dulce; da Silva, J. M.; Antunes, Rosário; Cavaco, A. M.This study aimed to identify physiological markers in superficially scalded 'Rocha' pear (Pyrus communis L 'Rocha') that would relate to chlorophyll a fluorescence (CF), allowing a non-invasive diagnosis of the disorder. Conditions chosen before shelf life provided two fruit groups with different developing patterns and severity of superficial scald: T fruit fully developed the disorder in storage, while C fruit developed it progressively throughout shelf life. Principal component analysis (PCA) of all the measured variables, and simple linear correlations among several major parameters and scald index (SI)/shelf life showed that scald and ripening/aging were concurring processes, and that it was not possible to isolate a particular variable that could deliver a direct non-invasive diagnosis of the disorder. For both fruit groups the SI resulted from the balance between the reducing power (OD200) and the content of conjugated trienols (CTos) and alpha-farnesene (alpha-Farn) in the fruit peel. At OD200 > 150 there was a linear relationship between CTos and OD200, suggesting that the level of antioxidants was self-adjusted in order to compensate the CTos level. However, at OD200 < 150 this relationship disappeared. A consistent linear relationship between dos and alpha-Farn existed throughout shelf life in both fruit groups, contrarily to the early storage stage, when those compounds do not relate linearly. The CF variables F-0, F-v/F-m, and the colorimetric variables, L* and h degrees were used in multi-linear regressions with other physiological variables. The regressions were made on one of the fruit groups and validated through the other. Reliable regressions to alpha-Farn and CTos were obtained (R approximate to 0.6; rmsec approximate to rmsep). Our results suggest that a model based on CF and colorimetric parameters could be used to diagnose non-invasively both the contents and the relationship between alpha-Farn and CTos and hence the stage of scald development. (C) 2011 Elsevier By. All rights reserved.
- Chlorophyll a Fluorescence: a Fast and Low-Cost Tool to Detect Superficial Scald in 'Rocha' Pear (Pyrus communis L. 'Rocha')?Publication . Garde, I.; Antunes, Maria Dulce; da Silva, J. M.; Guerra, Rui Manuel Farinha das Neves; Cavaco, A. M.This study aimed to test whether the chlorophyll a (Chla) fluorescence determined by a low-cost non-modulated fluorometer could provide fast, reliable and non-invasive estimators of superficial scald in 'Rocha' pear (Pyrus communis L. 'Rocha'). Fruit were harvested before the optimal maturation stage and cold stored under normal atmosphere for 7 months (NA: 0 degrees C, 90-95% RH) and 2 in controlled atmosphere (CA: 0 degrees C, 90-95% RH, 1.5 kPaO(2) + 0.5 kPa CO2) (T), or harvested at the optimal maturation stage and cold stored for 9 months under CA (C). Then, they were transferred to shelf-life conditions (22+/-2 degrees C, 70% RH) and followed for 7 d. Chla fluorescence, scald index (SI), ripening attributes, alpha-farnesene, conjugated trienols, and photosynthetic pigments were determined for each pear in both groups. Conditions chosen before shelf-life did not prevent the subsequent ripening of any fruit, but changed dramatically the superficial scald development pattern: in C fruit, the disorder developed progressively during shelf-life, whereas in T fruit, it peaked during storage. C fruit exhibited a significant negative correlation (R=-0.65; p<0.05) between Fv/Fm and scald development, but not with ripening (R=-0.15; p<0.05). As expected, the opposite was observed in T fruit, in which only a low, positive, yet significant correlation was found between Fv/Fm and ripening (R=0.44; p<0.05). The multiple regression approach using Fv/Fm and other Chla fluorescence parameters produced an equation from which we calculated the 'predicted' scald index in C fruit. This correlated clearly (R=0.73; p<0.05) with the real values visually assessed. If color values a*, b* and Hue were included in this multiple regression, the correlation was significantly enhanced (0.91; p<0.05). Although preliminary, this study has shown that basic Chla fluorescence parameters are valuable estimators of superficial scald in 'Rocha' pear and might be used in the early detection of the disorder.
