Browsing by Author "Antunes, Maria Dulce"
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- 1-Methylcyclopropene and lemongrass essential oil nanocoatings effect on the preservation of cold stored ‘Rocha’ pearPublication . Gago, Custódia; Guerreiro, Adriana; Cruz, Sandra; Martins, Nuno; Cabrita, Maria João; Miguel, Maria; Faleiro, Maria Leonor; Antunes, Maria DulceThe effects of coating 'Rocha' pear with alginate-based nanoemulsions enriched with lemongrass essential oil (LG) was evaluated and compared to the usual 1-MCP treatment. Fruit were treated with 1-MCP (312 nL L-1) or coated with nanoemulsions: sodium alginate 2 % (w/w) + lemongrass essential oil 1.25 % (w/w) (LG 1.25 %) or lemongrass essential oil 2.5 % (w/w) (LG 2.5 %). Then, fruit were stored at 0 degrees C and 90-95 % relative humidity (RH), for eight months. Fruit samples were collected at harvest and after two, four, six and eight months of cold storage, and then transferred to shelf-life at 22 degrees C. Upon removal and after 7 d shelf-life, fruit symptoms of superficial scald and internal browning, ethylene production, color CIE (L*, hue), firmness, soluble solids content (SSC), titratable acidity (TA), weight loss, electrolytic leakage (EL), antioxidant activity and fatty acids of pear peel, microbial growth and sensory analyses were evaluated. Coatings and 1-MCP reduced fruit color evolution and preserved better firmness than control. Coatings and 1-MCP did not affect SSC and TA. Treatments did not influence the sensory quality. Microbial growth was within the safety limits in all treatments. Treatments with 1-MCP and LG-nanoemulsions were similarly efficient to reduce superficial scald, nevertheless the LG-nanoemulsions showed higher internal disorders after 8 months of storage and LG 2.5 % had higher decay at the same period, similar to control. 1-MCP treated fruit had the lowest softening rate after shelf-life up to 4 months and LG 2.5 % showed higher weight loss. Also, ethylene production was higher in control and LG 1.25 % up to 6 months plus shelf-life, while after 8 months there was no difference among treatments. This study suggests that 1-MCP is the most efficient for preserving quality of 'Rocha' pear for 8 months, while up to 6 months the best effect is obtained with LG 1.25 % nanocoatings.
- 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.
- A Preliminary Approach to the Prediction of 'Rocha' Pear Skin Pigments by Vis/NIR Reflectance SpectroscopyPublication . Cavaco, A. M.; Antunes, Maria Dulce; da Silva, J. M.; Guerra, Rui Manuel Farinha das Neves'Rocha' pear (Pyrus communis L.) is an exclusively Portuguese certified pear cultivar commercialized worldwide. Mature unripe 'Rocha' pears were obtained from COOPVAL (Cadaval, Portugal) after 8 months at -0.5 degrees C, 94-96% RH and CA (2% O-2+0.5% CO2). Then, they were maintained in a dark room at 20+/-2 degrees C and 70% RH to simulate shelf life. For three weeks these fruit were followed along using Vis/NIR reflectance spectroscopy in the wavelength range of 400 to 950 nm, and their colour and firmness were evaluated by standard techniques. 'Rocha' pear firmness decreased significantly during shelf life, paralleled by the yellowing of the fruit skin (increase in a(star) and Hue angle). Pigments were extracted from fruit skin and assayed spectrophotometrically. Both Chla and Chlb contents decreased along ripening in shelf life, while contents of carotenoids remained constant. Vis/NIR reflectance spectra were correlated with the respective fruit skin pigments content by PLS. Prediction models were obtained for Chl (a, b, a+b), but not for carotenoids. Models were reasonably significant in regression terms [r(Chla)=0.898; r(Chlb)=0.897; r(Chla+b)=0.918], but the respective SDR (standard deviation ratio = standard deviation of the validation set/RMSEP)(2.2 (Chla), 2.3 (Chlb), 2.2 (Chla+b)) suggest that only a coarse quantitative prediction is possible for all models. Although Chla model required a higher number of latent variables [Lv(Chla)= 6; Lv(Chlb or Chla+b)= 3], similarity between RMSEC and RMSEP was lower for the other parameters [Chla: 4.6 and 4.6 g m(-2) Chlb: 3.9 and 2.3 g m(-2), Chla+b: 7.3 and 6.7 g m(-2)]. A better performance for these models has been expected, because most of the differences found in the Vis/NIR spectra in shelf life were in the Chl absorption region. However, only a coarse prediction capability was found. Thus, the data obtained suggest that changes on the background around 670 nm decrease the prediction capability of the PLS model and should be further investigated.
