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- Avoiding high relative air humidity during critical stages of leaf ontogeny is decisive for stomatal functioningPublication . Fanourakis, Dimitrios; Carvalho, Susana M. P.; Almeida, Domingos M. P.; Domingos, P.F.; Heuvelink, EpPlants of several species, if grown at high relative air humidity (RH >= 85%), develop stomata that fail to close fully in case of low leaf water potential. We studied the effect of a reciprocal change in RH, at different stages of leaf expansion of Rosa hybrida grown at moderate (60%) or high (95%) RH, on the stomatal closing ability. This was assessed by measuring the leaf transpiration rate in response to desiccation once the leaves had fully expanded. For leaves that started expanding at high RH but completed their expansion after transfer to moderate RH, the earlier this switch took place the better the stomatal functioning. Leaves initially expanding at moderate RH and transferred to high RH exhibited poor stomatal functioning, even when this transfer occurred very late during leaf expansion. Applying a daily abscisic acid (ABA) solution to the leaves of plants grown at continuous high RH was effective in inducing stomatal closure at low water potential, if done before full leaf expansion (FLE). After FLE, stomatal functioning was no longer affected either by the RH or ABA level. The results indicate that the degree of stomatal adaptation depends on both the timing and duration of exposure to high RH. It is concluded that stomatal functionality is strongly dependent on the humidity at which the leaf completed its expansion. The data also show that the effect of ambient RH and the alleviating role of ABA are restricted to the period of leaf expansion.
- Effect of modified atmosphere on phytochemical profile of pasteurized peach puréesPublication . Oliveira, Ana; Coelho, Marta; Alexandre, Elisabete; Gomes, Maria Helena; Almeida, Domingos P. F.; Pintado, ManuelaPeach phytochemical profile was analysed during 90 days storage under three different gas mixtures: 10 kPa O2+90 kPa N2, 100 kPa N2 and air (78 kPa N2+21 kPa O2+0.03 kPa CO2) for both 4 and 23 °C. The antioxidant activity increased when peach purée was stored under air at 4 °C and 100 kPa N2 at 23 °C, while total phenolic content was not affected by atmospheres. Total carotenoids were more stable for 100 kPa N2, where it decreases 48 and 58% respectively for 4 and 23 °C. The content of (+)-catechin decreased 42% for 10 kPa O2 at 4°C, remaining constant in other atmospheres. Chlorogenic and neochlorogenic acids were well preserved in atmospheres containing oxygen, presenting an increase of 14 and 24% for 10 kPa O2 at 4°C. The higher content of carotenoids was obtained for 100 kPa N2 at 23 °C. Principal component analysis shows that atmospheres variance was associated with carotenoids while storage time was more related with total phenolics and total antioxidant capacity.
- Long-term frozen storage and pasteurization effects on strawberry polyphenols contentPublication . Oliveira, Ana; Coelho, Marta; Alexandre, Elisabete M. C.; Almeida, Domingos P. F.; Pintado, ManuelaThe profile of the strawberry polyphenols was analysed on fresh strawberry, immediately after freezing or after pasteurization and during frozen storage of strawberry at -20 A degrees C for 360 days. Freezing increased the extractability of (-)-epigallocatechin gallate (60 %), (-)-epicatechin (48 %) and ellagic acid (51 %) and decreased the pelargonidin-3-glucoside (18 %). Direct pasteurization of fresh strawberry increased the extractability for (-)-epigallocatechin gallate (73 %), (-)-epicatechin (45 %) and ellagic acid (143 %) and decreased for pelargonidin-3-glucoside (16 %). During storage at -20 A degrees C for 360 days the extractable levels of pelargonidin-3-rutinoside, (-)-epigallocatechin gallate, (+)-catechin, (-)-epicatechin and ellagic acid decreased by 17, 20, 37, 65 and 80 %, respectively, while those of pelargonidin-3-glucoside increased 13 %. Changes in polyphenols content, produced by pasteurization after 360 days frozen storage, were minimal. Polyphenols content decreased during storage of strawberry pieces at -20 A degrees C for 360 days, while the thermal treatment applied after freezing storage did not induce any significant change.
