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- Shelf life of minimally processed apple (cv. Jonagored) determined by colour changesPublication . Rocha, A. M. C. N.; Morais, A. M. M. B.Physical, chemical and sensory changes of cut apple (cv. Jonagored) stored in the dark at 4 °C were evaluated. Colour was found to be the critical parameter for this product. Apple cubes underwent severe surface browning primarily during the initial days of storage. The shelf-life of cut apple was therefore very limited, to three days maximum. Sensory analyses and objective quality evaluations of cut apple were considered highly correlated in terms of colour and flavour, especially with respect to fructose and sucrose, showing that the selected sensory attributes were good indicators of overall fruit quality.
- Modified atmosphere package for apple ‘Bravo de Esmolfe’Publication . Rocha, A.M.C.N.; Barreiro, M.G.; Morais, Alcina M. M. B.Apple Bravo de Esmolfe original from the parish of Esmolfe is cultivated in specific regions of Portugal. This cultivar of medium to low production requires very low temperatures, but it is extremely sensitive to frost. The aim of this work was to evaluate the influence of modified atmosphere on the quality of apple (cv. Bravo de Esmolfe) during cold storage. Apples packed in modified atmosphere lost less weight, presented better colour, and preserved better firmness than fruits stored in air.
- Characterisation of ‘Starking’ apple polyphenoloxidasePublication . Rocha, Ada M. C. N.; Cano, M. Pilar; Galeazzi, Maria A. M.Experiments were performed to optimise the extraction conditions of “StarkingÏ apple fruit polyphenoloxidase (PPO), to evaluate the affinity and speciÐcity towards several substrates and to study the stability of enzyme extracts from apple samples stored under di†erent conditions. Sodium phosphate bu†er (0É2 M, pH 6É5) plus 0É25% Triton X and 1% or 2% PVPP was found to be the most efficient extraction mediu10m0. Chlorogenic acid, dopamine and 4- methylcatechol showed similar speciÐcity towards PPO, and chlorogenic acid was found to be the best substrate for the enzyme. Enzyme extracts from frozen cut apple stored at [4¡C, and extracts from lyophilised apple samples stored at 4¡C were more stable than extracts obtained from fresh-cut or acetone powder samples
- Influence of controlled atmosphere storage on polyphenoloxidase activity in relation to colour changes of minimally processed ‘Jonagored’ applePublication . Rocha, A. M. C. N.; Morais, M. M. B.The effects of the storage atmosphere composition (2% O2 + 4% CO2; 2% O2 + 8% CO2; 2% O2 + 12% CO2) on polyphenoloxidase activity and phenolic content of the ‘Jonagored’ apple variety during cold storage was evaluated, and the relationship with enzymatic browning investigated. Controlled atmosphere storage inhibited the polyphenoloxidase (PPO) activity of apple cubes during storage. It seems that the higher the concentration of carbon dioxide in the storage atmosphere the higher inhibition of PPO and the lower browning achieved. At the substrate-enzyme levels investigated, the phenolic content, substrate level was the major factor determining darkening.
- Characterization on extraction conditions for 'starking" apple polyphenolox1dase (ppo)Publication . Rocha, A. M. C. N; Cano, M. P.; Galeazzi, A. M.; Morais, Alcina M. M. B.
- Characterization of polyphenoloxidase (PPO) extracted from "Jonagored" applePublication . Rocha, A.M.C.N.; Morais, A. M. M. B.Polyphenoloxidase (PPO) was extracted from apple (cv. Jonagored) with addition of 2% PVP and 0.25% Triton X100 to the extraction buffer containing phenolic adsorbents. Experiments were performed to evaluate the affinity and specificity towards several substrates. ‘Jonagored’ apple PPO was found to have higher specificity (lower Km) towards L-dopa, 4-methylcatechol and (+) catechin than other phenols tested, but the highest activity level was obtained with p-cresol. The ratio Vmax/Km indicates that p-cresol followed by L-dopa and 4-methylcatechol are the best substrates for ‘Jonagored’ apple PPO. The enzyme activity showed two pH optima, at 5.0 and 7.5, at room temperature, with the main peak at pH 7.5 and the secondary one at pH 5.0 when catechol was the substrate.