- 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.
- Analysis of spatial interpolation for optimising management of a salinized field cultivated with lettucePublication . Panagopoulos, Thomas; Jesus, J.; Antunes, Maria Dulce; Beltrão, JoséThe lack of randomisation in irrigation experiments is usually a disadvantage. The introduction of spatial variable experimental design offers a convenient tool to help solving this problem. In order to understand the variation of some soil physical and chemical properties in an experimental block and its effect on lettuce (Lactuca sauna L.) production, graphical interpretation of those soil properties was done with the use of geostatistics in a geographic information system (GIS). In this work three techniques of geostatistics were used for the creation of several maps of soil properties in an experimental plot cultivated with lettuce. Lettuces were evaluated for individual weight and diameter at the end of the cropping season. The soil properties studied were: total mineral nitrogen, phosphorus, potassium, pH, electric conductivity and saturated soil hydraulic conductivity. The techniques used were: ordinary kriging, inverse distance and Thiessen polygon. Cross validation used to compare the prediction performances of the three geostatistical interpolation algorithms determined that kriging was the best technique for each soil property. Prior to the creation of the maps, semivariograms were produced for each soil property. The maps resulting from the interpolation techniques were introduced in a GIS and their values reclassified. After that, spatial modelling was used to develop a final overlay map from all the information of the analysed soil properties simulating a "lettuce production capability map". This final map was created with the objective to determine which areas in the plot had optimal conditions for lettuce development. It was concluded that the plot did not had an optimal area for lettuce production. Localized problems with soil properties were found that could be solved with simple geographically restricted amendment treatments. Final lettuce yield had high correlation (r(2) = 0.83) with the lettuce capability map derived. (c) 2005 Elsevier B.V. All rights reserved.
- Anthocyanin concentration of "Assaria" pomegranate fruits during different cold storage conditionsPublication . Miguel, Maria Graça; Fontes, C.; Antunes, Maria Dulce; Neves, Alcinda; Martins, D.The concentration of anthocyanins in fruits of "Assaria" pomegranate, a sweet Portuguese cultivar typically grown in Algarve (south Portugal), was monitored during storage under different conditions. The fruits were exposed to cold storage (5 degrees C) after the following treatments: spraying with wax; spraying with 1.5% CaCl2; spraying with wax and 1.5% CaCl2; covering boxes with 25 mu c thickness low-density polyethylene film. Untreated fruits were used as a control. The anthocyanin levels were quantified by either comparison with an external standard of cyanidin 3-rutinoside (based on the peak area) or individual calculation from the peak areas based on standard curves of each anthocyanin type. The storage time as well as the fruit treatment prior to storage influenced total anthocyanin content. The highest levels were observed at the end of the first month of storage, except for the fruits treated with CaCl2, where the maximal values were achieved at the end of the second month. The anthocyanin quantification method influenced the final result. When total anthocyanin was calculated as a sum of individual pigments quantified based on standard curves of each anthocyanin type, lower values were obtained.
- Anti-acetylcholinesterase, antidiabetic, anti-inflammatory, antityrosinase and antixanthine oxidase activities of Moroccan propolisPublication . EL-GEUNDOUZ, Soukaina; S, Azza; Lyoussi, Badiaa; Antunes, Maria Dulce; Faleiro, Maria Leonor; Miguel, MariaBiological properties of Moroccan propolis have been scarcely studied. In the present work, the total phenols and flavonoids from 21 samples of propolis collected in different places of Morocco or 3 supplied in the market were determined, as well as the invitro capacity for inhibiting the activities of acetylcholinesterase, -glucosidase, -amylase, lipoxygenase, tyrosinase, xanthine oxidase and hyaluronidase. The results showed that samples 1 (region Fez-Boulemane, Sefrou city) (IC50=0.065, 0.006, 0.020, 0.050, 0.014mgmL(-1)) and 23 (marketed) (IC50=0.018, 0.002, 0.046, 0.037, 0.008mgmL(-1)) had the best invitro capacity for inhibiting the -amylase, -glucosidase, lipoxygenase, tyrosinase and xanthine oxidase activities, respectively. A negative correlation between IC50 values and concentration of phenols, flavones and flavanones was found. These activities corresponded to the generally higher amounts of phenols and flavonoids. In the same region, propolis samples have dissimilar phenol content and enzyme inhibitory activities.