- Phytochemicals preservation in strawberry as affected by pH modulationPublication . Oliveira, Ana; Gomes, Maria Helena; Alexandre, Elisabete M. C.; Poças, Fátima; Almeida, Domingos P. F.; Pintado, ManuelaStrawberries purees are incorporated in foods and subjected to pH modulation according to the expected final food matrix. The effect of pH on strawberry polyphenols stored at 4 and 23 degrees C for 90 days was evaluated. Total antioxidant activity and total phenolics content were only affected by time according to a first order model. The pH 4.5 induced higher decrease in (-)-epigallocatechin gallate (71% and 79%) and quercetin-3-glucoside (29% and 36%), for both storage temperatures. For pH 2.5 and 3.0, ellagic acid increased 84% for 4 degrees C. and 185% for 23 degrees C. Anthocyanins concentration changes along storage were well described by first order model. The pH value of 2.5 presented the lower kinetic constant rate where cyanidin-3-glucoside, pelargonidin-3-glucoside and pelargonidin-3-rutinoside had a k = 0.04, 0.05 and 0.03 day(-1). Lower storage temperature (4 degrees C) and lower pH (2.5) were the best condition for the preservation of polyphenols in pasteurized strawberry during a 90-day storage period.
- Differential responses of the antioxidant defence system and ultrastructure in a salt-adapted potato cell linePublication . Queirós, Filipa; Rodrigues, José A.; Almeida, José M.; Almeida, Domingos P. F.; Fidalgo, FernandaChanges in lipid peroxidation and ion content and the possible involvement of the antioxidant system in salt tolerance at the cellular level was studied in a potato (Solanum tuberosum L.) callus line grown on 150 mM NaCl (salt-adapted) and in a non-adapted line exposed to 150 mM NaCl (salt-stressed). Salinity reduced the growth rate and increased lipid peroxidation in salt-stressed line, which remained unaltered in the adapted line. Na+ and Cl− content increased due to salinity in both lines, but the adapted line displayed greater K+/Na+ ratio than the stressed one. Total superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), and glutathione reductase (GR, EC 1.6.4.2) activities decreased in both salt-exposed lines; catalase (CAT, EC 1.11.1.6) activity did not change in the adapted line, but decreased in the stressed cell line. Salinity caused the suppression of one GR isoform, while the isozyme patterns of SOD, APX, and CAT were not affected. Ascorbate and reduced glutathione increased in both salt-exposed calli lines. α-Tocopherol increased as a result of salt exposure, with higher levels found in adapted calli. Electron microscopy showed that neither the structural integrity of the cells nor membrane structure were affected by salinity, but plastids from adapted cells had higher starch content. The results suggest that the enzymic and non-enzymic components of the antioxidant system are differentially modulated by salt. Different concentrations of antioxidant metabolites are more relevant to the adaptive response to salinity in potato calli than the differences in activity of the antioxidant enzymes.
- Modelling respiration of packaged fresh-cut "Rocha" pear as affected by oxygenPublication . Gomes, M. Helena; Beaudry, Randolph M.; Almeida, Domingos P. F.; Malcata, F. XavierRespiration rates were measured in fresh-cut ‘Rocha’ pear (Pyrus communis L.) stored at four temperatures (0, 5, 10 and 15 C) and with oxygen partial pressures ranging from 0 to 18 kPa. Respiratory quotient and ethanol production were used to determine the fermentation threshold. The oxygen concentration effect on the respiration rate was accurately described using Michaelis–Menten kinetics, without noncompetitive inhibition by CO2, and the effect of temperature on the respiration rate was well modelled by exponential functions. The oxygen level at which respiration was half its maximum (apparent Km;O2 ) was similar to or only slightly greater than the fermentation threshold. The narrow range of oxygen between Km;O2 and the fermentation threshold, suggests that modified atmosphere packaging technology has a limited applicability toward extension of the shelf-life of fresh-cut ‘Rocha’ pear.
- Quality changes in fresh-cut ‘Rocha’ pear as affected by oxygen levels in modified atmosphere packaging and the pH of antibrowning additivePublication . Gomes, M. Helena; Fundo, Joana F.; Poças, M. Fátima; Almeida, Domingos P. F.Respiratory behavior of fresh-cut ‘Rocha’ pear suggests that optimization of O2 concentration inside modified atmosphere packages (MAP) is of limited benefit. To test this hypothesis, packages were designed to achieve three equilibrium O2 partial pressures. Fresh-cut ‘Rocha’ pear was treated with 250 mM calcium ascorbate solutions buffered at pH 3.0 and pH 7.0, packaged under the three MAP conditions, and stored at 5 ◦C for 20 d. Actual O2 levels (mean ± confidence interval at 95%) during the experiment were 16.7 ± 0.2, 1.8 ± 0.2 and 0.25 ± 0.04 kPa with corresponding CO2 levels of 1.3 ± 0.1, 4.3 ± 0.2 and 6.5 ± 0.4 kPa. Changes in quality attributes related to fruit metabolism, namely firmness, titratable acidity, pH, and soluble solids content were not affected by O2 levels. Overall changes in water activity, levels of ascorbate, and microbial growth were also independent of O2 levels. Oxygen partial pressure inside the packages affected browning, which was more intense at 16.7 kPa O2. Sensory analyses performed after 8 d in storage confirmed that panelists perceived the differences in color but did not detect differences in firmness or taste among the samples under different O2 levels. Browning was more intense at pH 3.0 than at pH 7.0 but the kinetics of other quality attributes were not affected by pH. No significant improvements of quality attributes dependent on the physiology of respiration of fresh-cut ‘Rocha’ pear can be obtained by reducing O2 partial pressure inside the packages.
