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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.
- Use of UV-C postharvest treatment for extending fresh whole tomato (Solanum lycopersicum, cv. Zinac) shelf-lifePublication . Pinheiro, Joaquina; Alegria, Carla; Abreu, Marta; Gonçalves, Elsa M.; Silva, Cristina L. M.The effect of UV-C treatments (0.32, 0.97, 2.56, 4.16 and 4.83 kJ.m(-2) at 254 nm) on the physical-chemical properties [colour, texture, total phenolic content (TPC), weight loss (WL)], and mesophylic counts of whole tomato, was evaluated during 15 days at 10 A degrees C. During storage, the Ctr samples acquired faster red colour than all UV-C samples (higher a* and lower A degrees h values). Comparing texture of Ctr and UV-C samples at 15(th) storage day, an increase of 9 and 8 % on firmness of treated samples at low UV-C intensities (0.32 and 0.97 kJ.m(-2), respectively) was observed. At the end of the storage, Ctr samples showed ca. 4 Log(10) of mesophylic load, and the samples treated at 0.97 and 4.83 kJ.m(-2) revealed the lowest microbial load (1.9 and 3.2 Log(10), respectively). These results indicate that UV-C radiation, at an appropriate dose, combined with low storage temperature (10 A degrees C) are an effective method to preserve the postharvest life of tomato, without adversely affecting quality parameters.