- Antimicrobial activity of different nanocellulose films embedded with thyme, cinnamon, and oregano essential oils for active packaging application on raspberriesPublication . Casalini, Sara; Baschetti, Marco G.; Cappelletti, Martina; Guerreiro, Adriana; Gago, Custódia; Nici, Silvia; Antunes, Maria DulceThe study focuses on the antimicrobial activity of nanocellulose films (NFC) embedded with thyme, cinnamon, and oregano essential oils for active packaging application. The activity against model pathogenic bacteria was first tested to obtain each oil's minimum inhibitory concentration (MIC). The tests showed that the surface area of the films and the quantity of essential oil strongly influenced the antimicrobial effect. Then, the different active packaging systems were tested directly on packed raspberries to study their actual commercial packaging conditions. Through 12 days of storage at 1 & DEG;C, it was observed that thyme and oregano essential oils were more effective in maintaining the firmness and reducing the weight loss of the fruits compared to cinnamon essential oil or the control; no significant effect was observed on the other quality parameters that were considered. The essential oils independently proved effective in preventing fungal growth. However, the combined impact of thyme+oregano (NAP_TO) demonstrated the best performance.
- Antimicrobial, antiviral and antioxidant activities of ‘‘água-mel’’ from PortugalPublication . Miguel, Maria Graça; Faleiro, Leonor; Antunes, Maria Dulce; S, Azza; Duarte, Joana; Silvério, Ana R.‘‘Água-mel’’ is a honey-based product produced in Portugal for ancient times. Several attributes have been reported to ‘‘água-mel’’ particularly in the alleviation of simple symptoms of upper respiratory tract. Samples of ‘‘água-mel’’ from diverse beekeepers from different regions of Portugal were studied in what concerns antimicrobial, antioxidant and antiviral properties. The amounts of phenol and brown pigment were also evaluated and correlated with the antioxidant activities. A great variability on the levels of these compounds was found among samples which were responsible for the variability detected also on the antioxidant activities, independent on the method used. Generally, antioxidant activity correlated better with brown pigments’ amount than with phenols’ content. The antimicrobial activity found for ‘‘água-mel’’ samples confirm the virtues reported by popular findings. In addition, this work also reveals the antiviral properties of ‘‘água-mel’’ evidenced by a decrease on the infectivity of the Qb bacteriophage.
- Antioxidant activity of thymbra capitata essential oil in meat-treated oilPublication . Mohammed, A. D.; Miguel, Maria Graça; Antunes, Maria Dulce; Figueiredo, A. C.; Pedro, L. G.; Barroso, J. G.Several synthetic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tertiary butyl hydroquinone (TBHQ), have been used to preserve meat. Nevertheless they are considered toxic and to have carcinogenic effects. Natural products, such as those present in essential oils, have been the target of studies as alternative antioxidants, showing promising results. In addition, these natural compounds have the advantage of having consumer's acceptance. Thymbra capitata is a perennial, herbaceous shrub commonly used as a spicy herb. The essential oils isolated from this plant showed antimicrobial and antioxidant activities. The main goal of the present work was to evaluate the capacity of T. capitata oil to prevent lipid oxidation in bovine meat. Different concentrations of essential oil (0, 50, 75 and 100 mg/5 g of meat) were used in two types of bovine meat samples purchased in the local market. The protein content of both types of meat samples was 21%, and lipid content ranged from 9% to 15%. After covering with the oil, the two types of meat samples were stored at -17 degrees C, for one month. After 1 day, 15 days and 30 days, meat samples were taken and cooked at 85 degrees C for 90 min. The samples were then submitted to the TBARS modified method, for antioxidant activity evaluation. The essential oil was able to prevent meat oxidation even after one month of storage and showed a dose-dependent activity.