- Estimation of soluble solids content and fruit temperature in 'rocha' pear using Vis-NIR spectroscopy and the spectraNet–32 deep learning architecturePublication . Martins, J. A; Rodrigues, Daniela; Cavaco, A. M.; Antunes, Maria Dulce; Guerra, Rui Manuel Farinha das NevesSpectra-based methods are becoming increasingly important in Precision Agriculture as they offer non-destructive, quick tools for measuring the quality of produce. This study introduces a novel approach for esti-mating the soluble solids content (SSC) of 'Rocha' pears using the SpectraNet-32 deep learning architecture, which operates on 1D fruit spectra in the visible to near-infrared region (Vis-NIRS). This method was also able to estimate fruit temperatures, which improved the SSC prediction performance. The dataset consisted of 3300 spectra from 1650 'Rocha' pears collected from local markets over several weeks during the 2010 and 2011 seasons, which had varying edaphoclimatic conditions. Two types of partial least squares (PLS) feature selection methods, under various configurations, were applied to the input spectra to identify the most significant wavelengths for training SpectraNet-32. The model's robustness was also compared to a similar state-of-the-art deep learning architecture, DeepSpectra, as well as four other classical machine learning algorithms: PLS, multiple linear regression (MLR), support vector machine (SVM), and multi-layer perceptron (MLP). In total, 23 different experimental method configurations were assessed, with 150 neural networks each. SpectraNet-32 consistently outperformed other methods in several metrics. On average, it was 6.1% better than PLS in terms of the root mean square error of prediction (RMSEP, 1.08 vs. 1.15%), 7.7% better in prediction gain (PG, 1.67 vs. 1.55), 3.6% better in the coefficient of determination (R2, 0.58 vs. 0.56) and 5.8% better in the coefficient of variation (CV%, 8.35 vs. 8.86).
- Effect of 1-Methylcyclopropene application prior to storage on fresh-cut kiwifruit qualityPublication . Antunes, Maria Dulce; Miguel, Maria Graça; Metelo, S.; Dandlen, S. A.; Cavaco, A. M.Kiwifruit is commercially important as fresh-cut. The purpose of this work was to study the effect of 1-methylcyclopropene (1-MCP) applied after harvest, before storage, on the posterior behaviour of ripe fruit prepared as fresh-cut. Harvested fruit where treated with 1 mu l L(-1) 1-MCP for 20 hours at room temperature, then stored at 0 C. After 3 months, fruit were removed from storage, peeled and cut longitudinally in quarters, then stored at 2 C for 8 days. Measurements of flesh colour, firmness, soluble solids content (SSC), electrolyte leakage and ascorbic acid were performed after 0, 4 and 8 days. Kiwifruit treated with 1-MCP showed higher firmness and lower a* value, electrolyte leakage and SSC than the control, after 3 months storage. Values of a* and electrolyte leakage increased through fresh-cut storage and after 8 days differences between treatments become almost nil. SSC did not change in fruit treated with 1-MCP, while it increased after 4 days and decreased on 8(th) day in the control. Firmness decreased through fresh-cut storage, being higher in 1-MCP treated fruit than control except on 8(th) day. Ascorbic acid which was higher in control, showed a higher decrease on those fruit and after 8 days was similar in both treatments. Panellists did not find significant differences between treatments, except that 1-MCP treated fruit had better appearance. The application of 1-MCP immediately after harvest showed beneficial effects in keeping kiwifruit quality during 3 months storage, and its effect lasted through shelf-life of those fruit when used as fresh-cut.
- Carbon metabolism of Carob young trees under low temperature: different responses among cultivarsPublication . Cavaco, A. M.; Ferreira, V. L.; Santos, A. M.; David, Maria ManuelaYoung trees of two carobs (Ceratonia siliqua L.) cultivars, Mulata and Galhosa, ,propagated in vitro and grown for 3-4 years in a greenhouse were moved into a growth chamber under environmental controlled conditions where they were exposed to 25/15º C (control), 10/5º C (chilling) and again to 25/15º C (recovery).
