Browsing by Author "Almeida, Domingos P. F."
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- 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.
- Physiological bases for texture and color changes in fresh-cut ‘rocha’ pear: implications for the development of products and processesPublication . Gomes, Maria Helena; Almeida, Domingos P. F.; Nunes, CarlaThe physiological bases for the effectiveness of technologies used in fresh-cut fruit were examined in an attempt to foster the shift from a market-pull to a science-push innovation model. Respiration rate of fresh-cut ‘Rocha’ pear were measured at various oxygen concentrations. Apparent Km values for oxygen uptake were very close to the fermentation thresholds, indicating that it is physiologically impossible to reduce the respiration rate of fresh-cut pear by more than 50% without inducing fermentation. Based on this information, we hypothesize that optimizing oxygen concentration inside packages is of little or no value in fresh-cut pears. Additionally, additives used to reduce enzymic browning and softening may have pleiotropic effects on quality. It was found that pH significantly affected the rate and intensity of browning of fresh-cut pears. Browning was more intense in pears treated at pH 3.0 and less pronounced at pH 7.0, but the softening rate was lower at the latter pH value. Calcium salts also affected texture and color in a salt-specific manner. Larger color changes were observed with propionate and lactate. Although calcium ascorbate reduced color changes, fruit slices treated with this salt were softer than those treated with calcium propionate, lactate or chloride. Based on the physiological information gathered, we will develop and evaluate an integrated process to maximize the quality of fresh-cut ‘Rocha’ pear throughout the distribution chain.
- Root-to-shoot ABA signaling does not contribute to genotypic variation in stomatal functioning induced by high relative air humidityPublication . Carvalho, Dália R. A.; Fanourakis, Dimitrios; Correia, Maria João; Monteiro, José; Araújo-Alves, José Pedro L.; Vasconcelos, Marta W.; Almeida, Domingos P. F.; Heuvelink, Ep.; Carvalho, Susana M. P.High relative air humidity (RH >= 85%) during leaf expansion hampers stomatal responsiveness to closing stimuli, a genotype-dependent effect. Genotypes with reduced stomatal closure in response to closing stimuli (i.e., sensitive genotypes) show low bulk leaf abscisic acid concentration ([ABA]). We hypothesized that the amount of ABA produced in the roots and delivered with the transpiration stream to the leaves is a critical step for a proper stomatal functioning in high RH-grown plants. Ten genotypes from a cut rose tetraploid population were grown at moderate (62%) or high (89%) RH. Stomatal anatomy and responsiveness to desiccation or ABA feeding were evaluated. Root and leaf petiole xylem sap [ABA] were quantified, and ABA delivery rate from root-to-shoot was estimated. High RH reduced stomatal responsiveness to both closing stimuli in the sensitive genotypes, whereas it had a nonsignificant effect in the tolerant ones. Estimates of [ABA] in root xylem sap at transpirational flow rate were not related to the genotypic differences in the sensitivity to high RH. However, high RH increased this concentration irrespective of the genotype, probably due to a reduced dilution of the [ABA] in the xylem sap as a result of a lower transpiration rate compared to moderate RH-grown plants. Leaf petiole xylem sap [ABA] was neither related to the genotypic differences in the sensitivity to high RH nor it was affected by RH. We concluded that genotypic differences in the stomatal sensitivity to high RH cannot be explained by changes in the [ABA] delivered with the transpiration stream from the roots to the leaves. (C) 2015 Elsevier B.V. All rights reserved.
- Volatile and quality changes in fresh-cut cantaloupe and honeydew melons stored in modified atmosphere packagingPublication . Amaro, Ana L.; Beaulieu, John C.; Stein, Rebecca E.; Almeida, Domingos P. F.; Nunes, CarlaModified atmosphere packaging (MAP) in fresh-cut melons has been reported to preserve the visual quality during storage, yet its effect upon aroma and firmness is cultivar-dependent. The main objective of this research was to compare the properties of fresh-cut from a fast senescing cantaloupe with a slow senescing honeydew melon, regarding changes in quality and volatiles, when stored in passive MAP. Freshcut cubes of cantaloupe and honeydew melons were packaged in polypropylene trays, over-wrapped with a microperforated film and stored for 14 days at 5 ºC. Three replicate packages of each cultivar were assayed at day 0, 4, 7, 11 and 14 for color, firmness, soluble solid content (SSC), respiration rate and volatile retention, and the experiment was repeated. Volatile compounds were extracted using a relatively recent technique, Stir Bar Sorptive Extraction (SBSE), and quantified via GC-MS. Color and SSC remained constant throughout storage. During the first 4 days of storage, the cantaloupe cubes softened at a higher rate (2.0 N day-1) than honeydew cubes (0.9 N day-1), but firmness remained relatively unchanged thereafter until the end of the storage period. Fresh-cut cantaloupe cubes exhibited a higher respiration rate (17.5-43.4 mL CO2 kg-1 h-1) than fresh-cut honeydew cubes (7.7–30.0 mL CO2 kg-1 h-1), throughout the entire storage period. Esters and aldehydes were the major volatile compounds present in the samples of both cultivars, but cantaloupe yielded higher concentrations of esters and aldehydes, and lower concentrations of alcohols than honeydew. Esters increased their levels during storage, whereas alcohols and aldehydes decreased.