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  • A TSS classification study of 'Rocha' pear (Pyrus communis L.) based on non-invasive visible/near infra-red reflectance spectra
    Publication . Bexiga, Florentino; Rodrigues, Daniela; Guerra, Rui Manuel Farinha das Neves; Brazio, António; Balegas, Tiago; Cavaco, A. M.; Antunes, Maria Dulce; Valente de Oliveira, JOSÉ
    The 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.
  • Nutritional characterization and storage ability of Salicornia ramosissima and Sarcocornia perennis for fresh vegetable salads
    Publication . Antunes, Maria Dulce; Gago, Custódia; Guerreiro, Adriana; Sousa, Ana Rita; Julião, Miriam; Miguel, Maria Graca; Faleiro, Maria Leonor; Panagopoulos, Thomas
    The aim of this work was to study the potential of two halophytes for fresh salads. Sarcocornia perennis (SAR) and Salicornia ramosissima (SAL) plant tips were harvested in May and July, and stored at 4 °C for 14 days. At harvest, mineral analyses (Na, K, Mg, Ca, P, N, Fe, Zn, Cu, Pb and Cd), chlorophyll content, protein, β-carotene and ascorbic acid were performed. Color (CIELab), phenolics, antioxidant activity and microbial contamination were measured at harvest and after 14 days storage at 4 °C, and a taste panel evaluated the products. SAL had generally slightly higher values of vitamin C, phenols and carotenoids than SAR. In SAR after 14 days of storage, the levels of phenols and the antioxidant activity were higher than at harvest, both in May and July. The opposite was observed for SAL. In this case, only the antioxidant activity was higher after 14 days of storage. Microbial contamination was very low, not reaching even half of critical limits. Both halophytes had good nutritional value, being suitable for use as fresh salads which can be stored for up to 14 days at 4 °C. SAR seems to be a better source of antioxidants, Ca and Fe than SAL and has less general quality and nutritional value changes from harvest time through cold storage. Fresh tips of both halophytes showed better appearance and nutritional quality when harvested in the early season (May) than at the end of the season (July).
  • Membrane fatty acids and physiological disorders in cold-stored ‘Golden Delicious’ apples treated with 1-MCP and calcium chloride
    Publication . Antunes, Maria Dulce; Guimarães, Ana Clara; Gago, Custódia; Guerreiro, Adriana; Panagopoulos, Jorge; Vilas Boas, Eduardo; Miguel, Maria da Graça
    The present research intents to study skin fatty acids and physiological disorders developed during cold storage in ‘Golden Delicious’ apples treated with 1-MCP and calcium. Harvested fruits were treated with calcium chloride (Ca), 1-MCP (MCP), Ca + MCP or no treatment (control) and then subjected to cold storage at 0.5 °C for 6 months. Fatty acids’ composition, malondialdehyde (MDA) and the physiological disorders bitter pit (BP), superficial scald and diffuse skin browning (DSB) were measured at harvest and after storage plus 7 days of shelf-life at room temperature ≈22 °C. Palmitic acid decreased and linoleic acid increased over time, while oleic and stearic acids had few changes. Generally, unsaturated/saturated fatty acids and MDA increased over the storage period. Treatment with Ca showed that, at the end of the experiment, the lowest MDA values and the highest unsaturated/saturated fatty acids ratio were mainly due to higher linoleic and lower palmitic acids concentrations, which are coincident with less severe BP. There was no clear correlation between the measured fatty acids (palmitic, linoleic, oleic and stearic), unsaturated-to-saturated fatty acids ratio or MDA with chilling skin physiological disorders. Further research is needed to clarify the changes in membrane properties and the effect of some treatments in response to chilling injury during storage.
  • 1-Methylcyclopropene and lemongrass essential oil nanocoatings effect on the preservation of cold stored ‘Rocha’ pear
    Publication . Gago, Custódia; Guerreiro, Adriana; Cruz, Sandra; Martins, Nuno; Cabrita, Maria João; Miguel, Maria; Faleiro, Maria Leonor; Antunes, Maria Dulce
    The 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.
  • Quality changes during storage of apricot (prunus armeniaca l.) cv. ‘beliana’ and ‘lindo’ trated with calcium
    Publication . Antunes, Maria Dulce; Miguel, Maria Graça; Neves, M. A.; Cavaco, A. M.; Nunes, Carla
    Calcium 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.
  • Phenols, flavonoids and antioxidant activity of aqueous and methanolic extracts of propolis (Apis mellifera L.) from Algarve, South Portugal
    Publication . Miguel, Maria; Nunes, Susana; Dandlen, Susana Anahi; Cavaco, Ana Maria; Antunes, Maria Dulce
    Propolis is a resinous substance collected by honeybees to seal honeycomb, which has been used in folk medicine due to its antimicrobial and antioxidant properties. In the present study, water and methanol were used to extract phenols and flavonoids from propolis collected in thirteen different areas in the Algarve region during the winter and spring. The ABTS(center dot+), DPPH center dot, and O-2(center dot-) scavenging capacity, and metal chelating activity were also evaluated in the propolis samples. Methanol was more effective than water in extracting total phenols (2.93-8.76 mg/mL) (0.93-2.81 mg/mL). Flavones and flavonols were also better extracted with methanol (1.28-2.76 mg/mL) than with water (0.031-0.019 mg/mL). The free radical scavenging activity, ABTS (IC50 = 0.006-0.036 mg/mL), DPPH (IC50 = 0.007-0.069 mg/mL) and superoxide (IC50 = 0.001-0.053 mg/mL), of the samples was also higher in methanolic extracts. The capacity for chelating metal ions was higher in aqueous extracts (41.11-82.35%) than in the methanolic ones (4.33-29.68%). Propolis from three locations of Algarve region were richer in phenols and had better capacity for scavenging free ABTS and DPPH radicals than the remaining samples. These places are part of a specific zone of Algarve known as Barrocal.