- Antioxidant properties and fruit quality during long-term storage of “rocha” pear: effects of maturity and storage conditionsPublication . Silva, Filipe J. P.; Gomes, Maria Helena; Fidalgo, Fernanda; Rodrigues, José A.; Almeida, Domingos P. F.Free radical scavenging activity and the content of ascorbic acid and glutathione were investigated during long-term storage of the pear (Pyrus communis L. ‘Rocha’) fruit harvested at different maturity stages, stored in air or under controlled atmosphere and subjected to postharvest treatments with diphenylamine (DPA) and 1-methylcyclopropene (1-MCP). Harvest maturity had a significant effect on storage disorders, fruit firmness, soluble solids content and acidity. Differences in ascorbate content and free radical scavenging activity at harvest did not persist during storage. Controlled atmosphere and DPA strongly reduced the incidence and severity of browning disorders and superficial scald, whereas 1-MCP provided the most effective control. Neither DPA nor 1-MCP affected the free radical scavenging activity
- Incorporation of strawberries preparation in yoghurt: impact on phytochemicals and milk proteinsPublication . Oliveira, Ana; Alexandre, Elisabete M. C.; Coelho, Marta; Lopes, Cláudia; Almeida, Domingos P. F.; Pintado, Manuela E.An immediate decrease in the total antioxidant activity (23%) and total phenolic content (14%) was observed after addition of strawberry preparations to yoghurt. The total anthocyanin content did not change immediately, but decreased 24% throughout the yoghurt shelf-life. The individual compounds, (+)-catechin (60%), (-)-epicatechin (60%), kaempferol (33%) and quercetin-3-rutinoside (29%) decreased after 24 h in the yoghurt made with the strawberry preparation. During the remaining period of storage these compounds increased by 47%, 6%, 4% and 18%, respectively. Pelargonidin-3-glucoside decreased 49% after 28 d. Immediately after the addition of the strawberry preparation to yoghurt, beta-lactoglobulin decreased to values lower than the limit of detection and alpha-lactalbumin by approximately 34%, and was reduced further slowly throughout yoghurt self-life. An immediate interaction between the carrageenan present in the strawberry preparation and beta-LG was observed. The variations of both polyphenols and protein in the presence of carrageenan and the potential interactions were discussed.
- Effect of postharvest application of ethylene on the profile of phenolic acids and anthocyanins in three blueberry cultivars (Vaccinium corymbosum)Publication . Costa, Daniela V. T. A.; Almeida, Domingos P. F.; Pintado, ManuelaBACKGROUND:Theblueberry is a fruit that hasbeen studied extensively for its healthbenefits,mainlydueto itshigh antioxidant activity. There is a strong correlation between antioxidant activity and total anthocyanin and phenolic compound content. Postharvest treatment using ethylene may be a factor affecting the anthocyanin content. The objective of this work was to analyze postharvest treatment using ethylene on the anthocyanin profile during the storage of blueberries and phytochemical composition of ‘Bluecrop’, ‘Goldtraube,’ and ‘Ozarkblue.’ Fruits were harvested at commercial maturity; the treatment was carried out with 1000 𝛍LL−1 of ethylene for 24 h followed by storage at 4 ∘C under normal atmosphere for 56 days. RESULTS: One day after treatment with ethylene, this increased the proportion of seven (more than 45%) and four (more than 65%) of the nine anthocyanins identified in the Bluecrop and Goldtraube cultivars respectively, and decreased five of the seven anthocyanins identified in ‘Ozarkblue’. For ‘Bluecrop,’ however, this increase reduced until the end of storage but in ‘Goldtraube’ seven anthocyanins had increased. CONCLUSION: The effect of ethylene on anthocyanin composition of blueberries appeared to depend on the cultivar. ‘Bluecrop’ and ‘Goldtraube’ responded positively with an increase in total anthocyanins.