ESB - Contribuições em Revistas Científicas / Contribution to Journals
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Browsing ESB - Contribuições em Revistas Científicas / Contribution to Journals by Author "Abreu, M."
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- Biochemical and colour changes of watercress (Nasturtium officinale R. Br.) during freezing and frozen storagePublication . Gonçalves, E.M.; Cruz, R.M.S.; Abreu, M.; Brandão, Teresa R. S.; Silva, Cristina L.M.The effects of water blanching, freezing, and frozen storage during 400 days at three different temperatures ( 7, 15 and 30 C), on watercress (Nasturtium officinale R. Br.) colour Hunter Lab parameters,chlorophyll degradation, vitamin C content loss and peroxidase (POD) activity were evaluated. The blanching induced significant changes on colour values and chlorophylls and vitamin C contents. POD activity was reduced 85% from its initial value. Freezing did not affect chlorophylls and vitamin C levels, however, promoted significant differences in colour values and POD residual activity. During frozen storage, ascorbic acid (AA) and POD activity Degradations followed first-order kinetics, and colour parameters (LH aH bH, aH/bH, LH aH/bH, LH/aH bH and hue (h0 H)) were successfully described by zero-order kinetics. The storage temperature effect was successfully described by the Arrhenius law. Chlorophylls and dehydroascorbic acid (DHAA) contents were kept constant during frozen storage.
- Carrot (Daucus carota L.) peroxidase inactivation, phenolic content and physical changes kinetics due to blanchingPublication . Gonçalves, E.M.; Pinheiro, J.; Abreu, M.; Brandão, T.R.S.; Silva, C.L.M.The kinetics of peroxidase thermal inactivation, total phenolic content degradation, and colour (CIE L*a*b*) and texture changes were studied in a temperature range of 70–90 C for carrots (Daucus carota L.). Peroxidase inactivation, total phenolic content degradation and the lightness colour (L* parameter) change were successfully described by a first-order reaction model. The redness and yellowness colour (a* and b* parameters, respectively) and texture (firmness and energy parameters) changes presented a fractional conversion kinetic model behavior. The temperature effect was well described by the Arrhenius law. All the blanching conditions recommended to reduce peroxidase inactivation to an acceptable level (90% loss of its original activity) ensured good quality retention. However, to obtain a high quality carrot product a balance must be made between colour and total phenolic content losses. Therefore, blanching at 80 C for 6 min is suggested as a compromise condition to maximize quality. The overall study indicated that colour is a critical parameter to optimize carrot hot water blanching condition.
- Modelling the kinetics of peroxidase inactivation, colour and texture changes of pumpkin (Cucurbita maxima L.) during blanchingPublication . Gonçalves, E. M.; Pinheiro, J.; Abreu, M.; Brandão, Teresa R. S.; Silva, Cristina L.M.The effects of blanching treatment on peroxidase inactivation, colour and texture of pumpkin (Cucurbita maxima L.) were studied in the temperature range of 75–95 C. Peroxidase inactivation followed a first-order Arrhenius model, where the activation energy and rate of the reaction at a reference temperature of 85 C were 86.20 ± 5.57 kJ mol 1 and 0.27 ± 0.01 min 1, respectively. During blanching, pumpkin became darker and softer with processing time. The degradation of colour (evaluated throughout CIE L*a*b* colour system, with chroma index and total colour difference) and texture parameters (firmness and energy) showed a fractional conversion model kinetics, being the temperature effect on kinetic parameters well described by the Arrhenius law. The results of this work are a good tool to further optimise pumpkin blanching conditions.
- Qualidade e transformação da cenouraPublication . Gonçalves, E. M.; Abreu, M.; Brandão, Teresa R. S.; Silva, C. L. M.