- Spectral analysis, biocompounds, and physiological assessment of Cork Oak leaves: unveiling the interaction with Phytophthora cinnamomi and beyondPublication . Guerra, Rui; Pires, Rosa; Brazio, António; Cavaco, Ana Margarida; Schütz, Gabriela; Coelho, Ana CristinaThe cork oak tree (Quercus suber L.) symbolizes the Montado landscape in Portugal and is a central element in the country’s social and economic history. In recent decades, the loss of thousands of cork oaks has been reported, revealing the ongoing decline of these agroforestry ecosystems. This emblematic tree of the Mediterranean Basin is host to the soil-born root pathogen Phytophthora cinnamomi, an active cork oak decline driver. In this framework, the early diagnosis of trees infected by the oomycete by non-invasive methods should contribute to the sustainable management of cork oak ecosystems, which motivated this work. Gas exchange and visible/near-infrared (400–1100 nm) reflectance spectroscopy measurements were conducted on leaves of both control and P. cinnamomi inoculated plants. These measurements were taken at 63, 78, 91, 126, and 248 days after inoculation. Additionally, at the end of the experiment, biochemical assays of pigments, sugars, and starch were performed. The spectroscopic measurements proved effective in distinguishing between control and inoculated plants, while the standard gas exchange and biochemistry data did not exhibit clear differences between the groups. The spectral data were examined both daily and globally, utilizing the PARAFAC method applied to a three-way array of samples × wavelengths × days. The separation of the two plant groups was attributed to variations in water content (4v (O−H)); shifts in the spectra red edge; and structural modifications in the epidermal layer and leaves’ mesophyll. These spectral signatures can assist in the field identification of cork oaks that are interacting with P. cinnamomi.
- 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.
- Combined effect of temperature and controlled atmosphere on storage and shelf-life of 'Rocha' pear treated with 1-methylcyclopropenePublication . Gago, Custódia; Miguel, Maria Graça; Cavaco, A. M.; Almeida, Domingos P. F.; Antunes, Maria DulceThe combination of temperature and atmosphere composition for storage of Pyrus communis L. Rocha' treated with 1-methylcyclopropene was investigated. Fruits treated with 312nll(-1) 1-methylcyclopropene were stored at 0? and 2.5? in air and controlled atmosphere (CA) (3.04kPa O-2+ 0.91kPa CO2). Fruits were removed from storage after 14, 26 and 35 weeks, transferred to shelf-life at approximately 22? and assessed for ripening and quality, symptoms of superficial scald and internal browning and the accumulation of biochemical compounds related to scald after 0, 1 and 2 weeks. Superficial scald occurred only in fruits stored for 35 weeks in air at 2.5?. Levels of conjugated trienols and -farnesene increased during the first 26 weeks in storage, remaining constant thereafter. During shelf-life, conjugated trienols were higher in fruits stored in air at 2.5?. Internal browning developed in shelf-life after 26 weeks at 2.5?. Pears in air at 2.5? were not able to stand a 2-week shelf-life after 35 weeks of storage, while fruits stored at 0? under CA ripened slowly after the same storage period. The retention of firmness during shelf-life of 1-methylcyclopropene-treated Rocha' pear can be overcome by elevating the storage temperature from 0? to 2.5?, but CA is a required complement to avoid excessive softening after long-term storage. The ratio carotenoid/chlorophyll increased during storage and shelf-life, as plastids senesced. CA reduced the rate of chlorophyll loss during the first 14 weeks in storage, but its effect was reduced afterwards. Rocha' pear treated with 1-methylcyclopropene had a similar post-harvest behaviour during long-term storage at 0? in air or at 2.5? under CA.
- On the application of spatially resolved reflectance and diffuse light backscattering goniometry to the prediction of firmness in apple ‘bravo de esmolfe’Publication . Guerra, Rui Manuel Farinha das Neves; Almeida, Sandro; Cavaco, A. M.; Antunes, Maria Dulce; Nunes, CarlaIn this study we have made exploratory tests on a set of 40 apples (Malus domestica Borkh.) ‘Bravo de Esmolfe’, using spatially resolved reflectance (SRR) and diffuse light backscattering goniometry (DLBG). The objective was to test the potential of DLBG for firmness prediction, as compared with SRR, whose potential has been already proved in the literature. SRR is performed with a red diode laser and a CMOS camera. DLBG uses the same laser shining on the apple and a photomultiplier tube collecting the light reemitted from a small area, at angles ranging from 90 deg (tangent to the surface) to 180 deg (normal to the surface). From the measurements several parameters have been calculated (e.g. decay exponent for SRR profiles, anisotropy factor for the DLBG angular distributions) and Partial Least squares (PLS) models for the prediction of firmness were build. The model based on DLBG variables (only) and on SRR variables (only) gave similar results. From here we conclude that, within the obvious statistical limitations of the test, DLBG seems to match the potential of SRR for firmness prediction. The possibility of combining both measures in one model is also discussed.
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