Alicia R. Chaves’s research while affiliated with National University of La Plata and other places

In this work, treatments with UV-C light (20 kJ m⁻²) and gaseous ozone (2 mg L⁻¹ O3) were applied to minimally processed rocket (Eruca vesicaria subsp. Sativa) leaves to investigate their effects on the antioxidant capacity and antioxidant system throughout 8 ds at 5 °C. As control, water washing was used. On 8 d, the ascorbic acid content was reduced about 50% both control and treated samples. Treatments with 20 kJ UV-C m⁻² or 2 mg L⁻¹ O3, did not affect the phenolic content neither the total antioxidant capacity, remaining almost constants during storage. The phenylalanine ammonia lyase (PAL) activity had no significant variations during storage, in correlation with the content of phenolics. As to the enzymes involved in the antioxidant system, an increase in its superoxide dismutase (SOD) activity with respect to uncut rocket leaves was detected after the process. In turn, enzymes that remove H2O2 like ascorbate peroxidase (APX) and catalase (CAT) showed no significant changes. During storage at 5 °C, the SOD activity remained unchanged while APX and CAT showed a gradual increase in both treated and untreated samples. In conclusion, the UV-C and ozone treatments applied inhibited the growth of spoilage by bacteria as well as by yeasts, extended shelf-life, without exerting significant additional stress with respect to the cutting stage of the leaves, reason by which they did not trigger a greater activation of the antioxidant system.

Blueberries are a perishable fruit that loses its firmness and weight rapidly after harvest. High concentrations of ascorbic acid (AA) and phenolic compounds such as anthocyanins are important attributes contributing to the quality of the fruit. The aim of this work is to extend the postharvest life of three blueberries cultivars; ‘Mistý and ‘Blue Cuinex́, firm and soft cultivars respectively and ‘Blue Chiṕ with intermediate firmness. The fruit was treated separately or in combination with a nitric oxide donor, S-nitrosoglutathione (GSNO) and 1-methylcyclopropene (1-MCP) and stored at 4 °C for 14 d. The best treatment for ‘Blue Cuinex́ was the combination of 1-MCP and GSNO, while ‘Mistý softened slower when treated with 1-MCP, and ‘Blue Chiṕ was not affected by treatment. The 1-MCP + GSNO treatment maintained higher concentrations of AA and GSH in ‘Blue Cuinex́. AA concentrations declined in ‘Mistý but did not respond to GSNO. The combination of 1-MCP and GSNO extended the postharvest life of ‘Blue Cuinex́ by improving the concentrations of AA and glutathione in the berries but not for ‘Mistý. These results demonstrate that blueberry cultivars respond differentially to 1-MCP and nitric oxide, and that the sequence of application could be used to slow fruit softening and maintain antioxidant properties.

Yellowing is the most evident symptom of senescence in green vegetables during postharvest storage. As chlorophyll synthesis is promoted by blue light, illumination would be a clean alternative to maintain healthier vegetables for longer. In this paper was assessed the effect of white-blue light-emitting diodes (WB LED) on outer and inner leaves (OL, IL) of Brussels sprouts during 10 d storage at 22 °C. The treated sprouts showed lower respiration rate and remained greener with a better visual quality, with more than 10 times chlorophylls than controls in OL and 1.6 times in IL towards the end of the storage period. The OL had a higher content of antioxidants (DPPH and ABTS⁺ assays) than the IL, and the treatment increased the AOX only in the OL. Total flavonoids content was higher in OL than IL, and about 20% higher in treated samples at day 10 of storage. The storage of Brussels sprouts under continuous low intensity WB LED was effective in delaying the senescence. The effect of the treatment was visible not only in the leaves exposed to light (OL) but also in the IL. The WB LED lighting would be useful to maintain or improve the quality of Brussels sprouts for both storage and transport.

