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- 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.
- 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.
- Impact of water heat treatment on physical-chemical, biochemical and microbiological quality of whole tomato (Solanum lycopersicum) fruitPublication . Pinheiro, Joaquina; Silva, Cristina L. M.; Alegria, Carla; Abreu, Marta; Sol, Manuela; Gonçalves, Elsa M.Water heat treatments (WHT) are applied to fresh fruits for disinfection purposes as well as to promote changes to the biochemical pathways involved in the ripening process, resulting in remarkable beneficial effects on postharvest quality maintenance and storage life extension. The objective of this study was to evaluate the overall effects of WHT on tomato (Solanum lycopersicum 'Zinac') quality and to determine an optimal WHT condition to extend its shelf-life. Fruits were immersed in hot water at different temperatures (from 40 to 60°C) and during different periods of time (2 to 60 min). WHT effects on fruit colour CIELab parameters (a* and °h), firmness (N), peroxidase (POD) and pectinmethylesterase (PME) enzyme activity, total phenolic content (TPC) and microbial load (mesophylic and yeasts & moulds counts (Y&M)) were evaluated. After WHT no observable color changes were denoted in all heat treated samples. At lower WHT, 40-50°C, maintenance in firmness was obtained when compared to untreated samples. Significant reductions on tomato firmness were observed in treatments with temperatures higher than 55°C. Both evaluated enzymatic activities were affected by the heat treatments. Regarding POD enzyme, an increase in its activity was found with intensive WHT, while PME activity decreased at all tested conditions with two exceptions (45 and 60°C). In fruits treated at 40°C/30 min the highest increase in TPC was found when compared to the control sample (ca. 27%). WHT at 50°C/2 min or 40°C/30 min promoted a reduction in mesophylic and Y&M load to undetectable levels, showing the effectiveness of these treatments to control microbial development in tomato fruits. Therefore, these treatments present an alternative postharvest process for tomato storage with beneficial effects to fruit quality as well as extension of shelf life.
- 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.
- Physical-chemical quality and nutritional composition of tomato (Solanum lycopersicum) fruits as influenced by different factors during postharvest life.Publication . Pinheiro, Joaquina; Gonçalves, Elsa M.; Silva, Cristina L. M.The concept of tomato quality refers to all attributes that consumer consciously or unconsciously believes that the fruit must have. However, it is necessary to expand this concept not only by consumer but also to all who participate in fresh tomato chain, from production to consumption. Producers must pick up fruits with high yielding, resistant to diseases, good and with few defects. Distributors intend to maintain sensory properties and to provide efficient storage, while consumers determine their quality by appearance, consistency, cross-sectional diameter, deformations and injuries absence. Physical-chemical attributes are used to assess quality in fresh tomatoes. Colour, firmness, flavour and nutrition value are important quality indicators. Colour is considered a major attribute of tomatoes and relates primarily to the lycopene content. Tomato colour should be uniform and textural quality of tomatoes is influenced by flesh firmness. Firmness changes are highly correlated with tomatoes surface appearance properties which are related to colour, shape and sense of firmness feel at the time of purchasing. Flavour is the function of taste and aroma components. The relationship between the acidity and soluble solids of tomato fruit is critical to its perceived flavour. Good aroma and taste are important factors that influence tomato commercialization. In recent years, consumers have complained about poor flavour in tomato. They consider the new long-shelf life cultivars less tasty than the traditional ones, and would pay higher prices for a product with better flavour quality. Tomatoes are a valuable source of several health-promoting compounds due to the balanced mixture of minerals, micronutrients and antioxidants, including vitamins C and E, carotenoids, potassium, folate, tocopherol, and flavonoids such as quercetin. Tomato fruits are well known for being an economical source of vitamins, with high vitamin C content and also significant amounts of vitamin A and B. It also contains a large amount of water and minerals, such as potassium, magnesium, phosphorous and calcium, with great importance in human metabolic activities. In addition to these well-known phytonutrients, other compounds in tomato fruit with antioxidant properties include chlorogenic acid, rutin, plastoquinones, tocopherol, and xanthophylls. Most of these nutrients in tomatoes confer a preventive benefit against oxidative stress-associated diseases, through various mechanisms, including antioxidant action. Postharvest period begins at the separation of plant used as food from the medium of its immediate growth or production, and ends when it enters the preparation process for final consumption or further preservation. Quality deterioration of harvested fruits is the result of a combination of physiological, mechanical, microbiological and environmental factors and conditions. In view of the important role that the tomato plays in the human diet, the quality and nutritional composition of tomato fruit and important aspects that influence its quality are discussed in this chapter.