Browsing by Author "Sol, Manuela"
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- 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.
- 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.
- Postharvest quality of refrigerated tomato fruit (solanum lycopersicum, cv. zinac) at two maturity stages following heat treatmentPublication . Pinheiro, Joaquina; Alegria, Carla; Abreu, Marta; Sol, Manuela; Gonçalves, Elsa M.; Silva, Cristina L. M.This study evaluated the effect of water heat treatment (WHT, immersion in a water bath at 40C - 30 min) application in alternative to the conventional decontamination treatment of chlorinated water (150 ppm at 5C, pH 6.5 during 2 min) on tomato (cv. Zinac) at two maturity stages (turning and pink). Physiochemical attributes, enzymatic activities and microbial load were evaluated after treatments and during 14 days of storage at 10C. The WHT applied was very effective on microbial reduction and delayed physiochemical changes of tomato, namely firmness loss and red color development during storage period, especially at turning maturity stage. Based on the firmness parameter, shelf-life of control and WHT samples were determined. Our results provide strong evidence that postharvest WHT (40C - 30 min) for tomato fruits at turning maturity stage guarantees the overall quality at 10C twice as long of fruits washed with chlorinated water.
- Safety of frozen vegetables: a case study on carrotsPublication . Gonçalves, Elsa M.; Abreu, Marta; Sol, Manuela; Brandão, Teresa R. S.; Femandes, Isabel; Silva, Cristina L. M.
- Safety of frozen vegetables: a case study on carrotsPublication . Gonçalves, Elsa M.; Abreu, Marta; Sol, Manuela; Fernandes, Isabel; Silva, Cristina L. M.Consumers are confident in frozen foods, which is a consequence of proven safety and quality characteristics of the products. However, safety depends strongly on the quality of the raw materials, the hygienic conditions when handling both at industrial and home processing, and on the temperature conditions during the entire logistic chain. Bacteria survival depends upon a number of factors, such as type of microorganism, freezing process, rate of freezing, storage temperatures and freeze-thaw cycles. The goal of this work was to quantify the impact of the freezing operation per si and frozen storage, at two temperatures (-7º and –20 ºC), on total aerobes, yeast and moulds levels on shredded carrots (Daucus carrota L.). Results showed that, for both temperatures analyzed, the freezing operation itself had a significant effect (p<0,05) in reducing microbial counts, when compared with the initial levels. Storage temperature did not influence significantly mesophilic aerobic flora levels (p<0,05). However, yeasts counts in samples stored at –20ºC presented a gradual decline along the storage period, being significantly lower than samples at -7ºC, after 10 days of storage. Moulds were not detected in all analyzed samples.