Los frutos de berenjena son muy ricos en antioxidantes dentro de los vegetales. En el presente trabajo se evaluó la influencia del estado de desarrollo y de las condiciones de almacenamiento sobre el nivel y la estabilidad de los antioxidantes fenólicos de berenjena violeta. El ácido clorogénico (CGA) fue el antioxidante predominante y su contenido se redujo progresivamente con el crecimiento del fruto. Las berenjenas en estados iniciales (“baby”) presentaron una capacidad antioxidante dos veces mayor que los frutos totalmente desarrollados. A continuación se evaluaron los cambios en los antioxidantes de berenjenas completamente desarrolladas durante el almacenamiento a temperatura recomendada (10 °C) y en condiciones de daño por frío (0 °C). A diferencia de lo que ocurre en otros productos en los que prevalecen los procesos degradativos, los antioxidantes se incrementaron después de 14 d a 10 °C. Contrariamente los frutos almacenados a 0 °C, mostraron una marcada degradación. Esta caída se relacionó con la aparición de síntomas de daño por frío y pardeamiento. Finalmente, se evaluó la distribución y estabilidad de los antioxidantes fenólicos en la pulpa de berenjenas durante el almacenamiento a 10 °C por períodos prolongados. El CGA se acumuló preferencialmente en la zona interior de la pulpa, su contenido s e incrementó en esta zona hasta los 14 d, mientras que luego de 30 d disminuyó significativamente. Este comportamiento a temperatura recomendada se dio en ausencia de pardeamiento, lo que sugiriere que el CGA se estaría re - direccionando a otros destinos metabólicos. Los resultados obtenidos contribuyen al conocimiento de cómo las condiciones de cosecha y poscosecha tienen implicancia en el nivel de compuestos bioactivos.

The effects of UV‐C radiation doses (5, 10 and 20 kJ/m²) and gaseous ozone doses (1, 2 and 5 ppm) on microbial growth and quality parameters of fresh‐cut rocket (Eruca vesicaria subsp. Sativa) leaves throughout 12 days at 5C were investigated. As control, washing with water was used. Sensory attributes (general appearance, decay, color and odor), headspace gas composition, some chemical characteristics (chlorophyll a and b, total chlorophyll and total carotenoids) and microbial counts throughout shelf‐life were studied. Fresh‐cut rocket was not adversely affected by the UV‐C and ozone treatment, maintaining the sensory quality during cold storage. The 20 kJ UV‐C/m² treatment was found to be better than the chlorine and gaseous ozone treatments, in terms of reducing the microbial load in fresh‐cut rocket during 8 days of storage at 5C. Practical Applications The information provided in this study shows that the treatment with UV‐C radiation and gaseous ozone treatment represent a novel technology that could be useful to the industry, allowing surface decontamination of fresh‐cut rocket to be achieved while maintaining their overall quality. Its applications can easily be applied in industry.

Light is one of the most important factors modulating processes and sequences in plants life, like fruit ripening and the concentrations of water and lipid soluble antioxidants. The aim of this work was to evaluate the most effective frequency of low irradiance light pulses (LP) during the night and to analyze its effect on plant and fruit growth, as well as on modifications of concentrations of soluble sugar, amino acids, antioxidants and organic acids. LP of 15 min each were applied over the plants in a temperature controlled greenhouse after fruit set till they turned to mature red, with a frequency of 2 and 4 h. LP induced no changes in the typical maturation indexes such as soluble solid, total acidity, pH or firmness; meanwhile there was an 18% increase in fruit yield when plants were exposed to 15 min LP every 2 h during the night. Furthermore, by analyzing the tomato cluster receiving this LP treatment separately, the biomass of the fruit was found to have increased by 28% compared with the same cluster in control plants. In coincidence with this, fruit treated with a frequency of 2 and 4 h LP showed an increase in lycopene concentration, concomitantly with a rise in the proportion of red mature fruit harvested from the whole plant. On the other hand, there was a drop in the concentration of soluble sugars and free amino acids, possibly conducing to a decrease in water soluble antioxidants (ascorbic acid and glutathione) and citric and malic acids concentration. Overall, these results showed that nocturnal LP treatments improved fruit yield in tomato plants with higher amounts of lycopene, which indicate earlier fruit ripening.

The effects of UV-C pretreatments (10, 20 and 30 kJ/m2), compared with modified atmosphere packaging (MAP), on sensory change, microbial and bioactive profile of minimally processed rocket leaves throughout 12 days at 5C were investigated. Nonirradiated samples were used as controls. All UV-C treatments reduced the natural microflora growth. In relation to sensory quality, all treatments resulted in a shelf life of 8 days. Total antioxidant activity and total phenol content decreased after 8 days for all treatments. Generally, UV-C slightly reduced the initial total chlorophyll content; however, during storage, its degradation was similar to that of the control. It is concluded that UV-C pretreatment could be useful to the industry to reduce the natural microflora growth, keeping the overall quality without affecting the bioactive compound profile of fresh rocket leaves during 8 days of storage at 5C.Practical ApplicationsThe information provided in this study shows that the use of UV-C radiation could be a useful tool for the food industry for maintaining the overall quality and safety of fresh rocket leaves, while minimizing water consumption and wastewater discharge rates.