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- Kinetics of quality changes of pumpkin (Curcurbita maxima L.) stored under isothermal and non-isothermal frozen conditionsPublication . Gonçalves, E.M.; Pinheiro, J.; Abreu, M.; Brandão, Teresa R. S.; Silva, C. L. M.The effects of freezing process and frozen storage at isothermal (−7, −15 and −25 °C) and non-isothermal (accelerated life testing with step-stress methodology; temperature range from −30 to −5 °C) conditions on pumpkin quality were investigated. Storage temperature conditions were selected to embrace the limits practiced in the cold chain. Quality changes, such as texture, colour CIE Lab and vitamin C (ascorbic acid) content, were evaluated for both frozen storage regimes. The freezing process (that included a pre-blanching step) and subsequent frozen storage had significant impacts on all quality parameters analysed. A fractional conversion kinetic model was adequate in colour, texture and vitamin C data fits. The storage temperature effect was successfully described by the Arrhenius law. This study shows that non-isothermal frozen storage has a marked effect on pumpkin quality.
- Colour and texture evaluation of whole tomatoes (Lycopersicum esculentum L.) at different ripening stagesPublication . Pinheiro, Joaquina; Alegria, C.; Abreu, Marta; Gonçalves, Elsa M.; Silva, Cristina L. M.
- Quality changes of frozen broccoli stored at different temperaturesPublication . Gonçalves, Elsa M.; Pinheiro, Joaquina; Abreu, Marta; Brandão, Teresa R. S.; Silva, Cristina L. M.
- Effect of postharvest treatment (hot water and thermosonication) on tomatoes (Lycopersicum esculentum L.) physical-chemical and nutritional quality during storagePublication . Pinheiro, Joaquina; Alegria, C.; Abreu, Marta; Gonçalves, Elsa M.; Silva, Cristina L. M.
- Evaluation of alternative preservation treatments (water heat treatment, ultrasounds, thermosonication and UV-C radiation) to improve safety and quality of whole tomatoPublication . Pinheiro, Joaquina; Alegria, Carla; Abreu, Marta; Gonçalves, Elsa M.; Silva, Cristina L. M.Previously optimised postharvest treatments were compared to conventional chlorinated water treatment in terms of their effects on the overall quality of tomato (‘Zinac’) during storage at 10 °C. The treatments in question were water heat treatment (WHT = 40 °C, 30 min), ultrasounds (US = 45 kHz, 80 %, 30 min), thermosonication (TS =40 °C, 30 min, 45 kHz, 80 %) and ultraviolet irradiation (UV-C: 0.97 kJ m−2). The quality factors evaluated were colour, texture, sensorial analysis, mass loss, antioxidant capacity, total phenolic content, peroxidase and pectin methylesterase enzymatic activities, and microbial load reduction. The results demonstrate that all treatments tested preserve tomato quality to some extent during storage at 10 °C. WHT, TS and UV-C proved to be more efficient on minimising colour and texture changes with the additional advantage of microbial load reduction, leading to a shelf life extension when compared to control trials. However, at the end of storage, with exception of WHT samples, the antioxidant activity and phenolic content of treated samples was lower than for control samples. Moreover, sensorial results were well correlated with instrumental colour experimental data. This study presents alternative postharvest technologies that improve tomato (Zinac) quality during shelf life period and minimise the negative impact of conventional chlorinated water on human safety, health and environment.
- Modelización del cambio de color y firmeza de tomates (Lycopersicum esculentum L.) a diferentes condiciones del almacenamientoPublication . Pinheiro, Joaquina; Alegria, C.; Abreu, Marta; Gonçalves, Elsa M.; Silva, Cristina L. M.The effect of temperature and storage time on tomatoes (Lycopersicum esculentum L.) colour (a* and ºh) and firmness (maximum force) were analysed at 2º, 5º, 10º, 15º and 20 ºC. The development of these quality attributes followed a fractional kinetic model. The regression coefficient (R2) for the generated models were high, 0.94 for both colour parameters (a* and ºh) and 0.84 for firmness. A significant (p<0.05) increase and decrease for a* and maximum force, respectively, were observed during storage. This study can contribute for the understanding of the real effect of temperature and storage time on two important quality attributes of tomatoes, such as colour and firmness.
- Influence of blanching treatments on colour, texture, chlorophylls content and sensory quality of broccoli (Brassica oleracea L.)Publication . Gonçalves, Elsa M.; Pinheiro, Joaquina; Abreu, Marta; Brandão, Teresa R. S.; Silva, Cristina L. M.
- Postharvest quality of refrigerated tomato fruit (Solanum lycopersicum, cv. Zinac) at two maturity stages following heat treatmentPublication . Pinheiro, Joaquina; Alegria, C.; Abreu, Marta; Sol, Manuela; Gonçalves, Elsa M.; Silva, Cristina L. M.
- Degradation kinetics of peroxidase enzyme, phenolic content, and physical and sensorial characteristics in broccoli (brassica oleracea L. ssp. Italica) during blanchingPublication . Gonçalves, Elsa M.; Pinheiro, Joaquina; Alegria, C.; Abreu, Marta; Brandão, Teresa R. S.; Silva, Cristina L.M.The effects of water blanching treatment on peroxidase inactivation, total phenolic content, color parameters [-a*/b* and hue (h *)], texture (maximum shear force), and sensory attributes (color and texture, evaluated by a trained panel) of broccoli (Brassica oleracea L. ssp. Italica) were studied at five temperatures (70, 75, 80, 85, and 90 C). Experimental results showed that all studied broccoli quality parameters suffered significative changes due to blanching treatments. The vegetal total phenolic content showed a marked decline. Degradation on objective color and texture measurements and alterations in sensorial attributes were detected. Correlations between sensory and instrumental measurements have been found. Under the conditions 70 C and 6.5 min or 90 C and 0.4 min, 90% of the initial peroxidase activity was reduced. At these conditions, no significant alterations were detected by panelists, and a small amount of phenolic content was lost (ca. 16 and 10%, respectively). The peroxidase inactivation and phenolic content degradation were found to follow first-order reaction models. The zero-order reaction model showed a good fit to the broccoli color (-a*/b* and h *), texture, and sensory parameters changes. The temperature effect was welldescribed by the Arrhenius law.
- Descontaminação em hortofrutícolas inteirosPublication . Pinheiro, Joaquina; Alegria, C.; Abreu, Marta; Gonçalves, Elsa M.; Moldão-Martins, Margarida; Silva, Cristina L. M.